Registration Dossier
Registration Dossier
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EC number: 946-072-5 | CAS number: -
Endpoint summary
Administrative data
Description of key information
Repeated dose toxicity
To address the endpoint repeated-dose toxicity read-across on gluconates and derivatives and iron compounds was performed within the frame of a weight-of-evidence approach.The underlying hypothesis for the read-across is that glucoheptonates and gluconates, structurally similar sugar-like carbohydrate metal-complexes, share the same metabolism pathways in mammals (they are oxidized by pentose phosphate pathway) and that their possible toxicity is a function of the metal cation rather than of the gluconate or glucoheptonate anion.
Therefore, data on iron gluconate, iron EDTA and gluconates and derivatives were taken into account to assess the repeated-dose toxicity of iron glucoheptonate.
On the basis of the available data the registered substance is not classified according to Regulation 1272/2008/EC.
Repeated dose toxicity: oral
Data on iron gluconate
Gluconate and glucoheptonate moieties are very similar and seem to share the same metabolic pathways in mammals. Therefore, the toxicity of iron gluconate and iron glucoheptonate are expected to be at the same level.
Berenbaum et al. (1960) conducted animal experiments, which were designed to compare the toxicologic and hematinic properties of ferrous fumarate with those of ferrous sulphate A.R.,ferrous succinate and ferrous gluconate B.P.C. The ferrous iron contents of these four salts were 33.0, 20.0, 24.8 and 11.7 per cent, respectively. The sulphate was administered as an aqueous solution and the other three compounds as aqueous suspensions containing 0.1 per cent w/v of tragacanth.
The subchronic (12 -weeks) oral toxicities of the four ferrous salts were compared in albino rats of the WAG strain. Ferrous sulphate solution and suspensions of the fumarate, gluconate and succinate containing 20 mg Fe/mL were employed in this experiment. 45 male and 45 female rats (40 -100 g bw) were randomly distributed into nine groups of five males and five females. One group was not dosed and served as controls, while the other eight groups received oral doses of one or other of the iron compounds at a level of 50 or 100 mg Fe/Kg. The animals were individually weighed at intervals and dosed daily, excluding weekends. After 12 weeks’ dosing, the red and total white cell counts and hemoglobin concentrations were determined on two males and two females from each group. All the rats were then killed, and the major organs (liver, spleen, heart, lungs, thymus, kidneys, adrenals, thyroid, testes, prostate, seminal vesicles, ovaries and uterus) were excised, blotted dry, and weighed. The organs from two males and two females from each group dosed at 50 mg Fe/Kg were examined histologically.
Analysis of the combined data showed that at the higher dose level all four compounds significantly depressed growth rate in the male rats, but not in the females. At the lower dose level the depressions produced in the males by the fumarate and the gluconate were not significant (P = 0.05). None of the organ weights (expressed in mg/100 gr bodyweight) in the dosed groups differed significantly (P = 0.05) from those of the controls. Likewise no abnormalities were found in the red or total white cell counts or hemoglobin concentrations. Apart from a slight and variable increase in iron deposition in the tissue phagocytes (e.g., Kupfer cells, pulmonary macrophages and adrenal cortical littoral cells) , histologic examination of the organs listed above revealed no abnormalities that could be attributed to the drugs (Berenbaum et al., 1960).
Taking into account all given data, a NOAEL of 50 mg Fe/kg bw, corresponding to a value of 427.35 mg Ferrous gluconate/kg bw can be established. As mentioned before, Gluconate and glucoheptonate moieties are very similar and seem to share the same metabolic pathways in mammals. Therefore, the value for iron glucoheptonate is assumed to be in the same range as the value for iron gluconate. Thus, the NOAEL of 427.35 mg/kg bw is considered as appropriate for the hazard assessment of iron glucoheptonate.
The acute toxicity of ferrous gluconate (massive hypertherapeutic doses) was determined in direct comparison with that of ferrous sulfate following repeated oral administration in cats for 2 weeks (Hoppe, 1955). Daily doses of 25, 50, 100, 200 and 400 mg/kg of ferrous sulfate and 100, 200, 400, 800 and 1600 mg/kg of ferrous gluconate were administered as a powder by capsule to 2 cats at each dose level 5 days a week for 2 weeks.
All animals were housed in air-conditioned quarters with food and water available at all times, with the exception of the period immediately preceding the oral medications.
No serious body weight changes or mortality occurred among the cats receiving ferrous gluconate. Occasional vomiting and diarrhea occurred at the lower dosages. The intensity of the emesis increased with increase of dosage and was associated with a decrease in the incidence of diarrhea. The emesis appeared to be entirely local in effect, since it occurred in less than an hour after medication. Other than the emesis, the cats appeared to suffer no ill effects from the medication. The appetite except at the highest dosages remained normal in every cat. In this study no NOAEL was identified.
Navas-Carretero (2006) comparatively assessed the bioavailability of two forms of iron, ferrous gluconate or ferric pyrophosphate encapsulated in liposomes (lipofer®), when used as fortificants in meat pate. Ferrous gluconate, sulphate and lactate belong to the group of freely water soluble iron compounds. Thanks to being highly soluble in water, they enter the common pool on non-heme iron completely upon digestion and present high bioavailability. Three groups of growing rats consumed during 28 days either a control diet (AIN-93G), or two diets prepared with enriched pate as the unique source of iron and fat. Body weight and diet intake were measured weekly, and during the last week faeces were collected. On day 28 animals were sacrificed, livers and spleens were removed and stored. Haemoglobin and total iron binding capacity (TIBC) were determined.
There were not significant differences among the three groups in body weight and apparent iron absorption, although food intake in the two pate groups was significantly higher compared to the control group. There were not differences in liver and spleen iron content and concentration, neither in haemoglobin and TIBC values. These results indicated that iron bioavailability of pate enriched with ferrous gluconate or ferric pyrophosphate encapsulated in liposomes was similar.
All these results are also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
Data on gluconates and derivatives
Gluconate and glucoheptonate moieties are very similar and seem to share the same metabolic pathways in mammals. Therefore, the toxicities of gluconates and glucoheptonates are expected to be at the same level.
The SIDS Initial Assessment Report for SIAM 18 (SIDS, 2004) includes various repeated dose data for gluconates and derivatives (SIDS, 2004).
A 28-day study was conducted by feeding rats by gavage with sodium gluconate at doses of 0, 500, 1000, 2000 mg/kg bw in water at a volume of 1 mL/ 100g bw. No death or clinical signs of abnormality were observed in any of the groups. Histopathological examination showed a thickening of the limiting ridge of the stomach in 5 out of 12 males at 2000 mg/kg bw per day dose. No toxic changes associated with the test article were detected. As the limiting ridge is a tissue specific to rodents, this lesion is not toxicologically relevant for humans. Other lesions occurred incidentally and were not treatment -related. The NOAEL was estimated to be 1000 mg/kg bw/day for males and 2000 mg/kg bw/day for females (Mochizuki, M, Bozo Research Center, 1995a).
Another 28-day toxicity study in rats fed with a diet containing up to 5% w/w sodium gluconate (max. 4100 mg/kg bw for males and 4400 mg/kg bw for females) was conducted using a control group receiving equivalent concentration of sodium in the form of NaCl in order to differentiate the potential effects of high doses of sodium intake. No deaths occurred during the study period. No revisions in the general condition, body weight, or food and water intake were observed in the animals over the study period. No changes were observed in the investigated ophthalmologic tests, urinalysis, hematology and blood chemistry over the study period. In addition, histopathological examination indicated no adverse effects as a result of the treatment regime. Statistically significant differences in some urinary parameters reported in animals receiving 2.5 or 5% sodium gluconate were comparable to those observed in the NaCl control group, and were interpreted as related to the high sodium concentration of the diet.
The authors concluded that the NOAEL was 5% (equal to 4100 mg/kg bw per day). However, the JECFA committee who evaluated this report has concluded that the study was not suitable for identifying a NOAEL because of the small group sizes and the positive findings in the qualitative analysis, even if they have acknowledged that the effects shown in the qualitative urine analyses were related to the high sodium intake (Mochizuki, M. Bozo Research Center, 1997, cited in SIDS, 2004). Nonetheless, this study demonstrates the lack of effects of the gluconate anion even in large doses as the urinary effects were attributed to the high sodium intake and was therefore considered as critical for this endpoint.
Repeated toxicity studies were also performed on Beagle dogs with sodium gluconate administered orally for 4 weeks at 500, 1000, 2000 mg/kg bw. doses. None of the animals died during the period of treatment in any dose group and no significantly toxicologically changes were detected in the body weight, food intake, water intake, urinalysis, haematological test, blood chemistry analysis, ophthalmologic test, electrocardiography, autopsy and organ weight or in histopathological examination. However, increased frequency of vomiting and loose or watery stools were observed in the 1000 and 2000 mg/kg bw. dose groups, as compared to controls.
On the basis of these results, the non-toxic dose was estimated to be 500 mg/kg bw / day. However, the toxicological effects observed (vomiting, passage of loose or watery stools) were considered extremely slight since other tests did not show the same changes (Okamoto, M. Bozo Research Center, 1995a).
Glucono-delta-lactone (250, 500, 1000, 2000 and 4000 mg/kgbw for 6 months) was orally administered to Sprague-Dawley rats. In all dose groups, thickening of the stratified squamous epithelium was detected at the anterior stomach, particularly the transitional area continuous with the pyloric stomach; the frequency and severity of this thickening increased with the dose. In high dose groups, submucosal inflammatory cell infiltration was also detected, but this change was not statistically significant. No deaths or other abnormalities were detected (Fukuhara K, 1978). In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug: 1240-1350 mg/kg bw in 2.5% GDL group and 4920-5760 mg/kg bw in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. The NOAEL of sodium gluconate determined from the 28 days studies on rats was equal to 1000 mg/kg bw for males and 2000 mg/kg bw for females. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake provides evidence that no repeated dose toxicity can be attributed to the glucoheptonate moiety of iron glucoheptonate.
Data on sodium ferric ethylenediaminetetraacetic acid (NaFeEDTA)
Rats were administered NaFeEDTA via the food (Appel et al., 2001). No toxicologically significant effects were observed. It can be concluded from this study that the NOAEL is > 84 mg/kg bw/day.
In the study by Yeung et al. (2005) rats received EDTA-FeNa at a level of 1200 mg Fe per kg diet for up to 39 days. Taking into account a consumption of ca. 25 g per day, and a mean weight of ca. 250 g during the study, rats received 30 mg Fe/day or 120 mg Fe/kg bw/day. This corresponds to: 421/56 x 120 = 900 mg EDTA-FeNa.3H2O per kg bw/day. At this level no changes in growth rate were seen. Therefore, the NOAEL most probably is much higher than 84 mg/kg bw day.
These results are also relevant for iron glucoheptonate, as sodium ferric ethylenediamine is similar to iron glucoheptonate, because it is an iron complex as well. Therefore its behaviour in the human or animal body is expected to be similar. Sodium ferric ethylenediaminetetraacetic acid and iron glucoheptonate are therefore considered to be also not acutely toxic according to 1272/2008/EC.
Repeated dose toxicity: inhalation
There are no repeated dose studies available for the inhalation route.
Repeated dose toxicity: dermal
There are no repeated dose studies available for the dermal route.
Key value for chemical safety assessment
Repeated dose toxicity: via oral route - systemic effects
Link to relevant study records
- Endpoint:
- sub-chronic toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the source and the target substance and the expected identical behaviour in the human or animal body. This is based on the fact, that they both are metal complexes consisting of iron and sugar-like carbohydrates that are believed to share the same absorption, distribution and metabolic pathways.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity, 2) the same behaviour in the acidic environment in the stomach and proximal duodenum (dissociation), 3) the same oxidation status of the iron ion after absorption, 4) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 5) its identical excretion mechanisms.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Ferrous gluconate, CAS 299-29-6,
SMILES [Fe+2].O[C@H]([C@@H](O)C([O-])=O)[C@H](O)[C@H](O)CO.[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO,
MW 446.14 g/mol
The molecular formula is considered to be C12H22FeO14. It is used to replete and maintain the total body content of iron.
The purity, when specified, is given in terms of iron content, which is ca .11.7 % (11.58 % / 11.6 %/ 11.7 %)
Target Chemical: Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of Fe gluconate available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Ferrous gluconate or Iron(II) gluconate (source) and Sodium Iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - contain the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length. In case of ferrous gluconate two gluconic acid-chains (C6H11O7-) are involved and in case of iron glucoheptonate it is C7H10O8.
After oral intake of these substances the low pH in the upper GI tract will provoke dissociation releasing gluconic acid / glucoheptonic acid and ferrous and ferric iron, respectively. Therefore, at low pH values both substances are not able to participate in complexation of metal cations (Alekseev et al., 1998).
This dissociation has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998).
In the posterior parts of the GI tract, in the small intestines, where pH raises, new complexes can be formed, impacting any additional absorption of both substances again in a similar way. This however is not of great importance as the major absorption of iron takes place in the upper GI tract, where the pH values are low.
The released free gluconate or glucoheptonate anions, however, can further sequester luminal or mucosal metal affecting the absorption. The impact of this on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13.). Therefore, gluconate-metal complexes are used for food fortification. Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13.).
All this shows that the metal cation originated from the gluconate /glucoheptonate complexes is subjected to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Substantiating these facts, it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.Moreover, lactonisation occurs at low pH values (i.e. observed under pH 3.8 in case of Ca gluconate complexes) that would hinder complexation (Pallagi et al., 2010).
The ferric iron of sodium ferric glucoheptonate needs to be transformed into the soluble ferrous iron before being absorbed (Andrews, 2000). The reduction of ferric iron is aided by the acidic environment of the stomach and the proximal duodenum (enhancing in the first place solubility), dietary components like ascorbic acid and duodenal cytochrome b (Dcytb) catalysing duodenal ferric reductase activity (Atanasova, 2005). Thus the metal ion is expected to be absorbed similarly in both cases, despite the different origin oxidation status.
Generally, the extent of iron absorption depends on body needs and is highly regulated (EFSA, 2006; Candela et al., 1984). Subsequently, after absorption, the sugar residues, which differ by one methyl rest, will both be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to gluconate or glucoheptonate moiety up to considerable amounts.
Taken together, both substances are expected to have an identical toxicodynamic and toxicological behaviour, which is based on the fact that these similar structures are metabolised by the same pathways, leading to the same substances.
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Details on results:
- The group mean increases in bodyweight after 12 weeks are given in table 1. Analysis of the combined data showed that at the higher dose level all four compounds significantly depressed growth rate in the male rats, but not in the females. At the lower dose level the depressions produced in the males by the fumarate and the gluconate were not significant (P = 0.05). None of the organ weights ( expressed in mg/100 gr bodyweight) in the dosed groups differed significantly (P = 0.05) from those of the controls. Likewise no abnormalities were found in the red or total white cell counts or hemoglobin concentrations.
Apart from a slight and variable increase in iron deposition in the tissue phagocytes (e.g., Kupffer cells, pulmonary macrophages and adrenal cortical littoral cells), histologic examination of the organs listed above revealed no abnormalities that could be attributed to the drugs. - Dose descriptor:
- NOAEL
- Remarks:
- Fe Gluconate
- Effect level:
- 427.35 mg/kg bw/day (nominal)
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- body weight and weight gain
- haematology
- histopathology: non-neoplastic
- Remarks on result:
- other: calculated based on the ferrous iron content of 11.7 % given for ferrous gluconate
- Dose descriptor:
- NOAEL
- Remarks:
- Fe
- Effect level:
- 50 other: mg Fe/kg
- Based on:
- element
- Sex:
- male/female
- Basis for effect level:
- body weight and weight gain
- haematology
- histopathology: non-neoplastic
- Critical effects observed:
- no
- Conclusions:
- This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
- Executive summary:
The animal experiments were designed to compare the toxicologic and hematinic properties of ferrous fumarate with those of ferrous sulphate A.R.,ferrous succinate and ferrous gluconate B.P.C (Berenbaum, 1960). The ferrous iron contents of these four salts are 33.0, 20.0, 24.8 and 11.7 per cent, respectively. The sulphate was administered as an aqueous solution and the other three compounds as aqueous suspensions containing 0.1 per cent w/v of tragacanth.
The subchronic oral toxicities of the four ferrous salts were compared in albino rats of the WAG strain. Ferrous sulphate solution and suspensions of the fumarate, gluconate and succinate containing 20 rng Fe/mL were employed in this experiment. Forty-five male and 45 female rats (40 to 100 gr bodyweight) were randomly distributed into nine groups of five males and five females. One group was not dosed and served as controls, while the other eight groups received oral doses of one or other of the iron compounds at a level of 50 or 100 mg Fe/Kg. The animals were individually weighed at intervals and dosed daily, excluding weekends. After 12 weeks’ dosing, the red and total white cell counts and hemoglobin concentrations were determined on two males and two females from each group. All the rats were then killed, and the major organs (liver, spleen, heart, lungs, thymus, kidneys, adrenals, thyroid, testes, prostate, seminal vesicles, ovaries and uterus) were excised, blotted dry, and weighed. The organs from two males and two females from each group dosed at 50 mg Fe/Kg were examined histologically.
The group mean increases in bodyweight after 12 weeks are given in Table 1. Analysis of the combined data showed that at the higher dose level all four compounds significantly depressed growth rate in the male rats, but not in the females. At the lower dose level the depressions produced in the males by the fumarate and the gluconate were not significant (P = 0.05). None of the organ weights (expressed in mg/100 gr bodyweight) in the dosed groups differed significantly (P = 0.05) from those of the controls. Likewise no abnormalities were found in the red or total white cell counts or hemoglobin concentrations.
Apart from a slight and variable increase in iron deposition in the tissue phagocytes (e.g., Kupffer cells, pulmonary macrophages and adrenal cortical littoral cells), histologic examination of the organs listed above revealed no abnormalities that could be attributed to the drugs.
Taking into account all given data, a NOAEL of 50 mg Fe/kg bw, corresponding to a value of 427.35 mg Ferrous gluconate/kg bw can be established.
This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the source and the target substance and the expected identical behaviour in the human or animal body. This is based on the fact, that they both are metal complexes consisting of iron and sugar-like carbohydrates that are believed to share the same absorption, distribution and metabolic pathways.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity, 2) the same behaviour in the acidic environment in the stomach and proximal duodenum (dissociation), 3) the same oxidation status of the iron ion after absorption, 4) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 5) its identical excretion mechanisms.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Ferrous gluconate, CAS 299-29-6,
SMILES [Fe+2].O[C@H]([C@@H](O)C([O-])=O)[C@H](O)[C@H](O)CO.[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO,
MW 446.14 g/mol
The molecular formula is considered to be C12H22FeO14. It is used to replete and maintain the total body content of iron.
The purity, when specified, is given in terms of iron content, which is ca .11.7 % (11.58 % / 11.6 %/ 11.7 %)
Target Chemical: Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of Fe gluconate available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Ferrous gluconate or Iron(II) gluconate (source) and Sodium Iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - contain the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length. In case of ferrous gluconate two gluconic acid-chains (C6H11O7-) are involved and in case of iron glucoheptonate it is C7H10O8.
After oral intake of these substances the low pH in the upper GI tract will provoke dissociation releasing gluconic acid / glucoheptonic acid and ferrous and ferric iron, respectively. Therefore, at low pH values both substances are not able to participate in complexation of metal cations (Alekseev et al., 1998).
This dissociation has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998).
In the posterior parts of the GI tract, in the small intestines, where pH raises, new complexes can be formed, impacting any additional absorption of both substances again in a similar way. This however is not of great importance as the major absorption of iron takes place in the upper GI tract, where the pH values are low.
The released free gluconate or glucoheptonate anions, however, can further sequester luminal or mucosal metal affecting the absorption. The impact of this on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13.). Therefore gluconate-metal complexes are used for food fortification. Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13.).
All this shows that the metal cation originated from the gluconate /glucoheptonate complexes is subjected to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Substantiating these facts, it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.Moreover, lactonisation occurs at low pH values (i.e. observed under pH 3.8 in case of Ca gluconate complexes) that would hinder complexation (Pallagi et al., 2010).
The ferric iron of sodium ferric glucoheptonate needs to be transformed into the soluble ferrous iron before being absorbed (Andrews, 2000). The reduction of ferric iron is aided by the acidic environment of the stomach and the proximal duodenum (enhancing in the first place solubility), dietary components like ascorbic acid and duodenal cytochrome b (Dcytb) catalysing duodenal ferric reductase activity (Atanasova, 2005). Thus the metal ion is expected to be absorbed similarly in both cases, despite the different origin oxidation status.
Generally, the extent of iron absorption depends on body needs and is highly regulated (EFSA, 2006; Candela et al., 1984). Subsequently, after absorption, the sugar residues, which differ by one methyl rest, will both be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to gluconate or glucoheptonate moiety up to considerable amounts.
Taken together, both substances are expected to have an identical toxicodynamic and toxicological behaviour, which is based on the fact that these similar structures are metabolised by the same pathways, leading to the same substances.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Details on results:
- No serious body weight changes or mortality occurred among the cats receiving ferrous gluconate. Occasional vomiting and diarrhea occurred at the lower dosages with both compounds. The intensity of the emesis increased with increase of dosage and was associated with a decrease in the incidence of diarrhea. The emesis appeared to be entirely local in effect, since it occurred in less than an hour after medication. Other than the emesis, the cats appeared to suffer no ill effects from the medication. The appetite except at the highest dosages remained normal in every cat.
- Dose descriptor:
- NOAEL
- Remarks on result:
- not determinable
- Critical effects observed:
- no
- Conclusions:
- This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
- Executive summary:
The acute toxicity of ferrous gluconate (massive hypertherapeutic doses) was determined in direct comparison with that of ferrous sulfate following repeated oral administration in cats for 2 weeks (Hoppe, 1955). Daily doses of 25, 50, 100, 200 and 400 mg/kg of ferrous sulfate and 100, 200, 400, 800 and 1600 mg/kg of ferrous gluconate were administered as a powder by capsule to 2 cats at each dose level 5 days a week for 2 weeks.
All animals were housed in air-conditioned quarters with food and water available at all times, with the exception of the period immediately preceding the oral medications.
No serious body weight changes or mortality occurred among the cats receiving ferrous gluconate. Occasional vomiting and diarrhea occurred at the lower dosages. The intensity of the emesis increased with increase of dosage and was associated with a decrease in the incidence of diarrhea. The emesis appeared to be entirely local in effect, since it occurred in less than an hour after medication. Other than the emesis, the cats appeared to suffer no ill effects from the medication. The appetite except at the highest dosages remained normal in every cat.
The protective emesis due to local irritant effects is a safety factor which is evident from the oral studies in the cat and the dog. These data suggest prompt, gentle gastric lavage along with supportive therapy for shock as an effective emergency measure in those cases where, for any reason, vomiting does not occur spontaneously following oral ingestion of ferrus sulfate, ferrous gluconate or other soluble iron salts.
This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the source and the target substance and the expected identical behaviour in the human or animal body. This is based on the fact, that they both are metal complexes consisting of iron and sugar-like carbohydrates that are believed to share the same absorption, distribution and metabolic pathways.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity, 2) the same behaviour in the acidic environment in the stomach and proximal duodenum (dissociation), 3) the same oxidation status of the iron ion after absorption, 4) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 5) its identical excretion mechanisms.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Ferrous gluconate, CAS 299-29-6,
SMILES [Fe+2].O[C@H]([C@@H](O)C([O-])=O)[C@H](O)[C@H](O)CO.[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO,
MW 446.14 g/mol
The molecular formula is considered to be C12H22FeO14. It is used to replete and maintain the total body content of iron.
The purity, when specified, is given in terms of iron content, which is ca .11.7 % (11.58 % / 11.6 %/ 11.7 %)
Target Chemical: Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of Fe gluconate available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Ferrous gluconate or Iron(II) gluconate (source) and Sodium Iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - contain the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length. In case of ferrous gluconate two gluconic acid-chains (C6H11O7-) are involved and in case of iron glucoheptonate it is C7H10O8.
After oral intake of these substances the low pH in the upper GI tract will provoke dissociation releasing gluconic acid / glucoheptonic acid and ferrous and ferric iron, respectively. Therefore, at low pH values both substances are not able to participate in complexation of metal cations (Alekseev et al., 1998).
This dissociation has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998).
In the posterior parts of the GI tract, in the small intestines, where pH raises, new complexes can be formed, impacting any additional absorption of both substances again in a similar way. This however is not of great importance as the major absorption of iron takes place in the upper GI tract, where the pH values are low.
The released free gluconate or glucoheptonate anions, however, can further sequester luminal or mucosal metal affecting the absorption. The impact of this on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13.). Therefore gluconate-metal complexes are used for food fortification. Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13.).
All this shows that the metal cation originated from the gluconate /glucoheptonate complexes is subjected to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Substantiating these facts, it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.Moreover, lactonisation occurs at low pH values (i.e. observed under pH 3.8 in case of Ca gluconate complexes) that would hinder complexation (Pallagi et al., 2010).
The ferric iron of sodium ferric glucoheptonate needs to be transformed into the soluble ferrous iron before being absorbed (Andrews, 2000). The reduction of ferric iron is aided by the acidic environment of the stomach and the proximal duodenum (enhancing in the first place solubility), dietary components like ascorbic acid and duodenal cytochrome b (Dcytb) catalysing duodenal ferric reductase activity (Atanasova, 2005). Thus the metal ion is expected to be absorbed similarly in both cases, despite the different origin oxidation status.
Generally, the extent of iron absorption depends on body needs and is highly regulated (EFSA, 2006; Candela et al., 1984). Subsequently, after absorption, the sugar residues, which differ by one methyl rest, will both be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to gluconate or glucoheptonate moiety up to considerable amounts.
Taken together, both substances are expected to have an identical toxicodynamic and toxicological behaviour, which is based on the fact that these similar structures are metabolised by the same pathways, leading to the same substances.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Dose descriptor:
- NOAEL
- Remarks:
- Fe Gluconate
- Effect level:
- 61 mg/kg diet
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- food consumption and compound intake
- food efficiency
- haematology
- organ weights and organ / body weight ratios
- Critical effects observed:
- no
- Conclusions:
- This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic ater repeated oral exposure according to 1272/2008/EC.
- Executive summary:
Fortifying food with iron has been widely studied as a strategy to prevent iron deficiency anaemia (Navas-Carretero, 2006). This work comparatively assessed the bioavailability of two forms of iron, ferrous gluconate or ferric pyrophosphate encapsulated in liposomes (lipofer®), when used as fortificants in meat pate. Ferrous gluconate, sulphate and lactate belong to the group of freely water soluble iron compounds. Thanks to being highly soluble in water, they enter the common pool on non-heme iron completely upon digestion and present high bioavailability. Three groups of growing rats consumed during 28 days either a control diet (AIN-93G), or two diets prepared with enriched pate as the unique source of iron and fat. Body weight and diet intake were measured weekly, and during the last week faeces were collected. On day 28 animals were sacrificed, livers and spleens were removed and stored. Haemoglobin and total iron binding capacity (TIBC) were determined.
There were not significant differences among the three groups in body weight and apparent iron absorption, although food intake in the two pate groups was significantly higher compared to the control group. There were no differences in liver and spleen iron content and concentration, neither in haemoglobin and TIBC values. These results indicated that iron bioavailability of pate enriched with ferrous gluconate or ferric pyrophosphate encapsulated in liposomes was similar, and thus both sources of iron are good candidates to be used as fortifiers in meat based products. The present results support that encapsulation of ferric pyrophosphate, as in Lipofer®, protects iron from forming non-absorbable compounds and improves iron bioavailability. The present outcome needs to be validated in humans.
This result is also relevant for iron glucoheptonate, as ferrous gluconate is highly similar to iron glucoheptonate, which is therefore considered to be also not toxic after repeated oral exposure according to 1272/2008/EC.
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the organic part of the source and the target substance and their expected identical behaviour in the human or animal body.
The target substance – as one member in the group of the chelate complexes - is known to dissociate in the upper GI tract at low pH values into the metal ion and the glucoheptonic acid anion.
The read-across substances gluconic acid, glucono-delta-lactone, sodium gluconate, potassium gluconate and calcium gluconate similarly release gluconate anions which are as well sugar-like compounds and are metabolised by the same metabolic pathways as glucoheptonate anion, and are indeed intermediate metabolites, which are partly build when the glucoheptonate anion is broken down.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity and 2) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 3) their identical excretion mechanisms.
Therefore, by using the toxicity profile of gluconic acid, glucono-delta-lactone, sodium, potassium and calcium gluconate, the absence of toxicity of the organic moiety of the target molecule - glucoheptonate anion - can be confirmed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Gluconates and derivatives
D-Gluconic acid, CAS 526-95-4;
SMILES: O=C(O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 196.16 g/mol
The molecular formula is C6H12O7
Purity (%) of Gluconic acid 50% solution: 49-52% (OECD SIDS, 2004)
Glucono-delta-lactone CAS 90-80-2
SMILES: C([C@@H]1[C@H]([C@@H]([C@H](C(=O)O1)O)O)O)O
MW 178.14 g/mol
The molecular formula is C6H10O6
Purity (%) of Glucono-delta-lactone: 99-101% (OECD SIDS, 2004)
Sodium D-gluconate CAS 527-07-1
SMILES: [Na+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 218.14 g/mol
The molecular formula is C6H11NaO7
Purity (%) of Sodium gluconate: 98-102% (OECD SIDS, 2004)
Calcium D-gluconate CAS-299-28-5; CAS 18016-24-5
SMILES: [Ca+2].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO.[O-C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 430.373 g/mol
The molecular formula is C12H22CaO14
Purity (%) of Calcium gluconate: 98-104% (OECD SIDS, 2004)
Potassium D-gluconate CAS 299-27-4)
SMILES: [K+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 234.246 g/mol
The molecular formula is C6H11KO7
Purity (%) of Potassium gluconate: 97-103% (OECD SIDS, 2004)
Gluconic acid and its derivatives glucono-delta-lactone, sodium gluconate, calcium gluconate and potassium gluconate and sodium iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - are built of the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length (gluconic acid-chains (C6H11O7-) and glucoheptonate C7H10O8).
Target Chemical:
Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of gluconic acid and its derivatives available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Gluconates and their derivatives all belong to the aldonic acids (Escandar et al., 1992; Frutos et al., 1998) because they are derivatives of aldoses, sugars that contain one aldehyde group, which is oxidised to carboxylic group (Berg et al., 2007). They form lactone form, a ring structure the same as in the sugar’s cyclic hemiacetal form (Berg et al., 2007).
The dissociation of metal gluconate and glucoheptonate complexes at low pH values in the upper GI tract has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998). Consequently, the metal ion and the gluconic or glucoheptonic acid anion will be subject to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Considering this dissociation, the information that it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body is a very useful information. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.
The released free gluconate or glucoheptonate anions, however, can in the posterior parts of the GI tract – in the small intestines, where pH raises - further sequester luminal or mucosal metal affecting the absorption. The impact of the released free gluconate or glucoheptonate anions on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13). Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13).
After absorption, the above mentioned sugar residues, will all be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to the gluconate or glucoheptonate moiety up to considerable amounts.
In conclusion, gluconate and glucoheptonate anions form complexes with metals of the same geometry and stoichiometry. The same functional groups of the ligand are involved in the formation of coordinative bonds. Identical behaviour of gluconates and glucoheptonates depending on pH, molar concentration of metal: ligand components and physical state is verified by analytical methods. Based on the structural similarity of gluconates and glucoheptonates, their functional groups, composition, toxicodynamic, toxicokinetic, and toxicological behaviour, one can expect a very similar behaviour of these substances in living organisms.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Description (incidence and severity):
- No death or clinical signs of abnormality were observed in any of the groups.
- Mortality:
- no mortality observed
- Description (incidence):
- No death or clinical signs of abnormality were observed in any of the groups.
- Body weight and weight changes:
- not specified
- Food consumption and compound intake (if feeding study):
- not examined
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- no effects observed
- Ophthalmological findings:
- not examined
- Haematological findings:
- not specified
- Clinical biochemistry findings:
- not specified
- Urinalysis findings:
- not specified
- Behaviour (functional findings):
- not specified
- Immunological findings:
- not specified
- Organ weight findings including organ / body weight ratios:
- not specified
- Gross pathological findings:
- not specified
- Neuropathological findings:
- not specified
- Histopathological findings: non-neoplastic:
- effects observed, non-treatment-related
- Description (incidence and severity):
- Histopathological examination showed a thickening of the limiting ridge of the stomach in 5 out of 12 males at 2000 mg/kg bw per day dose. No toxic changes associated with the test article were detected. As the limiting ridge is a tissue specific to rodents, this lesion is not toxicologically relevant for humans. Other lesions occurred incidentally and were not treatment-related.
- Histopathological findings: neoplastic:
- not specified
- Other effects:
- not specified
- Dose descriptor:
- NOAEL
- Remarks:
- Na Gluconate
- Effect level:
- 1 000 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male
- Basis for effect level:
- clinical signs
- histopathology: non-neoplastic
- mortality
- Dose descriptor:
- NOAEL
- Remarks:
- Na Gluconate
- Effect level:
- 2 000 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- female
- Basis for effect level:
- clinical signs
- histopathology: non-neoplastic
- mortality
- Critical effects observed:
- no
- Conclusions:
- None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. The NOAEL of sodium gluconate determined from the 28 days studies on rats was equal to 1000 mg/kg bw for males and 2000 mg/kg bw for females. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
This result is also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important. - Executive summary:
A 28-day study was conducted by feeding rats by gavage with sodium gluconate at doses of 0, 500, 1000, 2000 mg/kg bw in water at a volume of 1 mL/ 100g bw. No death or clinical signs of abnormality were observed in any of the groups. Histopathological examination showed a thickening of the limiting ridge of the stomach in 5 out of 12 males at 2000 mg/kg bw per day dose. No toxic changes associated with the test article were detected. As the limiting ridge is a tissue specific to rodents, this lesion is not toxicologically relevant for humans. Other lesions occurred incidentally and were not treatment -related. The NOAEL was estimated to be 1000 mg/kg bw/day for males and 2000 mg/kg bw/day for female (Mochizuki, M, Bozo Research Center, 1995a).
This result is also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important.
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the organic part of the source and the target substance and their expected identical behaviour in the human or animal body.
The target substance – as one member in the group of the chelate complexes - is known to dissociate in the upper GI tract at low pH values into the metal ion and the glucoheptonic acid anion.
The read-across substances gluconic acid, glucono-delta-lactone, sodium gluconate, potassium gluconate and calcium gluconate similarly release gluconate anions which are as well sugar-like compounds and are metabolised by the same metabolic pathways as glucoheptonate anion, and are indeed intermediate metabolites, which are partly build when the glucoheptonate anion is broken down.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity and 2) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 3) their identical excretion mechanisms.
Therefore, by using the toxicity profile of gluconic acid, glucono-delta-lactone, sodium, potassium and calcium gluconate, the absence of toxicity of the organic moiety of the target molecule - glucoheptonate anion - can be confirmed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Gluconates and derivatives
D-Gluconic acid, CAS 526-95-4;
SMILES: O=C(O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 196.16 g/mol
The molecular formula is C6H12O7
Purity (%) of Gluconic acid 50% solution: 49-52% (OECD SIDS, 2004)
Glucono-delta-lactone CAS 90-80-2
SMILES: C([C@@H]1[C@H]([C@@H]([C@H](C(=O)O1)O)O)O)O
MW 178.14 g/mol
The molecular formula is C6H10O6
Purity (%) of Glucono-delta-lactone: 99-101% (OECD SIDS, 2004)
Sodium D-gluconate CAS 527-07-1
SMILES: [Na+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 218.14 g/mol
The molecular formula is C6H11NaO7
Purity (%) of Sodium gluconate: 98-102% (OECD SIDS, 2004)
Calcium D-gluconate CAS-299-28-5; CAS 18016-24-5
SMILES: [Ca+2].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO.[O-C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 430.373 g/mol
The molecular formula is C12H22CaO14
Purity (%) of Calcium gluconate: 98-104% (OECD SIDS, 2004)
Potassium D-gluconate CAS 299-27-4)
SMILES: [K+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 234.246 g/mol
The molecular formula is C6H11KO7
Purity (%) of Potassium gluconate: 97-103% (OECD SIDS, 2004)
Gluconic acid and its derivatives glucono-delta-lactone, sodium gluconate, calcium gluconate and potassium gluconate and sodium iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - are built of the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length (gluconic acid-chains (C6H11O7-) and glucoheptonate C7H10O8).
Target Chemical:
Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of gluconic acid and its derivatives available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Gluconates and their derivatives all belong to the aldonic acids (Escandar et al., 1992; Frutos et al., 1998) because they are derivatives of aldoses, sugars that contain one aldehyde group, which is oxidised to carboxylic group (Berg et al., 2007). They form lactone form, a ring structure the same as in the sugar’s cyclic hemiacetal form (Berg et al., 2007).
The dissociation of metal gluconate and glucoheptonate complexes at low pH values in the upper GI tract has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998). Consequently, the metal ion and the gluconic or glucoheptonic acid anion will be subject to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Considering this dissociation, the information that it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body is a very useful information. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.
The released free gluconate or glucoheptonate anions, however, can in the posterior parts of the GI tract – in the small intestines, where pH raises - further sequester luminal or mucosal metal affecting the absorption. The impact of the released free gluconate or glucoheptonate anions on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13). Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13).
After absorption, the above mentioned sugar residues, will all be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to the gluconate or glucoheptonate moiety up to considerable amounts.
In conclusion, gluconate and glucoheptonate anions form complexes with metals of the same geometry and stoichiometry. The same functional groups of the ligand are involved in the formation of coordinative bonds. Identical behaviour of gluconates and glucoheptonates depending on pH, molar concentration of metal: ligand components and physical state is verified by analytical methods. Based on the structural similarity of gluconates and glucoheptonates, their functional groups, composition, toxicodynamic, toxicokinetic, and toxicological behaviour, one can expect a very similar behaviour of these substances in living organisms.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Description (incidence and severity):
- No revisions in the general condition were observed in the animals over the study period.
- Mortality:
- no mortality observed
- Description (incidence):
- No deaths occurred during the study period.
- Body weight and weight changes:
- no effects observed
- Description (incidence and severity):
- No revisions in the body weight were observed in the animals over the study period.
- Food consumption and compound intake (if feeding study):
- no effects observed
- Description (incidence and severity):
- No revisions in the food intake were observed in the animals over the study period.
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- no effects observed
- Description (incidence and severity):
- No revisions in the water intake were observed in the animals over the study period.
- Ophthalmological findings:
- no effects observed
- Description (incidence and severity):
- No changes were observed in the investigated ophthalmologic tests
- Haematological findings:
- no effects observed
- Description (incidence and severity):
- No changes were observed in the investigated hematology
- Clinical biochemistry findings:
- not specified
- Description (incidence and severity):
- No changes were observed in the investigated blood chemistry
- Urinalysis findings:
- effects observed, treatment-related
- Description (incidence and severity):
- Statistically significant differences in some urinary parameters reported in animals receiving 2.5 or 5% sodium gluconate were comparable to those observed in the NaCl control group, and were interpreted as related to the high sodium concentration of the diet.
- Behaviour (functional findings):
- not specified
- Immunological findings:
- not specified
- Organ weight findings including organ / body weight ratios:
- not specified
- Gross pathological findings:
- not specified
- Neuropathological findings:
- not specified
- Histopathological findings: non-neoplastic:
- no effects observed
- Description (incidence and severity):
- Histopathological examination indicated no adverse effects as a result of the treatment regime
- Histopathological findings: neoplastic:
- not specified
- Other effects:
- not specified
- Details on results:
- No deaths occurred during the study period. No revisions in the general condition, body weight, or food and water intake were observed in the animals over the study period. No changes were observed in the investigated ophthalmologic tests, urinalysis, hematology and blood chemistry over the study period. In addition, histopathological examination indicated no adverse effects as a result of the treatment regime. Statistically significant differences in some urinary parameters reported in animals receiving 2.5 or 5% sodium gluconate were comparable to those observed in the NaCl control group, and were interpreted as related to the high sodium concentration of the diet.
- Dose descriptor:
- NOAEL
- Remarks:
- Na gluconate
- Effect level:
- 4 100 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male
- Basis for effect level:
- body weight and weight gain
- clinical signs
- gross pathology
- histopathology: non-neoplastic
- mortality
- ophthalmological examination
- organ weights and organ / body weight ratios
- urinalysis
- water consumption and compound intake
- Remarks on result:
- other: 5% w/w sodium gluconate (max. 4100 mg/kg bw for males and 4400 mg/kg bw for females)
- Dose descriptor:
- NOAEL
- Remarks:
- Na gluconate
- Effect level:
- 4 400 mg/kg bw/day (nominal)
- Based on:
- test mat.
- Sex:
- female
- Basis for effect level:
- body weight and weight gain
- clinical signs
- gross pathology
- histopathology: non-neoplastic
- mortality
- ophthalmological examination
- organ weights and organ / body weight ratios
- urinalysis
- water consumption and compound intake
- Remarks on result:
- other: 5% w/w sodium gluconate (max. 4100 mg/kg bw for males and 4400 mg/kg bw for females)
- Critical effects observed:
- no
- Conclusions:
- None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important. - Executive summary:
Another 28-day toxicity study in rats fed with a diet containing up to 5% w/w sodium gluconate (max. 4100 mg/kg bw for males and 4400 mg/kg bw for females) was conducted using a control group receiving equivalent concentration of sodium in the form of NaCl in order to differentiate the potential effects of high doses of sodium intake. No deaths occurred during the study period. No revisions in the general condition, body weight, or food and water intake were observed in the animals over the study period. No changes were observed in the investigated ophthalmologic tests, urinalysis, hematology and blood chemistry over the study period. In addition, histopathological examination indicated no adverse effects as a result of the treatment regime. Statistically significant differences in some urinary parameters reported in animals receiving 2.5 or 5% sodium gluconate were comparable to those observed in the NaCl control group, and were interpreted as related to the high sodium concentration of the diet.
The authors concluded that the NOAEL was 5% (equal to 4100 mg/kg bw per day). However, the JECFA committee who evaluated this report has concluded that the study was not suitable for identifying a NOAEL because of the small group sizes and the positive findings in the qualitative analysis, even if they have acknowledged that the effects shown in the qualitative urine analyses were related to the high sodium intake (Mochizuki, M. Bozo Research Center, 1997). Nonetheless, this study demonstrates the lack of effects of the gluconate anion even in large doses as the urinary effects were attributed to the high sodium intake and was therefore considered as critical for this endpoint.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important.
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the organic part of the source and the target substance and their expected identical behaviour in the human or animal body.
The target substance – as one member in the group of the chelate complexes - is known to dissociate in the upper GI tract at low pH values into the metal ion and the glucoheptonic acid anion.
The read-across substances gluconic acid, glucono-delta-lactone, sodium gluconate, potassium gluconate and calcium gluconate similarly release gluconate anions which are as well sugar-like compounds and are metabolised by the same metabolic pathways as glucoheptonate anion, and are indeed intermediate metabolites, which are partly build when the glucoheptonate anion is broken down.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity and 2) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 3) their identical excretion mechanisms.
Therefore, by using the toxicity profile of gluconic acid, glucono-delta-lactone, sodium, potassium and calcium gluconate, the absence of toxicity of the organic moiety of the target molecule - glucoheptonate anion - can be confirmed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Gluconates and derivatives
D-Gluconic acid, CAS 526-95-4;
SMILES: O=C(O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 196.16 g/mol
The molecular formula is C6H12O7
Purity (%) of Gluconic acid 50% solution: 49-52% (OECD SIDS, 2004)
Glucono-delta-lactone CAS 90-80-2
SMILES: C([C@@H]1[C@H]([C@@H]([C@H](C(=O)O1)O)O)O)O
MW 178.14 g/mol
The molecular formula is C6H10O6
Purity (%) of Glucono-delta-lactone: 99-101% (OECD SIDS, 2004)
Sodium D-gluconate CAS 527-07-1
SMILES: [Na+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 218.14 g/mol
The molecular formula is C6H11NaO7
Purity (%) of Sodium gluconate: 98-102% (OECD SIDS, 2004)
Calcium D-gluconate CAS-299-28-5; CAS 18016-24-5
SMILES: [Ca+2].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO.[O-C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 430.373 g/mol
The molecular formula is C12H22CaO14
Purity (%) of Calcium gluconate: 98-104% (OECD SIDS, 2004)
Potassium D-gluconate CAS 299-27-4)
SMILES: [K+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 234.246 g/mol
The molecular formula is C6H11KO7
Purity (%) of Potassium gluconate: 97-103% (OECD SIDS, 2004)
Gluconic acid and its derivatives glucono-delta-lactone, sodium gluconate, calcium gluconate and potassium gluconate and sodium iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - are built of the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length (gluconic acid-chains (C6H11O7-) and glucoheptonate C7H10O8).
Target Chemical:
Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of gluconic acid and its derivatives available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Gluconates and their derivatives all belong to the aldonic acids (Escandar et al., 1992; Frutos et al., 1998) because they are derivatives of aldoses, sugars that contain one aldehyde group, which is oxidised to carboxylic group (Berg et al., 2007). They form lactone form, a ring structure the same as in the sugar’s cyclic hemiacetal form (Berg et al., 2007).
The dissociation of metal gluconate and glucoheptonate complexes at low pH values in the upper GI tract has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998). Consequently, the metal ion and the gluconic or glucoheptonic acid anion will be subject to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Considering this dissociation, the information that it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body is a very useful information. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.
The released free gluconate or glucoheptonate anions, however, can in the posterior parts of the GI tract – in the small intestines, where pH raises - further sequester luminal or mucosal metal affecting the absorption. The impact of the released free gluconate or glucoheptonate anions on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13). Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13).
After absorption, the above mentioned sugar residues, will all be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to the gluconate or glucoheptonate moiety up to considerable amounts.
In conclusion, gluconate and glucoheptonate anions form complexes with metals of the same geometry and stoichiometry. The same functional groups of the ligand are involved in the formation of coordinative bonds. Identical behaviour of gluconates and glucoheptonates depending on pH, molar concentration of metal: ligand components and physical state is verified by analytical methods. Based on the structural similarity of gluconates and glucoheptonates, their functional groups, composition, toxicodynamic, toxicokinetic, and toxicological behaviour, one can expect a very similar behaviour of these substances in living organisms.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Description (incidence and severity):
- Increased frequency of vomiting and loose or watery stools were observed in the 1000 and 2000 mg/kg bw dose groups, as compared to controls.
- Mortality:
- no mortality observed
- Description (incidence):
- None of the animals died during the period of treatment in any dose group
- Body weight and weight changes:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the body weight
- Food consumption and compound intake (if feeding study):
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the food intake
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the water intake
- Ophthalmological findings:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the ophthalmologic test
- Haematological findings:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the haematological test
- Clinical biochemistry findings:
- not specified
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the blood chemistry analysis
- Urinalysis findings:
- effects observed, treatment-related
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the urinalysis
- Behaviour (functional findings):
- not specified
- Immunological findings:
- not specified
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the organ weight examination.
- Gross pathological findings:
- not specified
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the autopsy examination.
- Neuropathological findings:
- not specified
- Histopathological findings: non-neoplastic:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in histopathological examination.
- Histopathological findings: neoplastic:
- not specified
- Other effects:
- no effects observed
- Description (incidence and severity):
- No significantly toxicologically changes were detected in the electrocardiography examination.
- Details on results:
- Repeated toxicity studies were also performed on Beagle dogs with sodium gluconate administered orally for 4 weeks at 500, 1000, 2000 mg/kg bw. doses. None of the animals died during the period of treatment in any dose group and no significantly toxicologically changes were detected in the body weight, food intake, water intake, urinalysis, haematological test, blood chemistry analysis, ophthalmologic test, electrocardiography, autopsy and organ weight or in histopathological examination. However, increased frequency of vomiting and loose or watery stools were observed in the 1000 and 2000 mg/kg bw. dose groups, as compared to controls.
- Dose descriptor:
- NOAEL
- Remarks:
- Na gluconate
- Effect level:
- 500 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- body weight and weight gain
- clinical biochemistry
- clinical signs
- food consumption and compound intake
- histopathology: non-neoplastic
- mortality
- ophthalmological examination
- urinalysis
- water consumption and compound intake
- Critical effects observed:
- no
- Conclusions:
- None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important. - Executive summary:
Repeated toxicity studies were also performed on Beagle dogs with sodium gluconate administered orally for 4 weeks at 500, 1000, 2000 mg/kg bw doses. None of the animals died during the period of treatment in any dose group and no significantly toxicologically changes were detected in the body weight, food intake, water intake, urinalysis, haematological test, blood chemistry analysis, ophthalmologic test, electrocardiography, autopsy and organ weight or in histopathological examination. However, increased frequency of vomiting and loose or watery stools were observed in the 1000 and 2000 mg/kg bw dose groups, as compared to controls.
On the basis of these results, the non-toxic dose was estimated to be 500 mg/kg bw / day. However, the toxicological effects observed (vomiting, passage of loose or watery stools) were considered extremely slight since other tests did not show the same changes (Okamoto, M. Bozo Research Center, 1995a).
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that sodium gluconate is not toxic after repeated oral intake is important.
- Endpoint:
- sub-chronic toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the organic part of the source and the target substance and their expected identical behaviour in the human or animal body.
The target substance – as one member in the group of the chelate complexes - is known to dissociate in the upper GI tract at low pH values into the metal ion and the glucoheptonic acid anion.
The read-across substances gluconic acid, glucono-delta-lactone, sodium gluconate, potassium gluconate and calcium gluconate similarly release gluconate anions which are as well sugar-like compounds and are metabolised by the same metabolic pathways as glucoheptonate anion, and are indeed intermediate metabolites, which are partly build when the glucoheptonate anion is broken down.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity and 2) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 3) their identical excretion mechanisms.
Therefore, by using the toxicity profile of gluconic acid, glucono-delta-lactone, sodium, potassium and calcium gluconate, the absence of toxicity of the organic moiety of the target molecule - glucoheptonate anion - can be confirmed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Gluconates and derivatives
D-Gluconic acid, CAS 526-95-4;
SMILES: O=C(O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 196.16 g/mol
The molecular formula is C6H12O7
Purity (%) of Gluconic acid 50% solution: 49-52% (OECD SIDS, 2004)
Glucono-delta-lactone CAS 90-80-2
SMILES: C([C@@H]1[C@H]([C@@H]([C@H](C(=O)O1)O)O)O)O
MW 178.14 g/mol
The molecular formula is C6H10O6
Purity (%) of Glucono-delta-lactone: 99-101% (OECD SIDS, 2004)
Sodium D-gluconate CAS 527-07-1
SMILES: [Na+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 218.14 g/mol
The molecular formula is C6H11NaO7
Purity (%) of Sodium gluconate: 98-102% (OECD SIDS, 2004)
Calcium D-gluconate CAS-299-28-5; CAS 18016-24-5
SMILES: [Ca+2].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO.[O-C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 430.373 g/mol
The molecular formula is C12H22CaO14
Purity (%) of Calcium gluconate: 98-104% (OECD SIDS, 2004)
Potassium D-gluconate CAS 299-27-4)
SMILES: [K+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 234.246 g/mol
The molecular formula is C6H11KO7
Purity (%) of Potassium gluconate: 97-103% (OECD SIDS, 2004)
Gluconic acid and its derivatives glucono-delta-lactone, sodium gluconate, calcium gluconate and potassium gluconate and sodium iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - are built of the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length (gluconic acid-chains (C6H11O7-) and glucoheptonate C7H10O8).
Target Chemical:
Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of gluconic acid and its derivatives available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Gluconates and their derivatives all belong to the aldonic acids (Escandar et al., 1992; Frutos et al., 1998) because they are derivatives of aldoses, sugars that contain one aldehyde group, which is oxidised to carboxylic group (Berg et al., 2007). They form lactone form, a ring structure the same as in the sugar’s cyclic hemiacetal form (Berg et al., 2007).
The dissociation of metal gluconate and glucoheptonate complexes at low pH values in the upper GI tract has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998). Consequently, the metal ion and the gluconic or glucoheptonic acid anion will be subject to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Considering this dissociation, the information that it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body is a very useful information. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.
The released free gluconate or glucoheptonate anions, however, can in the posterior parts of the GI tract – in the small intestines, where pH raises - further sequester luminal or mucosal metal affecting the absorption. The impact of the released free gluconate or glucoheptonate anions on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13). Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13).
After absorption, the above mentioned sugar residues, will all be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to the gluconate or glucoheptonate moiety up to considerable amounts.
In conclusion, gluconate and glucoheptonate anions form complexes with metals of the same geometry and stoichiometry. The same functional groups of the ligand are involved in the formation of coordinative bonds. Identical behaviour of gluconates and glucoheptonates depending on pH, molar concentration of metal: ligand components and physical state is verified by analytical methods. Based on the structural similarity of gluconates and glucoheptonates, their functional groups, composition, toxicodynamic, toxicokinetic, and toxicological behaviour, one can expect a very similar behaviour of these substances in living organisms.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Description (incidence and severity):
- No deaths or other abnormalities were detected
- Mortality:
- no mortality observed
- Description (incidence):
- No deaths or other abnormalities were detected
- Body weight and weight changes:
- not specified
- Food consumption and compound intake (if feeding study):
- not examined
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- not specified
- Ophthalmological findings:
- not specified
- Haematological findings:
- not specified
- Clinical biochemistry findings:
- not specified
- Urinalysis findings:
- not specified
- Behaviour (functional findings):
- not specified
- Immunological findings:
- not specified
- Organ weight findings including organ / body weight ratios:
- not specified
- Gross pathological findings:
- not specified
- Neuropathological findings:
- not specified
- Histopathological findings: non-neoplastic:
- effects observed, non-treatment-related
- Description (incidence and severity):
- In all dose groups, thickening of the stratified squamous epithelium was detected at the anterior stomach, particularly the transitional area continuous with the pyloric stomach; the frequency and severity of this thickening increased with the dose. In high dose groups, submucosal inflammatory cell infiltration was also detected, but this change was not statistically significant.
- Histopathological findings: neoplastic:
- not specified
- Other effects:
- not specified
- Details on results:
- In all dose groups, thickening of the stratified squamous epithelium was detected at the anterior stomach, particularly the transitional area continuous with the pyloric stomach; the frequency and severity of this thickening increased with the dose. In high dose groups, submucosal inflammatory cell infiltration was also detected, but this change was not statistically significant. No deaths or other abnormalities were detected (Fukuhara K, 1978).
- Dose descriptor:
- NOAEL
- Remarks on result:
- not determinable due to absence of adverse toxic effects
- Critical effects observed:
- no
- Conclusions:
- None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. The NOAEL of sodium gluconate determined from the 28 days studies on rats was equal to 1000 mg/kg bw for males and 2000 mg/kg bw for females. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that glucono-delta-lactone is not toxic after repeated oral intake is important. - Executive summary:
Glucono-delta-lactone (250, 500, 1000, 2000 and 4000 mg/kgbw. for 6 months) was orally administered to Sprague-Dawley rats. In all dose groups, thickening of the stratified squamous epithelium was detected at the anterior stomach, particularly the transitional area continuous with the pyloric stomach; the frequency and severity of this thickening increased with the dose. In high dose groups, submucosal inflammatory cell infiltration was also detected, but this change was not statistically significant. No deaths or other abnormalities were detected (Fukuhara K, 1978). In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug : 1240-1350 mg/kgbw in 2.5% GDL group and 4920-5760 mg/kgbw in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that glucono-delta-lactone is not toxic after repeated oral intake is important.
- Endpoint:
- chronic toxicity: oral
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
An extended read-across statement is attached under section 13.
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The rationale for the analogue approach is the high structural similarity between the organic part of the source and the target substance and their expected identical behaviour in the human or animal body.
The target substance – as one member in the group of the chelate complexes - is known to dissociate in the upper GI tract at low pH values into the metal ion and the glucoheptonic acid anion.
The read-across substances gluconic acid, glucono-delta-lactone, sodium gluconate, potassium gluconate and calcium gluconate similarly release gluconate anions which are as well sugar-like compounds and are metabolised by the same metabolic pathways as glucoheptonate anion, and are indeed intermediate metabolites, which are partly build when the glucoheptonate anion is broken down.
In respect to oral repeated dose toxicity the source and the target substances are expected to bear the same toxicity potential based on their 1) structural similarity and 2) the same metabolic fate of gluconic acid and glucoheptonic acid and finally 3) their identical excretion mechanisms.
Therefore, by using the toxicity profile of gluconic acid, glucono-delta-lactone, sodium, potassium and calcium gluconate, the absence of toxicity of the organic moiety of the target molecule - glucoheptonate anion - can be confirmed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source Chemical: Gluconates and derivatives
D-Gluconic acid, CAS 526-95-4;
SMILES: O=C(O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 196.16 g/mol
The molecular formula is C6H12O7
Purity (%) of Gluconic acid 50% solution: 49-52% (OECD SIDS, 2004)
Glucono-delta-lactone CAS 90-80-2
SMILES: C([C@@H]1[C@H]([C@@H]([C@H](C(=O)O1)O)O)O)O
MW 178.14 g/mol
The molecular formula is C6H10O6
Purity (%) of Glucono-delta-lactone: 99-101% (OECD SIDS, 2004)
Sodium D-gluconate CAS 527-07-1
SMILES: [Na+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 218.14 g/mol
The molecular formula is C6H11NaO7
Purity (%) of Sodium gluconate: 98-102% (OECD SIDS, 2004)
Calcium D-gluconate CAS-299-28-5; CAS 18016-24-5
SMILES: [Ca+2].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO.[O-C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 430.373 g/mol
The molecular formula is C12H22CaO14
Purity (%) of Calcium gluconate: 98-104% (OECD SIDS, 2004)
Potassium D-gluconate CAS 299-27-4)
SMILES: [K+].[O-]C(=O)[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO
MW 234.246 g/mol
The molecular formula is C6H11KO7
Purity (%) of Potassium gluconate: 97-103% (OECD SIDS, 2004)
Gluconic acid and its derivatives glucono-delta-lactone, sodium gluconate, calcium gluconate and potassium gluconate and sodium iron glucoheptonate complex (HGA:Fe-1:1) (target) are structurally very similar. Both - the source and the target substance - are built of the same types of hydrocarbon constituents (sugar residues), which are only variable in carbon chain length (gluconic acid-chains (C6H11O7-) and glucoheptonate C7H10O8).
Target Chemical:
Sodium Iron glucoheptonate complex (HGA:Fe-1:1), CAS 1821694-04-5,
SMILES [Na+].[H]C([H])(O)C([H])(O)C1([H])O[Fe]2OC([H])(C([O-])=O)C([H])(O2)C1([H])O,
MW 354.8 g/mol (trihydrated from) or 300.8g/mol (anhydrous form)
The molecular formula is C7FeH10NaO8 *3H2O (trihydrated form).
No data on impurities of gluconic acid and its derivatives available. Information on purity of the registered substance is provided in the target record under "Test material" as confidential. The calculation of a hazard value for iron glucoheptonate is based on 76 % content of iron glucoheptonate in the registered product. Other components are ammonium sulfate and sodium sulfate. Ammonium sulfate and sodium sulfate are considered not to impact the repeated dose toxicity of the target substance to a significant degree, since ammonium sulfate is of relatively low toxicity. The NOAEL after feeding diets containing ammonium sulfate for 13 weeks to rats was 886 mg/kg bw/day. The only toxicity sign found was diarrhea in male animals of the high-dose group (LOAEL: 1792 mg/kg bw/day) (OECD SIDS, 2004). Therefore, the iron ion is the only toxicological relevant component of the registered substance.
3. ANALOGUE APPROACH JUSTIFICATION
Gluconates and their derivatives all belong to the aldonic acids (Escandar et al., 1992; Frutos et al., 1998) because they are derivatives of aldoses, sugars that contain one aldehyde group, which is oxidised to carboxylic group (Berg et al., 2007). They form lactone form, a ring structure the same as in the sugar’s cyclic hemiacetal form (Berg et al., 2007).
The dissociation of metal gluconate and glucoheptonate complexes at low pH values in the upper GI tract has been confirmed in a lot of investigations, which show gluconate and glucoheptonate complexes to be more stable at alkaline conditions, while the complexes were not stable enough to be detected at acidic conditions (Escandar et al., 1996; Sawyer, 1964; Gyurcsik and Nagy, 2000; Alekseev et al., 1998). Consequently, the metal ion and the gluconic or glucoheptonic acid anion will be subject to a more or less independent fate of absorption into the systemic circulation – independent from the organic moiety and will underlie normal physiological pathways responsible for metal uptake.
Considering this dissociation, the information that it has generally been shown by a substantial body of evidence, that the toxicity profiles of chelate compounds in general depend mainly on metal ion, its affinity to this metal, and their ability to supply or to sequester it from the body is a very useful information. In the OECD SIDS report is mentioned “Evidence from the reviewed literature suggests that the eventual toxicity of the gluconate salts would be attributable to the cation rather than of the gluconate moiety of these substances. Acute toxicity responses to the various gluconate salts are comparable with other salts of the same metals and long-term toxicities seem related to the tissue deposition of these metals. Because toxicological effects of these gluconates appear to be related to their cationic components, safe and acceptable levels in foods are limited only by the nature of the specific cations…(Life Science Research Office, 1978, cited in OECD SIDS (2004))”.
The released free gluconate or glucoheptonate anions, however, can in the posterior parts of the GI tract – in the small intestines, where pH raises - further sequester luminal or mucosal metal affecting the absorption. The impact of the released free gluconate or glucoheptonate anions on absorption of metals has been addressed by a lot of investigations, which showed that gluconate complexes actually enhanced absorption of metals increasing their bioavailability. Absorption of the nutrient metals was higher from gluconates than from the soluble inorganic compounds (i.e. Cousins, 1985, please refer to the detailed read-across statement attached in IUCLID section 13). Absorption of nutrient metals from glucoheptonate complexes seems to be equal to that from gluconate complexes (i.e. Durisova et al., 1985, please refer to the detailed read-across statement attached in IUCLID section 13).
After absorption, the above mentioned sugar residues, will all be metabolised by the pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) for the synthesis of the same 5-carbon sugars. In fact, no toxicity is attributed to the gluconate or glucoheptonate moiety up to considerable amounts.
In conclusion, gluconate and glucoheptonate anions form complexes with metals of the same geometry and stoichiometry. The same functional groups of the ligand are involved in the formation of coordinative bonds. Identical behaviour of gluconates and glucoheptonates depending on pH, molar concentration of metal: ligand components and physical state is verified by analytical methods. Based on the structural similarity of gluconates and glucoheptonates, their functional groups, composition, toxicodynamic, toxicokinetic, and toxicological behaviour, one can expect a very similar behaviour of these substances in living organisms.
Please refer also to the extended-read-across statement attached in section 13 of this IUCLID file
4. DATA MATRIX
The table attached in section 13 shows the available data relevant to justify the read-across from the source to the target chemical for the endpoint oral repeated dose toxicity. - Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Description (incidence and severity):
- no changes were observed in the general condition throughout the period of testing
- Mortality:
- no mortality observed
- Description (incidence):
- There was no statistically significant difference in the number and time of deaths between the treated and control groups.
- Body weight and weight changes:
- effects observed, treatment-related
- Description (incidence and severity):
- weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group
- Food consumption and compound intake (if feeding study):
- not examined
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- not specified
- Ophthalmological findings:
- not specified
- Haematological findings:
- not specified
- Clinical biochemistry findings:
- not specified
- Urinalysis findings:
- not specified
- Behaviour (functional findings):
- not specified
- Immunological findings:
- not specified
- Organ weight findings including organ / body weight ratios:
- not specified
- Gross pathological findings:
- not specified
- Neuropathological findings:
- not specified
- Histopathological findings: non-neoplastic:
- effects observed, non-treatment-related
- Description (incidence and severity):
- Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
- Histopathological findings: neoplastic:
- not specified
- Other effects:
- not specified
- Details on results:
- In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug: 1240-1350 mg/kgbw in 2.5% GDL group and 4920-5760 mg/kgbw in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
- Dose descriptor:
- NOAEL
- Remarks on result:
- not determinable
- Critical effects observed:
- no
- Conclusions:
- None of the repeated dose toxicity studies of any duration (4 weeks, 6 months, or 24 months) showed any significant toxicological effects of gluconates. Potential side effects were attributed to high doses of cation intake, evidenced by results from assays designed for the gluconate anion effect specifically. The NOAEL of sodium gluconate determined from the 28 days studies on rats was equal to 1000 mg/kg bw for males and 2000 mg/kg bw for females. On the basis of these data and considering that gluconates are used as food additives permitted in the EU following the Quantum Satis principle (no maximum level specified), further chronic toxicity tests are considered unnecessary.
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that glucono-delta-lactone is not toxic after repeated oral intake is important. - Executive summary:
In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug : 1240-1350 mg/kgbw. in 2.5% GDL group and 4920-5760 mg/kgbw. in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
These results are also relevant for iron glucoheptonate, as the glucoheptonate-residue is also a derivative of gluconic acid. Therefore, the fact that glucono-delta-lactone is not toxic after repeated oral intake is important.
Referenceopen allclose all
The group mean increases in bodyweight after 12 weeks are given in Table 1. Analysis of the combined data showed that at the higher dose level all four compounds significantly depressed growth rate in the male rats, but not in the females. At the lower dose level the depressions produced in the males by the fumarate and the gluconate were not significant (P = 0.05). None of the organ weights (expressed in mg/100 gr bodyweight) in the dosed groups differed significantly (P = 0.05) from those of the controls. Likewise no abnormalities were found in the red or total white cell counts or hemoglobin concentrations.
Apart from a slight and variable increase in iron deposition in the tissue phagocytes (e.g., Kupffer cells, pulmonary macrophages and adrenal cortical littoral cells), histologic examination of the organs listed above revealed no abnormalities that could be attributed to the drugs.
Table 1 -The Effects of 4 Iron Compounds on Growth Rate in Rats |
|||||||||||||
Daily oral dose |
Group mean increases in body weight ± S.E. (Gm.) after 12 weeks' dosing |
||||||||||||
Controls |
Fumarate |
Sulphate |
Gluconate |
Succinate |
|||||||||
male |
female |
male |
female |
male |
female |
male |
female |
male |
female |
||||
0 |
181 ± 13.6 |
92 ± 6.6 |
|
|
|
|
|
|
|
|
|||
50 |
156 ± 11.7 |
101 ± 6.8 |
129 ± 10.7 |
73 ± 11.7 |
172 ± 10.2 |
106 ± 11.1 |
145 ± 6.8 |
95 ± 8.3 |
|||||
100 |
|
|
136 ± 12.8 |
87 ± 10.7 |
113 ± 10.8 |
84 ± 8.8 |
136 ± 13.3 |
85 ± 7.5 |
135 ± 11.1 |
96 ± 12.4 |
|||
Repeated Oral Medication In The Cat
Since it had not been possible to obtain mortality following oral administration of large single doses of either compound in the cat, an effort was made to determine whether death would result from repeated medication with massive hypertherapeutic doses. Daily doses of 25, 50, 100, 200 and 400 mg/kg of ferrous sulfate and 100, 200, 400, 800 and 1600 mg/kg of ferrous gluconate were administered as a powder by capsule to 2 cats at each dose level 5 days a week for 2 weeks. No serious body weight changes or mortality occurred among the cats receiving ferrous gluconate. However, one cat on 400 mg/kg of ferrous sulfate died following the fifth dose. Some impairment of appetite occurred in the second cat at this dose level, but no serious loss in weight occurred and the cat survived the full medication schedule. Occasional vomiting and diarrhea occurred at the lower dosages with both compounds as noted in Table 1. The intensity of the emesis increased with increase of dosage and was associated with a decrease in the incidence of diarrhea. The emesis appeared to be entirely local in effect, since it occurred in less than an hour after medication. Other than the emesis, the cats appeared to suffer no ill effects from the medication. The appetite except at the highest dosages remained normal in every cat.
Table 1 - Effects Of Repeated Massive Oral Dosage (5 Days A Week For 2 Weeks) Of Ferrous Sulfate (FeSO4-7H2O) and Ferrous Gluconate (Fe[C6H11O7]2-2H2O) in Cats |
|||||
Compound |
As Salt |
As Fe++ |
Mortality |
Emetic Effects |
Diarrhea |
Ferrous sulfate |
25 |
5.0 |
0/2 |
Occ.*, one cat |
None |
50 |
10.0 |
0/2 |
Occ., one cat |
Occ., both cats |
|
100 |
20.1 |
0/2 |
Frequ., both cats |
Occ., both cats |
|
200 |
40.2 |
0/2 |
Frequ., both cats |
Frequ., both cats |
|
400 |
80.4 |
1/2 |
Daily |
None |
|
(7th day) |
|||||
Ferrous gluconate |
100 |
11.6 |
0/2 |
Occ., one cat |
Occ., one cat |
200 |
23.2 |
0/2 |
Occ., both cats |
Frequ., both cats |
|
400 |
46.4 |
0/2 |
Frequ., both cats |
Occ., both cats |
|
800 |
92.8 |
0/2 |
Frequ., both cats |
Occ., both cats |
|
1600 |
185.6 |
0/2 |
Daily |
Occ., both cats |
|
*occ. = occational; Frequ. = Frequent
Discussion
In the present study, no mortality was observed with single oral doses of ferrous sulfate up to and including 200 mg/kg. When given by repeated oral administration, however, one of two cats died at the end of the first week at a dose of 400 mg/kg of ferrous sulfate. Copious vomiting was encountered in the cat, which tended to interfere with attempts to estimate the acute oral lethal dose of ferrous sulfate in these two species. The fact that copious and effective emesis interfered with the estimation of the acute oral lethal dose of ferrous sulfate in both the cat and dog indicates that this protective mechanism may be better developed in these two species than it is in the human.
Summary
The results of a direct comparison of the acute systemic and local toxicity of ferrous sulfate (FeSO4*7H2O) and ferrous gluconate (Fe[C6H11O7]2*2H2O) in experimental animals may be summarized as follows:
Daily oral administration of ferrous gluconate powder by capsule to cats, 5 days a week for 2 weeks at the hypertherapeutic dosages of 100 to 1600 mg/kg produced no mortality and no evidence of cumulative toxicity. Emesis and diarrhea were noted at all dose levels. Emesis was particularly prompt and copious at the highest dose levels.
The magnitude of the acute oral toxicity values when compared with the acute intravenous figures in mice indicates a relatively low order of absorption from the intestinal tract. An additional safety factor is evident from the oral studies in the cat and the dog in which the local irritant effects induce a protective emesis. These data suggest prompt, gentle gastric lavage along with supportive therapy for shock as an effective emergency measure in those cases where, for any reason, vomiting does not occur spontaneously following oral ingestion of ferrus sulfate, ferrous gluconate or other soluble iron salts.
Pates enriched with the two sources of iron, ferric pyrophosphate encapsulated in liposomes and ferrous gluconate, were similar in colour and smell, and were well accepted by the rats.
In the AIN-93G diet, fat is provided by soybean oil, with a high content in polyunsaturated fatty acids (PUFA), mainly linoleic acid (54%), while pate content in PUFA was much lower, and contained 49% of monounsaturated fatty acids (MUFA, mainly oleic acid) and 35% of saturated fatty acids (SFA, mainly palmitic acid). Therefore, the pate used in the present study presented a more saturated lipid profile than the control diet which exclusively contained soybean oil.
Results of food intake are in agreement with previous reports indicating that saturated fat compared to polyunsaturated presents better sensory acceptability. However, the higher food consumption observed in the two pate groups did not lead to higher body weight because the control diet, rich in linoleic and linolenic acids, is the most adequate diet for rats at a growing stage.
Table 1 - Food intake, body weight and food efficiency in rats |
||||
Sampling and Variables |
Rats Diet1 |
ANOVA |
||
Control |
Ferric Pyrophosphate |
Ferrous Gluconate |
||
Days 1-7 |
||||
Weight (g) day 1 |
40.40 ± 0.68 |
40.58 ± 0.64 |
40.55 ± 0.49 |
NS |
Food intake (g/day) |
9.19 ± 0.32 |
9.79 ± 0.46 |
10.27 ± 0.48 |
NS |
Food efficiency |
0.47 ± 0.01 |
0.45 ± 0.02 |
0.42 ± 0.01 |
NS |
Days 7-14 |
||||
Weight (g) day 7 |
70.63 ± 1.97 |
71.01 ± 1.43 |
70.23 ± 1.47 |
NS |
Food intake (g/day) |
13.38 ± 0.46a |
15.87 ± 0.47b |
15.84 ± 0.72b |
<0.01 |
Food efficiency |
0.41 ± 0.01a |
0.35 ± 0.01b |
0.34 ± 0.01b |
<0.001 |
Days 14-21 |
||||
Weight (g) day 14 |
109.64 ± 4.07 |
110.08 ± 3.36 |
107.99 ± 3.28 |
NS |
Food intake (g/day) |
15.56 ± 0.82a |
20.31 ± 1.46b |
18.71 ± 1.29b |
<0.05 |
Food efficiency |
0.29 ± 0.03 |
0.22 ± 0.02 |
0.26 ± 0.03 |
NS |
Days 21-28 |
||||
Weight (g) day 21 |
141.75 ± 7.79 |
141.00 ± 5.71 |
145.2 ± 4.72 |
NS |
Food intake (g/day) |
16.17 ± 1.13a |
20.13 ± 1.08b |
19.62 ± 1.18b |
<0.05 |
Food efficiency |
0.31 ± 0.04 |
0.29 ± 0.03 |
0.27 ± 0.03 |
NS |
Weight (g) day 28 |
178.35 ± 13.92 |
182.70 ± 9.60 |
183.13 ± 9.54 |
NS |
Values are mean ± SEM of eight animals per group. Values in the same arrow followed by different superscripts are statistically significant. NS = non-significant. |
||||
Iron intake during the last week of the assay was higher in the pate groups than in the control group (P < 0.01) due to the higher food intake, being significantly more elevated in the case of the ferric pyrophosphate group.
However, there were no significant differences due to the iron salt. Differences in faecal, apparent iron absorption and %A/I between the three groups were not significant (Table 3). Accordingly, the iron content and concentration of the spleen and liver did not show differences depending on whether the rats consumed diets with or without pate, or the iron salt (Table 2).
Table 2 - Iron content in liver and spleen of rats |
||||||
|
Liver1 |
Spleen1 |
||||
Groups |
Weight (g) |
Iron Content (mg) |
Iron Conc. (µg/g) |
Weight (g) |
Iron Content (µg) |
Iron Conc.. (µg/g) |
Control |
6.32 ± 0.49 |
1.16 ± 0.22 |
199.9 ± 46.4 |
0.57 ± 0.05 |
187.1 ± 43.9 |
304.1 ± 52.1 |
Ferric pyrophosphate |
6.18 ± 0.48 |
1.03 ± 0.09 |
175.6 ± 23.0 |
0.58 ± 0.07 |
142.8 ± 32.4 |
233.8 ± 19.4 |
Ferrous gluconate |
6.28 ± 0.44 |
1.13 ± 0.07 |
184.8 ± 15.6 |
0.50 ± 0.05 |
127.6 ± 30.8 |
248.0 ± 35.5 |
ANOVA |
NS |
NS |
NS |
NS |
NS |
NS |
1 Values are mean ± SEM of eight animals per group. NS = non-significant. |
||||||
Table 3 - Iron absorption in the three groups of rats |
||||
Groups |
Iron1(mg/day) |
|||
Ingested |
Fecal |
Absorbed |
% A/I |
|
Control |
0.95 ± 0.06a |
0.46 ± 0.03 |
0.49 ± 0.03 |
51.89 ± 1.54 |
Ferric pyrophosphate |
1.23 ± 0.06b |
0.63 ± 0.08 |
0.60 ± 0.10 |
48.20 ± 7.46 |
Ferrous gluconate |
1.18 ± 0.06ab |
0.59 ± 0.06 |
0.58 ± 0.05 |
49.79 ± 3.97 |
ANOVA |
<0.01 |
NS |
NS |
NS |
Values are mean ± SEM of eight animals per group. Values in the same column followed by different superscripts are statistically significant. NS = non-significant. |
||||
The results indicated that iron bioavailability of pate enriched with ferrous gluconate or ferric pyrophosphate encapsulated in liposomes was similar. These results were in agreement with in vitro iron availability results using Caco-2 cells, that showed similar iron availabilities with Lipofer®, ferrous lactate and ferrous sulphate, which are chemically similar to ferrous gluconate (Kloots et al., 2004). Ferrous gluconate, sulphate and lactate belong to the group of freely water soluble iron compounds. Thanks to being highly soluble in water, they enter the common pool on non-heme iron completely upon digestion and present high bioavailability.
The present results support that encapsulation of ferric pyrophosphate, as in Lipofer®, protects iron from forming non-absorbable compounds and improves iron bioavailability.
When encapsulating, the effects on iron bioavailability depended on the thickness of the capsule and the coating material (Hurrell, 2002) as well as on the ratio capsule/substract (Wegmüller et al., 2004).
Lipofer® is a complex of ferric pyrophosphate, with an average particle size of 7 μm, encapsulated with starch and lecithin.
Lipofer® used in this study presented a ratio of 30 : 70, which improved iron bioavailability resulting similar to that of ferrous gluconate.
This is the first study that shows that lipofer® included in a meat product constitutes an iron supplement of high bioavailability. In addition, it is generally well accepted by a wide range of population and depending on the food process applied can be stored, either refrigerated or at room temperature, for long periods of time. Further studies are needed to validate these results in humans considering technological, cost-effectiveness and health aspects.
A 28-day study was conducted by feeding rats by gavage with sodium gluconate at doses of 0, 500, 1000, 2000 mg/kg bw in water at a volume of 1 mL/ 100g bw. No death or clinical signs of abnormality were observed in any of the groups. Histopathological examination showed a thickening of the limiting ridge of the stomach in 5 out of 12 males at 2000 mg/kg bw per day dose. No toxic changes associated with the test article were detected. As the limiting ridge is a tissue specific to rodents, this lesion is not toxicologically relevant for humans. Other lesions occurred incidentally and were not treatment -related.
The NOAEL was estimated to be 1000 mg/kg bw/day for males and 2000 mg/kg bw/day for female (Mochizuki, M, Bozo Research Center, 1995a).
A 28-day toxicity study in rats fed with a diet containing up to 5% w/w sodium gluconate (max. 4100 mg/kg bw for males and 4400 mg/kg bw for females) was conducted using a control group receiving equivalent concentration of sodium in the form of NaCl in order to differentiate the potential effects of high doses of sodium intake. No deaths occurred during the study period. No revisions in the general condition, body weight, or food and water intake were observed in the animals over the study period. No changes were observed in the investigated ophthalmologic tests, urinalysis, hematology and blood chemistry over the study period. In addition, histopathological examination indicated no adverse effects as a result of the treatment regime. Statistically significant differences in some urinary parameters reported in animals receiving 2.5 or 5% sodium gluconate were comparable to those observed in the NaCl control group, and were interpreted as related to the high sodium concentration of the diet.
The authors concluded that the NOAEL was 5% (equal to 4100 mg/kg bw per day). However, The JECFA committee who evaluated this report has concluded that the study was not suitable for identifying a NOAEL because of the small group sizes and the positive findings in the qualitative analysis, even if they have acknowledged that the effects shown in the qualitative urine analyses were related to the high sodium intake (Mochizuki, M. Bozo Research Center, 1997). Nonetheless, this study demonstrates the lack of effects of the gluconate anion even in large doses as the urinary effects were attributed to the high sodium intake and was therefore considered as critical for this endpoint.
Repeated toxicity studies were also performed on Beagle dogs with sodium gluconate administered orally for 4 weeks at 500, 1000, 2000 mg/kg bw doses. None of the animals died during the period of treatment in any dose group and no significantly toxicologically changes were detected in the body weight, food intake, water intake, urinalysis, haematological test, blood chemistry analysis, ophthalmologic test, electrocardiography, autopsy and organ weight or in histopathological examination. However, increased frequency of vomiting and loose or watery stools were observed in the 1000 and 2000 mg/kg bw dose groups, as compared to controls.
On the basis of these results, the non-toxic dose was estimated to be 500 mg/kg bw / day. However, the toxicological effects observed (vomiting, passage of loose or watery stools) were considered extremely slight since other tests did not show the same changes (Okamoto, M. Bozo Research Center, 1995a).
Glucono-delta-lactone (250, 500, 1000, 2000 and 4000 mg/kgbw for 6 months) was orally administered to Sprague-Dawley rats. In all dose groups, thickening of the stratified squamous epithelium was detected at the anterior stomach, particularly the transitional area continuous with the pyloric stomach; the frequency and severity of this thickening increased with the dose. In high dose groups, submucosal inflammatory cell infiltration was also detected, but this change was not statistically significant. No deaths or other abnormalities were detected (Fukuhara K, 1978). In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug : 1240-1350 mg/kgbw in 2.5% GDL group and 4920-5760 mg/kgbw in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
In Wistar rats fed for 24 months with a diet containing 2.5% and 10% of glucono-delta-lactone (the total intake of the drug: 1240-1350 mg/kgbw in 2.5% GDL group and 4920-5760 mg/kgbw in the 10 % GDL group), no changes were observed in the general condition throughout the period of testing, but weight gain tended to be slightly reduced 2-3 months after the initiation of the test feeding in 10% GDL group. There was no statistically significant difference in the number and time of deaths between the treated and control groups. Histopathological changes accompanying aging were observed in all groups including the controls, but no specific changes likely to be associated with the test substance were detected (Fukuhara K, 1978a).
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEL
- 427.35 mg/kg bw/day
- Study duration:
- subchronic
- Species:
- rat
- Quality of whole database:
- The quality of the whole database is considered sufficient for estimation of repeated doese toxicity potential, because of the multipicity of available data for the different read-across substances
Repeated dose toxicity: inhalation - systemic effects
Endpoint conclusion
- Endpoint conclusion:
- no study available
Repeated dose toxicity: inhalation - local effects
Endpoint conclusion
- Endpoint conclusion:
- no study available
Repeated dose toxicity: dermal - systemic effects
Endpoint conclusion
- Endpoint conclusion:
- no study available
Repeated dose toxicity: dermal - local effects
Endpoint conclusion
- Endpoint conclusion:
- no study available
Additional information
Repeated dose toxicity: other routes:
Data on sodium ferric gluconate complex in sucrose injection
Repeated dose toxicity studies have been carried out in rats and rabbits (sanofi-aventis Canada Inc, 2009).
In a subacute repeated dose study, the rats (20M and 20F) received Ferrlecit (sodium ferric gluconate complex in sucrose injection) via intravenous injection at doses of 42.25 mg Fe/kg for 28 days. No deaths were observed. Rats showed evidence of pain and aggressiveness. Body weight gain was inhibited and food consumption dropped. Leukocytes increased at four weeks. Plasma iron content increased and iron binding capacity increased in all except the females in one group. Hemorrhage and some thrombosis and necrosis occurred at the injection site. Gross examination at necropsy revealed only enlargement of the spleen. Some organ weights including the heart, lungs, kidneys, adrenals, thymus, hypophysis, gonads, thyroid, and liver, were reduced compared to controls. In almost all treated animals, a discrete reticular activation was found on the hilus and in the alveolar parenchyma. A small bladder papilloma was seen in a treated male rat. All treated animals revealed pronounced siderophilic deposition in the lymphatic reticulum, but no signs of system activation.
In a subchronic repeated dose study, the rats (20M and 20F) received Ferrlecit via intravenous injection at doses of 2.5, 6.25 and 12.5 mg Fe/kg for 84 days. Body weight of the males in the 6.25 and 12.50 mg/kg groups was slightly, but not dose dependently reduced. A slight reduction in body weight was found in the 12.50 mg/kg group females. Serum iron values were increased dose-dependently in all groups of both sexes. Total lipids were increased in both sexes of the 6.25 and 12.50 mg/kg groups. Phospholipids were increased in the males of the 12.50 mg/kg group and the females of the 6.25 and 12.5 mg/kg groups. Total cholesterol was dose-dependently increased in the males of all groups and in the 12.50 mg/kg group females. Triglycerides were elevated in the 6.25 and 12.50 mg/kg group females. Urinalysis revealed a substantial increase in protein values in the 6.25 mg/kg group males. Organs revealed light to dark brown coloration in virtually all rats of the 12.50 mg/kg group: pancreas, spleen, liver, adrenals, intestine, and subcutaneous fatty tissue. Adrenals were reduced in size and the spleen and liver enlarged. The liver weights in the 6.25 and 12.50 mg/kg group males and in the 12.50 mg/kg group females were considerably increased. Spleen weights were increased dose dependently in both sexes of the 6.25 and 12.50 mg/kg groups. Histology examination revealed increased deposits of iron-containing pigment in the liver, spleen, lymph nodes, and kidneys, and sporadic deposits in other organs, apparently dose-dependent.
The results of the animals treated with 2.5 mg Fe/kg were not considered adverse, therfore a NOAEC of 2.5 mg Fe/kg was derived. This corresponds to a NOAEC of 17.71 mg/kg bw/bayof iron glucoheptonate
In subchronic repeated dose studies in rabbits, the rabbits (10 animals) received via intravenous injection Ferrlecit at doses of 1.875 mg Fe/kg for 90 days. No changes in the hematology or blood chemistry tests except for an increase in hemoglobin and SGPT. No signs of toxic effects observed in organ weights, macroscopic, or microscopic examinations. No signs of iron deposits in duodenum, pancreas, adrenal cortex, or liver.
The results of the animals treated with 1.875 mg Fe/kg were not considered adverse, therefore a NOAEC of 1.875 mg Fe/kg was derived. This corresponds to aNOAEC of 17.49 mg/kg bw/day of iron glucoheptonate.
These results are of high relevance for the substance iron glucoheptonate, since sodium ferric gluconate complex in sucrose injection is a highly recommended read across substance, due to its similar chemical behaviour and its similar uses.
Justification for classification or non-classification
On the basis of the available data the registered substance is not classified according to European Regulation (EC) No 1272/2008.
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