Methyl 12-hydroxyoctadecanoate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

The information was published in a peer reviewed journal, and was reviewed by the Cosmetic Ingredient Review Expert Panel who judged the study as scientifically valid for risk assessment, classification and labelling.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

predates OECD guideline

GLP compliance:

no

Remarks:

predates GLP

Specific details on test material used for the study:

Hydrogenated Castor Oil (HCO) was a granulated powder containing 86.5% 12-hydroxystearic acid, 10.3% nonoxygenated acids, and 3.2% 12-ketostearic acid. The melting point was reported to be above 80 degrees C.

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Slonaker substrain of Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Animals: male and female rats (Slonaker substrain of albino Wistar strain). The preliminary studies utilized three weanling female rats per dose group; the main study utilized 15 male rats per dose group (body weight ranging from 43 to 83 g). They were maintained on Purina Laboratory Chow. Food and water were available ad libitum. Body weight and food consumption records (by group) were maintained weekly. Live weight data were statistically analyzed at the end of the experiment to indicate the influence of diet. Differences in initial weight were removed in order to compare live weights on the basis of the same initial weight for each rat. Weights of all rats living at a particular time were included in calculations of average weight and weight gain.

Route of administration:

oral: feed

Vehicle:

corn oil

Remarks:

in second preliminary and main studies

Details on oral exposure:

Diets were prepared from Purina Laboratory Chow. For the first preliminary study, HCO in the form of a powder was added to the chow at the expense of an equal amount of the rat diet. For the second preliminary and main studies, HCO was melted and mixed with corn oil, which was then blended with the chow.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

16 weeks

Frequency of treatment:

daily

Dose / conc.:

0 other: %

Dose / conc.:

1 other: %

Remarks:

(w/w), in the diet

Dose / conc.:

10 other: %

Remarks:

(w/w), in the diet

Control animals:

yes

yes, concurrent vehicle

Details on study design:

The objectives of the in vivo repeated dose toxicity study in rats was to determine whether rats on diets containing hydrogenated castor oil would absorb hydroxystearic acid and incorporate it, whether rats on these diets would grow normally, and whether deposited hydroxystearic acid would be metabolized.

In a preliminary feeding trial, HCO (powder) was added directly to the food and mixed. Dose levels were 0%, 5%, 10%, and 20% Hydrogenated Castor Oil [HCO] (effective concentrations of 0%, 4.33%, 8.65%, and 17.3%, respectively) in the diet. There were 3 rats per dose group, and rats were fed for 90 days. At the end of the experiment, the rats were sacrificed and necropsied; organ weights were recorded and tissues were preserved in 10% formaldehyde for microscopic histopathology examination. Prior to necropsy, blood samples were obtained for hematological evaluation. In a second preliminary feeding trial, HCO was dissolved in corn oil before being added to the diet. The levels of HCO fed to rats were 0%, 1%, 5% and 10%, and the amounts of corn oil added to each diet were 20%, 19%, 15% and 10%, respectively. Three rats per dose group were fed for 90 days. At 90 days, blood samples were taken for hematology; the rats were sacrificed and necropsied; and organs were weighed and examined microscopically for adverse effects.

Fifteen male rats were assigned to each dose group in the main study in order to give the same mean weight per group. After eight weeks of feeding, half of the groups of rats on HCO diets was given the corn oil diet until the end of the experiment at 16 weeks. Therefore, data was generated for the following 4 groups: 1% HCO for 16 weeks; 1% HCO for 8 weeks, then corn oil for 8 weeks; 10% HCO for 16 weeks; 10% HCO for 8 weeks, then corn oil for 8 weeks. Body weights were statistically analyzed (p ≥ 0.05) to indicate the influence of diet.

At the end of the study, blood was taken for hematological analysis. Animals were weighed. Histopathology analysis was undertaken on tissue samples from major organs. Analysis of lipid was undertaken on excised abdominal fat or on extracted carcass lipids. In preliminary experiments, excised abdominal adipose tissue from each group was pooled; in the main experiment, adipose tissue from rats in various dietary groups was analyzed individually (not pooled). Methyl esters were recovered from the extracted lipids, chromatographed and identified.

Observations and examinations performed and frequency:

Body weights were taken initially and at 4, 8, 12, and 16 weeks.

Sacrifice and pathology:

No information is given on euthanasia. Blood was taken prior to sacrifice for hematology assessment. Histopathology examination was undertaken.

Statistics:

Differences between treatment groups were assessed with p > 0.05.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

At 12 and 16 weeks, weight gain in rats in the 10% HCO diet was significantly less than controls. At 16 weeks, weight gain in rats on the 10% HCO diet for 8 weeks and corn oil for 8 weeks also was significantly less than controls. Weight gain in rats on the 1% HCO diet was not statistically significantly different from controls.

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

An explanation for the lesser growth of rats on the 10% HCO diet is that the HCO may have been difficult to absorb from the gastrointestinal tract, based on a rat caloric availability assay (Rice et al., J. Nutr. 61: 253-266, 1957). In the first preliminary study, 9-14% of the powdered HCO was digested and represented only 18% of the caloric availability of an equivalent amount of corn oil. In the second preliminary study of a HCO-corn oil blend (1:3), the digestability values ranged from 27-64% of the corn oil diet. Thus the difference in weight gains could be due to the lower caloric value of the diet containing HCO.

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Analysis of abdominal adipose tissue and carcass lipid showed a dose-dependent increase in the amount of hydroxy fatty acids. This content decreased when HCO was removed from the diet and replaced with corn oil.

Details on results:

In the preliminary feeding trial, a reduced growth rate was observed in rats fed 8.65% and 17.3% HCO, and was the only abnormality that was noted. The authors stated that it is likely that HCO was poorly digested (because of its high melting point); the poor body weight gains may have been due to the lower caloric density of the diets containing HCO at concentrations ≥8.65%.

The experimental trial was repeated with HCO at concentrations of 0%, 1%, 5%, and 10% in corn oil (effective concentrations of 0.865%, 4.33%, and 8.65%, respectively). The growth rate for rats fed 10% Hydrogenated Castor Oil (highest dose group) was equivalent to that of the other dietary groups. Based on organ weight determinations and the results of hematological and microscopic evaluations, no adverse effects were observed.

In the 16-week main feeding study, the effective dietary concentrations of Hydrogenated Castor Oil in the 1% and 10% diets were 0.865% and 8.65%, respectively. The control group received 20% corn oil in the diet for 16 weeks.

At 4, 8, 12, and 16 weeks, the number of animals on the HCO diets that were alive was 33, 30, 12, and 6 rats, respectively. The corresponding number of rats remaining on the control diet was 15, 15, 12, and 6. There were no mortalities in any group.

Hydroxylipids increased in the animals fed both concentrations of HCO in the diet, as a percentage of dry carcass weight. After 4 weeks into the main experiment in animals on the 1% HCO diet, HCO-derived fatty acids accounted for 0.90% (by weight) of the abdominal fat fatty acids. The maximum content of HCO-derived hydroxyacids in body lipids was 4.4% in abdominal fat at 4 weeks on the 10% HCO diet. It appears that hydroxyacids derived from HCO in the diet preferentially find their way into abdominal fat compared to other body (carcass) lipids. Compared to the abdominal fatty acids, the acids obtained from the carcass lipids contained a smaller proportion (0.28% over the 8- to 16-week feeding period) of HCO-derived hydroxyacids. The total content of HCO-derived hydroxyacids (combined abdominal fat and carcass lipids) was 6.28% in rats fed 10% HCO in the diet for 8 weeks.

When rats were changed from the HCO diet to the control diet, a rapid decrease in the amount of HCO-derived hydroxy fatty acids in the tissues occurred. Loss of hydroxyl fatty acids was rats on the 10% HCO diet was more pronounced that in those on the 1% HCO diet. The proportion of HCO-derived hydroxyacids decreased from 0.90% to 0.35% over the 8- to 16-week feeding period in animals fed the 1% HCO diet. In animals fed 10% HCO in the diet for only 8 of 16 weeks, this proportion had decreased from 6% to <2%, equally distributed in abdominal fat and carcass lipids. Hydroxystearic acid was also found in animals on the control diet (corn oil).

Weight differences due to the different diets at 4 and 8 weeks were not statistically significant at the 95% level. However, at 12 weeks, rats on the 10% HCO diet weighed significantly less than rats on the control diet or 1% HCO diet. At 16 weeks, the weight gain of rats on the control diet was significantly greater than that of rats on the 10% HCO diet for 16 weeks or on the 10% HCO diet for 8 weeks + control diet for the remaining 8 weeks. The weight gain of rats on the 1% HCO diet was not significantly different from that of rats on the control diet. Except for the reduced growth rate in rats receiving the 10% HCO diet, no adverse effects were observed.

Key result

Dose descriptor:

LOAEL

Effect level:

10 other: % (w/w) in the diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

Key result

Dose descriptor:

NOEL

Effect level:

1 other: % (w/w) in the diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

Key result

Critical effects observed:

no

Conclusions:

Rats ingesting 1% HCO dissolved in corn oil (0.865% equivalent) in a laboratory chow diet gained weight in a similar manner as rats on a control diet (20% corn oil). Rats ingesting 10% HCO dissolved in corn oil (8.65% equivalent) for 8 to 16 weeks demonstrated significantly decreased body weight gain. This may be explained by the 10% diet having 27% of the caloric availability of the control diet. Hydroxy fatty acids were detected in adipose tissue and carcass lipids in a dose-responsive manner. There were no other adverse effects observed. The NOEL is approximately 1% HCO in the diet of Wistar rats for 16 weeks; the LOAEL is 10% HCO in the diet.

Data source

Reference

Reference Type:

publication

Title:

Hydroxystearic acid deposition and metabolism in rats fed hydrogenated castor oil

Author:

Binder RG, Booth AN, Robbins DJ and Fuller G

Year:

1970

Bibliographic source:

Lipids 5(10): 832-837

Materials and methods

Objective of study:

absorption

metabolism

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Version / remarks:

Predates guideline. Not a TK study but absorption and metabolism addressed

Deviations:

yes

Remarks:

no radiolabel used. Repeated dose rather than single dose. Animals were not fasted prior to dosing. Typical PK parameters were not all investigated or reported.

Principles of method if other than guideline:

Hydroxylated fatty acids were assayed in the fat of rats fed up to 10% hydrogenated castor oi In a subchronic dietary study

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Fatty acids, castor-oil, hydrogenated

EC Number:

263-131-4

EC Name:

Fatty acids, castor-oil, hydrogenated

Cas Number:

61790-39-4

IUPAC Name:

fatty acids, castor-oil, hydrogenated

Test material form:

solid

Details on test material:

As per the 2007 CIR Final Report on Ricinus communis, Hydrogenated Castor Oil consists primarily of glyceryl-tri-hydroxystearate (Nikitis and McEwen, 1990). The National Formulary (Committee of Revision of the United States Pharmacopeial Convention 2004b) has published the following requirements for Hydrogenated Castor Oil: free fatty acids (free fatty acids in 20 g require for neutralization not more than 11.0 ml of 0.1 N sodium hydroxide), heavy metals (0.001%), hydroxyl value (between 154 and 162), iodine value (not more than 5), and saponification value (between 176 and 182).

Specific details on test material used for the study:

Hydrogenated Castor Oil (HCO) was a granulated powder containing 86.5% 12-hydroxystearic acid, 10.3% nonoxygenated acids, and 3.2% 12-ketostearic acid. The melting point was reported to be above 80 degrees C.

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Slonaker substrain of albino Wistar strain

Sex:

male/female

Details on test animals or test system and environmental conditions:

Animals: male and female rats (Slonaker substrain of albino Wistar strain). The preliminary studies utilized three weanling female rats per dose group; the main study utilized 15 male rats per dose group (body weight ranging from 43 to 83 g). They were maintained on Purina Laboratory Chow. Food and water were available ad libitum. Body weight and food consumption records (by group) were maintained weekly. Live weight data were statistically analyzed at the end of the experiment to indicate the influence of diet. Differences in initial weight were removed in order to compare live weights on the basis of the same initial weight for each rat. Weights of all rats living at a particular time were included in calculations of average weight and weight gain.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

corn oil

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 other: %

Doses / concentrations 2

Dose / conc.:

1 other: %

Remarks:

(w/w), dissolved in corn oil

Doses / concentrations 3

Dose / conc.:

10 other: %

Remarks:

(w/w), dissolved in corn oil

No. of animals per sex per dose / concentration:

15

Control animals:

yes, concurrent vehicle

Details on study design:

Diets were prepared from Purina Laboratory Chow. For the first preliminary study, HCO in the form of a powder was added to the chow at the expense of an equal amount of the rat diet. For the second preliminary and main studies, HCO was melted and mixed with corn oil, which was then blended with the chow (representing 80% of each diet).

Details on dosing and sampling:

In the main study, fifteen male rats were assigned to each dose group in the main study in order to give the same mean weight per group. Animals were fed the diet for eight weeks, then half of the rats on the HCO diets were given the control corn oil diet until the end of the experiment at 16 weeks. Data was generated for the following 4 groups: 1% HCO for 16 weeks; 1% HCO for 8 weeks, then corn oil diet for 8 weeks; 10% HCO for 16 weeks; 10% HCO for 8 weeks, then corn oil diet for 8 weeks. Body weights were statistically analyzed (p ≥ 0.05) to indicate the influence of diet.

After 4 weeks of feeding, some of the animals on the 1% HCO (three rats) and 10% HCO (three rats) diets were necropsied and excised abdominal adipose tissue from each group was pooled. At weeks 4 and 8, sets of three rats on the corn oil diet were used. At the end of the 16-week feeding period, adipose tissue from rats in the various dietary groups was analyzed. Adipose tissue was not pooled. After 8, 12, and 16 weeks, lipids were extracted from three rats on each diet. Methyl esters were recovered from the extracted lipids and chromatographed. Extractions of duplicate carcass fat samples were reproducible within 4-5%.

Statistics:

Group differences were considered significant at p< 0.05. Reproducibility was greater than 95%.

Results and discussion

Main ADME results

Type:

absorption

Results:

Hydroxylated fatty acids were detected in carcass and adipose fat of rats fed hydrogenated castor oil in the diet.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Hydroxystearic acid was deposited in abdominal fat and other body lipids. In all cases, it was accompanied by hydroxypalmitic acid, hydroxymyristic acid, and hydroxylauric acid (all are hydroxy-stearic acid metabolites). The percent composition of these HCO-derived hydroxy fatty acids in rat lipids was as follows: 12-hydroxystearic acid (81%), 10-hydroxypalmitic acid (17%), 8-hydroxymyristic acid (1.6%), and 6-hydroxylauric acid (0.4%). This is consistent with metabolism which occurs by successive losses of two-carbon units from the carboxyl end of the fatty acid chain.
Hydroxylipids increased in the animals fed both concentrations of HCO in the diet, as a percentage of dry carcass weight. After 4 weeks into the main experiment in animals on the 1% HCO diet, HCO-derived fatty acids accounted for 0.90% (by weight) of the abdominal fat fatty acids. The maximum content of HCO-derived hydroxyacids in body lipids was 4.4% in abdominal fat at 4 weeks on the 10% HCO diet. It appears that hydroxyacids derived from HCO in the diet preferentially find their way into abdominal fat compared to other body (carcass) lipids. Compared to the abdominal fatty acids, the acids obtained from the carcass lipids contained a smaller proportion (0.28% over the 8- to 16-week feeding period) of HCO-derived hydroxyacids. The total content of HCO-derived hydroxyacids (combined abdominal fat and carcass lipids) was 6.28% in rats fed 10% HCO in the diet for 8 weeks.

When rats were changed from the HCO diet to the control diet, a rapid decrease in the amount of HCO-derived hydroxy fatty acids in the tissues occurred. Loss of hydroxyl fatty acids was rats on the 10% HCO diet was more pronounced that in those on the 1% HCO diet. The proportion of HCO-derived hydroxyacids decreased from 0.90% to 0.35% over the 8- to 16-week feeding period in animals fed the 1% HCO diet. In animals fed 10% HCO in the diet for only 8 of 16 weeks, this proportion had decreased from 6% to <2%, equally distributed in abdominal fat and carcass lipids. Hydroxystearic acid was also found in animals on the control diet (corn oil), consistent with other studies examining the content of hydroxyacids in the rat body, as well as in humans and canines, and suggests that hydroxyacid formation is a normal phenomenon.

Details on distribution in tissues:

Hydroxyacids were found in adipose tissue and carcass fat after the feeding of rats of up to 10% HCO in the diet. This is consistent with lipid formation from fats and triglycerides in the gut after intake of lipid containing food.

Details on excretion:

no data

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Hydroxystearic acid was deposited in abdominal fat and other body lipids. In all cases, it was accompanied by hydroxypalmitic acid, hydroxymyristic acid, and hydroxylauric acid (all are hydroxy-stearic acid metabolites). The percent composition of these HCO-derived hydroxy fatty acids in rat lipids was as follows: 12-hydroxystearic acid (81%), 10-hydroxypalmitic acid (17%), 8-hydroxymyristic acid (1.6%), and 6-hydroxylauric acid (0.4%). This is consistent with metabolism which occurs by successive losses of two-carbon units from the carboxyl end of the fatty acid chain.

Any other information on results incl. tables

Table 1: Mean Hydroxy Fatty Acid Content in Rats (Binder et al., 1970).

 

		Week
Regimen	Tissue	4	8	12	16
		Weight Percent of carcass fatty acids
Corn Oil	Abdom fat	-	-	0.027	0.020
	Carcass	-	0.43	0.022	0.023
1% HCO	Abdom fat	0.97	0.34	0.36	0.35
	Carcass	-	0.27	0.29	0.28
1% HCO x 8 wks then corn oil x 8 wks	Abdom fat	-	-	0.087	0.048
	Carcass	-	-	0.079	0.042
10% HCO	Abdom fat	4.40	4.03	2.28	1.67
	Carcass	-	2.25	1.81	1.91
10% HCO x 8 wks then corn oil x 8 weks	Abdom fat	-	-	0.87	0.12
	Carcass	-	-	0.27	0.10

Standard deviation values are available in the original reference article

 

Applicant's summary and conclusion

Conclusions:

Rats ingesting 1% and 10% hydrogenated castor oil (HCO) dissolved in corn oil (0.865% or 8.65% equivalent) in a laboratory chow diet for 8-16 weeks showed increased accumulation of hydroxy fatty acids in body fat reserves (primarily adipose tissue) when compared with rats on a control diet (20% corn oil). This is consistent with utilization of hydroxylated fatty acids (from HCO) in the synthesis of triglycerides stored in fat tissue. Hydroxy fatty acids were present at a low level in the fat of rats fed the control diet.