Isostearic acid, esters with methyl α-D-glucoside

Endpoint summary

Additional information

Justification for read across

Based on the structural analogue approach to Isostearic acid, esters with methyl α-D-glucoside read across from Stearic acid, esters with methyl α-D-glucoside is considered acceptable.

The structural analogue approach is scientifically justified by close similarities with regard to physico-chemical properties and structural aspects. With regard to the environmental fate side this approach is based on standard biodegradation studies. Furthermore, comparable data on Acute Oral Toxicity in rats can be considered. Animal welfare aspects also justify the structural analogue approach.

  Stearic acid, esters with methyl α-D-glucoside is a reaction product of methyl glucoside with stearic acid, a linear saturated C18 fatty acid.

Isostearic acid, esters with methyl α-D-glucoside is a reaction product of methyl glucoside with the branched isostearic acid (100% UVCB substance).

Due to its esterification with the branched isostearic acid, the test substance is more hydrophobic than the Stearic acid, esters with methyl α-D-glucoside.

For Isostearic acid, esters with methyl α-D-glucoside and for Stearic acid, esters with methyl α-D-glucoside the reaction leads to a fatty acid ester in which the four OH-groups of glucose are partially esterified.

In the case of Isostearic acid, esters with methyl α-D-glucoside the product is composed of methylglucoside (4 %), methyl glucoside ester (approx. 83 % mono-, di-, and triester (mainly diester)) and of approx. 13 % free fatty acids. More than 90% of the fatty acids have a carbon number of 18, with some chain length distribution between C16 and C20. The main components are mono- and poly branched C18 fatty acids, in which the branching occurs mainly medium-chained, mostly methylenic, which accounts for its good biodegradability (Haase et al., 1989). However, a precise structure of isostearic acid does not exist.

 

Biodegradation studies performed on Isostearic acid, esters with methyl α-D-glucoside and Stearic acid, esters with methyl α-D-glucoside indicate a ready biodegradation within 28 days for both substances.

 

Comparing the results of acute oral toxicity both substances are practically non toxic to male and female Wistar rats. The oral LD50 males and females for both Isostearic acid, esters with methyl α-D-glucoside and Stearic acid, esters with methyl α-D-glucoside were > 2000 mg/kg bw.

 

Discussion

The short term aquatic toxicity results of Isostearic acid, esters with methyl α-D-glucoside are covering four trophic levels. The test substance could not be completely dissolved in the test medium at the loading rate of 100 mg/l because the water solubility was visually assessed to be less than 1 mg/l.  The most sensitive species was found to be the algae Pseudokirchnerella subcapitata with a 72 h ErC50 of > 100 mg/l (nominal). The 72 h NOEC for growth rate was 100mg/L, which was the maximum soluble concentration of the test substance. The percent growth inhibition compared to control was slightly reduced (8.5 %). The reduction was not considered to be of biological significance, as it was less than 10%. The total yield was inhibited by 36% when compared to the control. Hence, a 50% effect level could not be reached at the maximum soluble concentration of the test substance. There were no abnormalities noted.

 

The 48 h-EC50 of Daphnia magna was determined to be > 100 mg/l (nominal, limit test).

 

A reliable Short-term toxicity study to fish (reliability 2 "reliable with restrictions") according to OECD TG 203 with read-across substance Stearic acid, esters with methyl α-D-glucoside is available.

The 96 h acute toxicity of Leuciscus idus is >10000 mg test substance/l because the test substance was insoluble in water. The read across to Stearic acid, esters with methyl α-D-glucoside sufficiently covers this endpoint.

 

A 3 hour Activated Sludge, Respiration Inhibition Test according to OECD TG 209 with cultures of activated sludge of a predominantly domestic sewage treatment plant under static conditions indicated no significant inhibitory effects of the test item at 100 mg/l (3 h EC50 > 100 mg/l, nominal). The effects appear to be similar to those found for read across to Stearic acid, esters with methyl α-D-glucoside. The test performed with Pseudomonas putida according to DIN 38412 part 27 (Bacteria Respiration test, preliminary draft) showed no inhibition of oxygen consumption of Pseudomonas putida; therefore, the EC 50 is higher than 10000 mg/l.

Biodegradation studies performed on Isostearic acid, esters with methyl α-D-glucoside and Stearic acid, esters with methyl α-D-glucoside indicate a ready biodegradation within 28 days for both substances (see chapter 5.2).

No data on Long-term toxicity to fish is available. As the test substance is readily biodegradable (76 % in 28 days, see chapter 5.2.1) a Long-term toxicity to fish, as recommended in REACH Annex VIII 9.1.3, will not show any additional significant results. Presumably Isostearic acid, esters with methyl α-D-glucoside will be completely degraded in the environment. Besides this a Long-term toxicity test is difficult to perform because of the low water solubility and the difficulty of maintaining stable test concentrations. 

Comparing the results of valid acute oral toxicity studies both substances are practically non toxic to male and female Wistar rats. The rats were given a single oral dose at a concentration of 2000 mg/kg bw and observed for 14 days. The oral LD50 males and females for both Isostearic acid, esters with methyl α-D-glucoside and Stearic acid, esters with methyl α-D-glucoside were > 2000 mg/kg bw.

It is assumed that the metabolic pathways of both substances are similar. In animals and humans methyl branched fatty acids can be degraded by alpha oxidation. It is suggested that this metabolic pathway is also active in fish.

Short term toxicity to fish

In a 96-h acute toxicity study according to OECD TG 203, Leuciscus idus were exposed to Stearic acid, esters with methyl α-D-glucoside (according to producer information 100 % a. i.) at nominal concentrations of 0 (control) and 10000 mg test substance/l under static conditions. The test substance was pestled and was directly transferred into the dilution water without stirring or ultrasonic dispersion. The test substance was not dissolved in the test medium and no analytical control was performed. The test meets the validity criteria of the guideline.

The test substance Stearic acid, esters with methyl α-D-glucoside was non-toxic to Leuciscus idus. The 96-h LC50 is > 10000 mg test substance/l because the substance was not dissolved in water.

Short term toxicity to aquatic invertebrates

The 48–hr-acute toxicity of Isostearic acid, esters with methyl α-D-glucoside was investigated in a study conducted according to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test). Under static conditions Daphnia magma were exposed to control, reference substance (potassium dichromate) and the test chemical at a loading rate of 100 mg/l (limit test) for 48 h. Isostearic acid, esters with methyl α-D-glucoside could not be completely dissolved in the test medium at the loading rate tested because the water solubility was visually assessed to be less than 1 mg/l. No analytical control was performed. Immobilization was observed after 24 and 48 h.

The 24 h EC50 was > 100 mg/l (nominal, limit test)

Toxicity to aquatic algae and cyanobacteria

In a 72h acute toxicity study according to OECD guideline 201, the cultures of Pseudokirchnerella subcapitata NIVA CHL 1 were exposed to Isostearic acid, esters with methyl α-D-glucoside at a nominal concentration of 100 mg/L under static conditions in accordance to OECD Guideline 201. No analytical control was performed, and the test substance could not be completely dissolved in test medium at the loading rate tested.

The NOEC value was 100 mg/L. 72h-ErC50 for growth inhibition rate and the 72h-EyC50 for yield inhibition exceeded the maximum input concentration of 100 mg/L of the test substance. The % growth inhibition in the treated algal culture compared to the control was slightly reduced (8.5%). The reduction was not considered to be of biological significance as it was less than 10%. The total yield was inhibited by 36% when compared to the control. Hence, a 50% effect level could not be reached at the maximum input concentration of the test substance. There were no abnormalities noted. Results Synopsis: Test Organism: Pseudokirchnerella subcapitata NIVA CHL 1 Test Type: static 72 hr ErC50 for growth rate: >100 mg/L (nominal) 72 hr EyC50 for yield: >100 mg/L (nominal) 72 hr NOEC for growth rate: 100 mg/L (nominal)

Toxicity to microorganisms

In a 3 hour toxicity study conducted according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test) and EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test), the cultures of activated sludge of a predominantly domestic sewage treatment plant were exposed to Isostearic acid, esters with methyl α-D-glucoside at a nominal concentration of 100 mg/L under static conditions. No analytical control was performed.

There was no significant inhibitory effect of the test item at 100 mg/l; the deviations from the untreated controls were less than 15 %. The EC50 could not be calculated because Isostearic acid, esters with methyl α-D-glucoside proved to be non-toxic. Therefore the 3 h EC50 value based on inhibition of respiration was > 100 mg/L.

The value is supported by the 1 h EC 50 data from Stearic acid, esters with methyl α-D-glucoside. According to DIN 38412 part 27 (Bacteria Respiration test, preliminary draft) Pseudomonas putida was assessed by measuring the respiration rate after 1 hour at 0 and 10000 mg/l (nominal). No analytical control was performed. The 1 h EC 50 was higher than 10000 mg/l.