Stearic acid, esters with methyl α-D-glucoside

Endpoint summary

Additional information

Justification for read across

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

Stearic acid, esters with methyl α-D-glucoside is a reaction product of Methyl glucoside with Stearic acid, a linear saturated mainly C18 fatty acid whereas for Isostearic acid, esters with methyl α-D- glucoside the branched Isostearic acid is used. Composition of chain length is very similar; 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 of Isostearic acid are mono- and poly branched C18 fatty acids, in which the branching occurs mainly medium-chained, mostly methylenic, which accounts for its good biodegradability. However, a defined structure of isostearic acid does not exist.

The reaction leads to a fatty acid ester in which the four OH-groups of glucose are partially esterified.

Due to its esterification with the branched Isostearic acid, isostearate is more hydrophobic than the sesquistearate.

Stearic acid, esters with methyl α-D-glucoside is composed of Methylglucoside (2.4 %), Methyl glucoside ester (approx. 78 % mono-, di-, tri-, and tetraester (mainly di, and triester)) and of approx. 19 % free fatty acids. Whereas Isostearic acid, esters with methyl α-D-glucoside is composed of Methylglucoside (4 %), Methyl glucoside ester (approx. 83 % mono-, di-, and triester (mainly diester)) and of approx. 13 % free fatty acids.

Likewise intrinsic toxicological properties of Stearic acid, esters with methyl α-D-glucoside and Isostearic acid, esters with methyl α-D-glucoside are proven for acute oral toxicity, skin and eye irritation, skin sensitization and genmutation in bacteria. The read-across substance Isostearic acid, esters with methyl α-D-glucoside, containing branched chains, is considered to be more critical in its toxicological impacts and can be understood as a worst case in this analogue approach. However, no intrinsic toxicological property leading to an intrinsic health hazard could be identified for the Isostearic acid, esters with methyl α-D-glucoside.

In conclusion this structural analogue approach is scientifically justified by close similarities of structural aspects and physico-chemical properties and finally the comparable harmless toxicological profile of both substances.

Discussion

The short term aquatic toxicity results of Stearic acid, esters with methyl α-D-glucoside are covering four trophic levels.

 

Short-term toxicity study to fish performed according to OECD TG 203 in 1990 and test to microorganisms performed according to DIN 38412 part 27 with Stearic acid, esters with methyl α-D-glucoside are available.There are reliable short-term toxicity studies to aquatic invertebrates, algae and cyanobacteria and microorganisms (reliability 2) with read-across substance Isostearic acid, esters with methyl α-D-glucoside.

 

The most sensitive species was found to be the algae Pseudokirchnerella subcapitata with a 72 h ErC50 of > 100 mg/L (nominal) in a study performed to the read across substance Isostearic acid, esters with methyl α-D-glucoside.

 

The 48 h-EC50 of Daphina magna was determined to be > 100 mg/L (nominal, limit test) in a study performed to the read across substance Isostearic acid, esters with methyl α-D-glucoside.

 

In the short-term toxicity study to fish with Stearic acid, esters with methyl α-D-glucoside is available, the 96 h acute toxicity of Leuciscus idus is >10000 mg/L, the test substance was not completely dissolved in water.

 

In the test performed according to DIN 38412 part 27 (Bacteria Respiration test, preliminary draft) no inhibition of oxygen consumption of Pseudomonas putida was observed, therefore the EC50 is higher than 10000 mg/L.

The effects are likely to be similar to those found for read across substance Isostearic acid, esters with methyl α-D-glucoside. In an Activated Sludge, Respiration Inhibition Test according to OECD TG 209 no significant inhibitory effects of Isostearic acid, esters with methyl α-D-glucoside were observed at 100 mg/l (3 h-EC50 > 100 mg/L, nominal).

 

No data on long-term toxicity to fish is available. As the test substance is readily biodegradable (89% in 28 days, see chapter 5.2.1) a long-term toxicity study to fish, as recommended in REACH Annex VIII 9.1.3, will not deliver any additional information. Presumably Stearic 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.

 

Additionally, no toxic effects were observed in vivo studies performed to other species. Both substances are proved to be practically non toxic to Wistar rats in oral test. The oral LD50 males and females for both Stearic acid, esters with methyl α-D-glucoside and Isostearic acid, esters with methyl α-D-glucoside were > 2000 mg/kg bw, showing coherent trends in their toxicological properties.

It is assumed that the metabolic pathways of both substances are similar. In animal and human methyl branched fatty acids can be degraded by alpha oxidation. Possibly the metabolic pathways of rat can be transferred to fish.

 

No data on sediment or terrestrial toxicity is available.

 

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.
Stearic acid, esters with methyl α-D-glucoside was non-toxic to Leuciscus idus. The 96-h LC₅₀is > 10000 mg/L the test substance was not completely dissolved in water

 

Short term toxicity to aquatic invertebrates

The 48–hr-acute toxicity study with Isostearic acid, esters with methyl α-D-glucoside conducted according to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) is available. Under static conditions Daphnia magna 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-EC₅₀was > 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, which was above the solubility limit of the test substance. 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 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 ErC₅₀for growth rate:  >100mg/L  (nominal)

72 hr EyC₅₀for yield: >100mg/L (nominal)

72 hr NOEC for growth rate: 100mg/L (nominal)

 

 

Toxicity to microorganisms

The toxic effects of Stearic acid, esters with methyl α-D-glucoside (according to producer infromation 100% a.i.) on Pseudomonas putida according to DIN 38412 part 27 (Bacteria Respiration test, preliminary draft) was assessed by measuring the respiration rate after 1 hour at 0 and 10000 mg/L (nominal). No analytical control was performed. Based on the study results Stearic acid, esters with methyl α-D-glucoside showed no inhibition of oxygen consumption of Pseudomonas putida. Therefore, the 1 h-EC50 of the test substance is higher than 10000 mg/L.

The effects are likely to be similar to those found 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.