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The genetic toxicity of sorbitan caprylate was derived from experimental studies and analogue approaches using sorbitan stearate as source chemical.

 

The analogue approach using sorbitan stearate as source chemical is justified:

Both chemicals are of comparable structures with minor deviations and can be characterized as an ester of sorbitan and a fatty acid. Compared to the source chemical, the target chemical has a shorter alkyl chains that affect its physicochemical properties. But based on the kinetic / metabolic investigations on both chemicals, the length of the alkyl chain is not considered to have significant impact on the metabolic pathway or toxicological mode of action. Oral gavage studies in rats administered C14 labeled sorbitan stearate in oil solutions have demonstrated that about 90% of the substance was absorbed and hydrolyzed to stearic acid and sorbitan. The metabolic fate of sorbitan caprylate was investigated using a lipase assay. The hydrolysis mediated by porcine pancreas lipase was quantitatively determined. The target chemical sorbitan caprylate is proved to be hydrolyzed and caprylic acid was formed . These findings suggest that metabolism of the sorbitan occur initially via enzymatic hydrolysis, leading to sorbitan and the corresponding natural acids.

Based on the above mentioned information, it is reasonable to consider that these two substances are comparable in their metabolic fate and thereby toxicological profiles. Hence, the source chemical is considered as “suitable with interpretation” analog.

According to the available toxicity studies, the findings are also comparable for target and source chemicals:

·        The findings in acute toxicity studies are comparable. Both chemicals are of no acute toxicity.

·        The findings in subacute dose toxicity studies are comparable. No treatment effects were observed in 28-day repeated toxicity studies in Wistar rats. The same NOEL of 1000 mg/kg bw/d was derived for both chemicals.

·        The findings in genetic toxicity are comparable. Both chemicals did not induce gene mutations in Ames tests, but induced structural chromosomal aberrations in cell lines of Chinese Hamster.

·        The findings in reproduction / developmental toxicity studies are comparable.

 

Two Ames tests are available on sorbitan caprylate and its source chemical sorbitan stearate. Both chemicals were investigated with strains TA 1535, TA 1537, TA 98, TA 100, and WP2 uvrA. No substantial in crease in revertant colony numbers of any tested stains was observed following the treatment with test item at any dose level, neither in the presence nor absence of metabolic activation (S9 mix).

 

In a mammalian cell gene mutation assay (HPRT locus),V79 cells cultured in vitro were exposed to sorbitan caprylate suspended in DMSO at several levels up to cytotoxic concentrations. The study was performed according to OECD guideline 473. There was no evidence of a concentration related positive response of induced mutant colonies over background, either with or without the metabolic activation (S9 mix). Therefore, the test item sorbitan caprylate was considered to be non-mutagenic in the HPRT locus using V79 cells of the Chinese Hamster.

 

Sorbitan caprylate was assessed in the in vivo micronucleus assay for its potential to induce micronuclei in polychromatic erythrocytes (PCE) in the bone marrow of the mouse. In comparison to the corresponding vehicle controls there was no statistically significant or biologically relevant enhancement in the frequency of the detected micronuclei at any preparation interval and dose level after administration of the test item. The mean values of micronuclei observed after treatment with sorbitan caprylate were below or near to the value of the vehicle control group and all within the historical vehicle control data range. A level of 40 mg/kg b.w. cyclophosphamide administered orally was used as positive control which showed a statistically significant increase of induced micronucleus frequency. Based on the experimental results, it can be stated that during the study described and under the experimental conditions reported, the test item sorbiran caprylate did not induce micronuclei as determined by the micronucleus test in the bone marrow cells of the mouse.

The source chemical sorbitan stearate was also assessed in the in vivo micronucleus assay in the bone marrow of the mouse. Sorbitan stearate was administered in male mice by gavage once per day for 2 days. Water was used as negative control and CP was used as positive control. No effect of micronuclei induction was observed in the groups treated with sorbitan stearate and significant effects were observed in the postive control group. Therefore the source chemical sorbitan stearate also did not induce clastogen effect in the bone marrow cells of mice.

 

Three in vitro mammalian chromosome aberration tests were performed to investigate the genotoxic potential of sorbitan caprylate and its analogue sorbitan stearate, using Chinese Hamster V79 and CHO K1 cells (for sorbitan caprylate), and CHL/IU cells (for sorbitan stearate), respectively. Although in the test using CHO K1 cell line, the substance sorbitan caprylate is considered as non-clastogenic, the results of studies using V79 and CHL/IU cells indicated that both target chemical sorbitan caprylate and source chemical sorbitan stearate induced structural chromosomal aberration under the described experimental conditions. The different results from the studies with V79 cells and CHO K1 cells are considered due to biological difference of the two cell lines and the tested concentrations in the two studies. However, the observed clastogenic activity in chromosome aberration tests with V79 and CHL/IU cells is considered to be of limited relevance with respect that a) the observed effect might have been due to the osmotic stress; b) negative results were obtained in in-vivo study; c) structurally related substance sorbitan stearate was clastogenic in in-vitro chromosome aberration test as well but not carcinogenic in life-time bioassay. Furthermore, the induction of chromosomal aberration was considered to be due to the metabolized fatty acids in the in-vitro system. The in-vitro metabolism of fatty acids occur mainly via omega-oxidation instead of beta-oxidation which takes place predominantly in-vivo (Kam et al., 1976; Lim et al., 2010; Wangers et al., 2011). Duringω-oxidation a hydroxyl group is induced on to theω-carbon and further concerted by alcohol dehydrogenase (ADH) to the respective reactive aldehyde (Simon et al., 2002). Aldehydes are known to also potentially induce chromosome aberrations in-vitro. Saturated fatty acids can also be converted in-vitro by desaturase also to unsaturated fatty acid(s) (St John et al., 1991), which also may induce chromosome aberrations. But due to differences in the in-vivo and in-vitro metabolism, no biological relevance is attributable to the positive findings in the in-vitro cytogenetic assay. (Literatures cited are listed in the attached “Assessment of the validity of the analogue approach used for hazard assessment of sorbitan caprylate”)

Overall, it can be concluded from the data available for sorbitan caprylate and its structural analogue sorbitan stearate that no mutagenicity and genotoxicity are caused by sorbitan caprylate and therefore classification for this end point is not warranted.


Short description of key information:
in vitro:
-Ames test: negative (one study on sorbitan caprylate, one study on the read-across supporting substance sobitan stearate)
-mammalian cell gene mutation assay: negative (one study on sortbitan caprylate)
-chromosome aberration test: positive (one study on sorbitan caprylate, one study on the read-across supporting substance sorbian stearate)
-chromosome aberration test: negative (one study on sorbitan caprylate)

in vivo:
-micronucleus test in mice: negative (one study on sorbitan caprylate)
-micronucleus test in mice: negative (one study on read-across supporting substance sorbitan stearate)

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the available data, sorbitan caprylate is considere to be not genotoxic and therefore classification for this end point is not warranted according to the criteria laid down in the EU Dangerous Substances Directive (67/548/EEC) and in the EU Classification Labelling and Packaging Regulation (1272/2008/EC).

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