Ethyl 2,3-epoxy-3-phenylbutyrate

Endpoint summary

Additional information

The substance is not readily biodegradable, but considered as inherently biodegradable as determined in an OECD 301F ready test (53 % after 28 days). In addition, at the concentration used in the test (100 mg/L), it is not inhibitory to micro-organisms. Similar levels of degradation were observed in two additional biodegradation screening tests.

Assessment of hydrolytic stability was carried out according to OECD Guideline 111. The substance is considered to be hydrolytically unstable at pH4, 7 and 9 with half-lives ranging from 3.4 hours to 394.6 hours.

The substance does not meet the criterion for a rapidly hydrolysable substance (t½ is typically >12 hrs) and achieved biodegradation levels slightly below the pass criterion level of 60 % ThOD. Therefore the environmental hazard of potential breakdown products has been assessed.

Metabolites from the abiotic degradation study (hydrolysis as a function of pH) were tentatively identified by a combination of LC-UV, LC-MS and GC-MS analysis or tentatively assigned based on molecular mass and fragmentation. Four metabolites were identified: ethyl 2,3-dihydroxy-3-phenyl-3-phenylbutanoate (from hydrolytic opening of the epoxide ring), 3-methyl-3-phenyloxirane-2-carboxylic acid (product of ester hydrolysis), 2-phenylpropanal and acetophenone.

Breakdown products / metabolites from the process of biodegradation have been predicted using the CATALOGIC 301C v.07.08 model. Often, hydrolysis is the initial transformation process in biodegradation. Indeed, CATALOGIC predicted that the primary biodegradation product of ethyl 2,3-epoxy-3-phenylbutyrate would be ethyl 2,3-dihydroxy-3-phenyl-3-phenylbutanoate, a metabolite tentatively identified in the aforementioned hydrolysis study. Subsequent biodegradation breakdown products, which were predicted to be less degradable than the parent, were ethyl 2,3-dihydroxy-3-phenylbutanoate, 2,3-dihydroxy-3-phenylbutanoic acid, 2-hydroxy-2-phenylpropanoic acid and benzene.

Based on estimated log Kow values, all of the aforementioned metabolites are more polar than the parent substance and hence expected to be less toxic to the aquatic environment. Moreover for PBT/vPvB assessment purposes, both the parent and breakdown products have log Kow values which are below the B screening criterion of > 4.5. Thus no further assessment of the degradation products is warranted.

The registered substance is expected to have a low potential for bioaccumulation. The measured log Kow is < 3.0 and therefore testing for aquatic bioaccumulation has been waived.

The Koc for the substance was determined to be 550 according to an OECD 121 study.