Fatty acids, C14-22, 2-ethylhexyl esters, epoxidized

Endpoint summary

Description of key information

Epoxidized soybean oil (EC 232-391-0; CAS number 8013-07-8) is derived by epoxidation of soya bean oil. It is therefore considered to be a UVCB sub-type 1 material, since it is a modification of a substance of biological origin. Soya bean oil is a mixture of triglycerides (including linoleic [43-58%]; oleic [15-33%] and linolenic [5-12%] acids as the major fatty acid components. Epoxidation at some or all points of unsaturation (double bonds) in the fatty acid chains results in the epoxidized forms that are collectively known as epoxidized soybean oil (ESBO). Specifications, within the variations of possible ESBO combinations, are normally defined in terms of epoxidation number, oxirane oxygen content and iodine number. The first two being a reflection of the degree of epoxidation and the latter is a measure of the number of residual unsaturated double bonds. Given the nature of the epoxidation process, the final ESBO product may vary within the bounds of the degree of epoxidation and the mix of triglyceride content.

In its evaluation of epoxidized oils and derivatives the OECD SIDS conclusion indicates epoxidized fatty acid esters can be assumed to follow similar metabolic pathways to those of other vegetable oils since the primary constituents of the metabolic products are similar.

Based on structural, functional and metabolic similarities the primary epoxidized oils (incliding ESBO, ELO and ETP) can be considered within one functional category (see OECD SIDS for epoxidized oils and derivatives at  http://www.inchem.org/documents/sids/sids/Epoxidized-oils.pdf for further justification of category). Four epoxidized oils and derivatives form the Epoxidized Oils and Derivatives (EOD) Category based on structural and functional similarity.

Following metabolism, the alcohol metabolites from each material are a minor constituent of the metabolic products, and not produced in sufficient quantity to influence the toxicity profile of the EOD materials.

In mammalian species these EOD category materials are expected to be absorbed and metabolised in a similar fashion, resulting in the release of similar free epoxidized fatty acids and lesser substituted alcohols or glycerides. Lipase assists in the enzymatic breakdown and digestion of fat. Pancreatic lipase works at the oil/water interface since triglycerides are insoluble. During metabolism in the GI tract, pancreatic lipase preferentially hydrolyses triglycerides to release the free fatty acids from the SN-1 and SN-3 (terminal) positions of the glycerol backbone. The other products of metabolism are mono- and di-glycerides. These monoglycerides, diglycerides and fatty acids can then be absorbed.

Pancreatic lipase and other digestive enzymes have been shown to hydrolyse propylene glycol monoesters and diesters in a similar manner in vitro. The absorption, metabolism and hydrolysis of propylene glycol distearate (which is structurally similar to the EOD materials) were studied in rats using isotopically labelled compounds. The metabolic processes for propylene glycol esters were found to be similar to those of the glycerol esters. So, there is evidence that the propylene glycol esters of fatty acids are hydrolyzed to propylene glycol and fatty acids. The ETP structure is similar to that of the monoglycerides, formed from the metabolism of ELSO and ESBO. Further hydrolysis can also occur via carboxylesterase activity.

A relatively simple hydrolytic metabolic pathway is therefore proposed for ESBO involving enzymatic breakdown of the fatty acids and hydrolysis of alcohols or glycerides.

Read across to a study result from an investigation using a similar material is justified for members of the Epoxidised Oils and Derivatives group. Four epoxidised oils and esters (linseed, soybean,9-octadecanoate propylene glycol ester and 2-ethylhexyl tallate ester ETP). The C14-C22, 2-ethylhexylesters are listed as similar products on the market to ETP based on fatty acids from other naturally occurring fatty acids

This group of epoxies are identified as sharing common structural and functional similarities, recognised in an OECD SIDS review as a single category, and therefore justifying read-across between data for different members of the group. Consequently data sharing between ESBO epoxidised soybean oil, ELO epoxidised Linseed oil and ETP epoxidised 2ethylhexyl tallate and fatty acids, C14-C22, 2-ethylhexylesters, epoxidised is commonly utilised in the preparation of this dossier.

Read-across bridges are used for members of the EOD group where appropriate, is justified based on similar toxicity profiles and structural and functional similarities.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

In the absence of substance-specific data, default assumptions are made regarding the extent of absorption.