Trans fatty acids: chemical synthesis of eicosapentaenoic acid isomers and detection in rats fed a deodorized fish oil diet.

Eicosapentaenoic acid (EPA) is a polyunsaturated fatty acid present in fish oils used for omega-3 enriched diets. The natural cis double bond geometry can be transformed to the trans configuration during the deodorization process utilized in the food industry. The analytical discrimination of the possible five monotrans regioisomers represents a limiting step for the recognition and structure-activity relationship in connection with the harmful effects of trans fatty acids in health. We carried out a dual synthetic strategy, providing new access to monotrans EPA isomers and valuable information on GC and NMR characteristics for further applications in metabolomics and lipidomics. This small library was used as an analytical reference for isomer determination in deodorized fish oils and the follow-up of rats fed fish oil diets, evidencing for the first time that monotrans EPA isomers are incorporated in liver mitochondrial membranes after dietary intake.