Stereospecific analysis of γ-linolenic acid-rich triacylglycerols by HPLC

Abstract

A simple method is described for determining the positional distribution of fatty acids in γ linolenic acid-rich triacylglycerols (TGs). The oils from the filamentous fungus Mucor arcmelloides and its variant were analyzed for this purpose. The procedure involved the preparation of SH-l,2(2,3)-diacylglycerols (DGs) by the partial deacylation of TGs with a Grignard reagent, the preparation of 3,5-dinitrophenylurethane (DNPU) derivatives of the DGs, the resolution of the enantiomeric sn-1,2- and sn-2,3-DGs by chiral-phase HPLC, the resolution of molecular species of DGs in each enantiomer group by reversed-phase HPLC, and the determination of the fatty acid composition by gas-liquid chromatography. The positional distributions of the fatty acids were calculated from the fatty acid compositions of the original TGs and the enantiomeric sn-1,2- and sn-2,3-DGs. The results demonstrated the preferential association of γ-linolenic acid to the sn-3 position, followed by the sn-1 position, and then the sn-2 position in both oils.