Gas chromatographic-mass spectrometric identification of four triene monoepoxides of arachidonic acid in human plasma

Abstract

Four triene monoepoxides of arachidonic acid have been identified as endogenous components of human plasma, the epoxy groups being in the 5,6-, 8,9-, 11,12- and 14,15-positions. Prior to trimethylsilylation and gas chromatographic-mass spectrometric analysis, both the epoxy and ester functions were reduced to hydroxy groups and the double bonds were hydrogenated catalytically. Saturation of the double bonds gave diagnostic spectra that were suitable for elucidating the position of the epoxy group. The shift in the fragmentation of a deuteriated sample verified the presence of the intact epoxides prior to chemical reduction. The presence of the double bonds in the epoxy molecules was demonstrated by reduction using homogeneous catalysis with tris(triphenylphosphine)rhodium(I) chloride and deuterium.