Evidence for the formation of F-3-isoprostanes during peroxidation of eicosapentaenoic acid

8-Epi PGF(2 alpha), a potent vasocontrictor, is a specific product of non-enzymatic peroxidation of arachidonic acid. It seems likely that similar products could arise from other polyunsaturated fatty acids (PUFAs) and might be useful biomarkers of their peroxidation in vivo. This was investigated using eicosapentaenoic acid (EPA). EPA liposomes (1 mg/ml PBS) were exposed at 37 degrees C to either 2,2'-azobis-(2-amidinopropane) dichloride (AAPH) or copper ions at final concentrations of 1 mM and 10 mu M, respectively. Sample processing involved solid-phase extraction on a C-18-followed by an NH2 cartridge. After conversion to pentafluorobenzyl ester/trimethylsilyl derivatives, F-3-isoprostanes were analysed by negative ion-chemical ionisation mass spectrometry (GC-MS/NICI) using tetradeuterated PGF(2 alpha) (PGF(2)-d(4)) as the internal standard. Quantitative analysis was carried out by selected ion monitoring of the carboxylated anion [M-180](-) at m/z 567 and 573 for the PGF(3)-like compounds and PGF(2)-d(4), respectively. EPA oxidised by AAPH or by copper ions gave rise to a family of F-3-isoprostanes with 8-epi PCF3 alpha as a minor product. Formation of F-3-isoprostanes correlated well with other indices of lipid peroxidation (hydroperoxides and thiobarbituric acid reactive substances). The possibility of analysing specific lipid peroxidation products from individual fatty acids should facilitate nutritional and biomedical studies. (C) 1997 Academic Press.