EVIDENCE FOR THE FORMATION OF F-3-ISOPROSTANES DURING PEROXIDATION OFEICOSAPENTAENOIC ACID

8-Epi PGF(2 alpha), a potent vasocontrictor, is a specific product of non-enzymatic peroxidation of arachidonic acid. It seems likely that s imilar products could arise from other polyunsaturated fatty acids (PU FAs) and might be useful biomarkers of their peroxidation in vivo. Thi s was investigated using eicosapentaenoic acid (EPA). EPA liposomes (1 mg/ml PBS) were exposed at 37 degrees C to either 2,2'-azobis-(2-amid inopropane) dichloride (AAPH) or copper ions at final concentrations o f 1 mM and 10 mu M, respectively. Sample processing involved solid-pha se extraction on a C-18-followed by an NH2 cartridge. After conversion to pentafluorobenzyl ester/trimethylsilyl derivatives, F-3-isoprostan es 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 i on 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 oxidi sed by AAPH or by copper ions gave rise to a family of F-3-isoprostane s with 8-epi PCF3 alpha as a minor product. Formation of F-3-isoprosta nes correlated well with other indices of lipid peroxidation (hydroper oxides and thiobarbituric acid reactive substances). The possibility o f analysing specific lipid peroxidation products from individual fatty acids should facilitate nutritional and biomedical studies. (C) 1997 Academic Press.