Headspace gas chromatography to determine human low density lipoprotein oxidation

We previously described a rapid headspace gas chromatographic method for the determination of hexanal, an important decomposition product of n-6 polyunsaturated fatty acid (PUFA) peroxidation in rat liver samples and human red blood cell membranes. This method was applied to the measurement of Cu2+ catalyzed-oxidation of freshly prepared human low density lipoproteins (LDL) from 10 healthy adult volunteers. A twofold variation in oxidative susceptibility was found by this assay for hexanal and other volatiles. Hexanal values correlated significantly (P < 0.05) with total polyunsaturated fatty acid (PUFA), 18:2 and n-6 PUFA contents of LDL; but poorly with 20:4 and with vitamin E. Therefore, in addition to alpha-tocopherol, other endogenous antioxidants and factors may contribute to LDL's resistance to oxidation. This simple, rapid and sensitive method for oxidative susceptibility provides a useful component in the analysis of the prooxidant/antioxidant status of biological samples. The method is used routinely in our laboratories to determine specific peroxidation products of n-6 and n-3 PUFA.