Headspace gas chromatography to determine human low density lipoprotein oxidation

Abstract

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 α‐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.