A simple and sensitive method in using the ratios of cholesteryl ester molecular species as indexes of oxidative stress in plasma and lipoprotein fractions

To develop a simpler method for lipid peroxidation which may replace the classic gold standard of measuring the loss of polyunsaturated fatty acids, we investigated the use of ratios of molecular species of neutral lipids (MSNL) separated by gas chromatography in a single step. We sub-fractionated lipoproteins and subjected each to oxidation. Among different combinations of ratios of MSNL, we found that the ratios of cholesteryl esters (CE) containing C20/C16 (R1) and C18/C16 (R2) decreased most rapidly with increasing Cu+2 concentration and with increasing oxidation time, for all lipoproteins. We suggest that these two CE ratios can be used as oxidative indexes for all lipoproteins and thus for intact plasma. Experimental evidence showed that the oxidative index of whole plasma is the weighted average index of its lipoproteins. This method was validated with thiobarbituric acid method. Normal healthy asymptomatic males had R1 value 0.496±0.130, and R2 4.674±0.848, and females had R1 0.535±0.117 and R2 4.569±0.733 with no significant gender differences. Both ratios showed low variabilities within each individual. The method was tested to be feasible in monitoring vitamin E supplementation study. This CE-ratio method is concentration independent. It is simple, rapid, and highly reproducible, and, suitable for screening plasma on large scale.