Presence of cholesteryl ester hydroperoxide in human blood plasma.

An analytical method for quantitating the cholesteryl ester hydroperoxide and ubiquinols-9 and 10 in biological samples, especially plasma, was described. About 3 nM cholesteryl ester hydroperoxide, 20 nM ubiquinol-9, and 620 nM ubiquinol-10 were found in the hexane extract of healthy human plasma. Cholesteryl ester hydroperoxide was identified by its retention time, which was the same as that of standard hydroperoxide, its reduction with triphenylphosphine, and its splitting by cholesterol esterase. Since cholesteryl ester hydroperoxide was stable and no significant oxidation took place during the extraction procedure, cholesteryl ester hydroperoxide is most likely to be present in healthy human plasma.