抄録
Fee2+ and L-ascorbic acid induced oxidation of cholesterol was investigated in liposomes of egg yolk phosphatidylcholine (PC). Cholesterol 5, 6-epoxide, 7-hydroxycholesterol, 7-oxocholesterol, and cholestane-3, 5, 6-triol were detected as the oxidation products by gas chromatography, indicating that epoxidation and hydroperoxidation took place independently in cholesterol. Oxidation of cholesterol was accom-panied with oxidative loss of unsaturated fatty acid moiety of PC. When egg yolk PC was replaced by dimyristoyl-PC, little oxidation was observed in the cholesterol fraction. These results indicate that cholesterol oxidation depends on peroxidation of polyunsaturated fatty acids in liposomal phospholipids. α-Tocopherol incorporated into liposomes at a level of 1.0 mol% to egg yolk completely suppressed not only the loss of unsaturated fatty acid moiety, but also oxidation of cholesterol. α-Toco-pherol may inhibit cholesterol oxidation by suppressing phospholipid peroxidation. tert-Butyl hydroxytoluene, a synthetic antioxidant, was less effective against the oxidation of both PC and cholesterol.
