Differential Inhibitory Effect of alpha-, beta-, gamma-, and delta-Tocopherols on the Metal-Induced Oxidation of Cholesterol in Unilamellar Phospholipid-Cholesterol Liposomes

摘要

Cholesterol oxidation products (COPs) are present in biological tissues and in foods. The inhibitory effect of antioxidants, such as tocopherols, on COPs formation has been only partially investigated. The antioxi-dant effect of dl alpha-, dl beta-, dl gamma-, and dl-delta tocopherol on the metal-induced oxidation of phos-phatidylcholine (PC): cholesterol liposomes was assayed. Formation during liposome oxidation of six different COPs was monitored by gas chromatography. dl alpha-, and dl gamma-tocopherol show good inhibitory effect against PC-fatty acid oxidation and also on COPs formation. dl delta-Tocopherol is less effective than the alpha-ami gamma-homologous, beta-tocopherol being unable to prevent PC and cholesterol oxidation. dl alpha-, and dl gamma-Tocopherol are more effective to prevent the oxidation of the lateral chain of cholesterol molecule. At the highest tocopherol concentration assayed, dl alpha-tocopherol shows prooxidant effect, enhancing liposo-mal oxidation and COPs formation. It is concluded that the tocopherols assayed can inhibit cholesterol oxidation hut to a different degree.