Differential inhibitory effect of alpha-, beta-, gamma-, and delta-tocopherols on the metal-induced oxidation of cholesterol in unilamellar phospholipid-cholesterol liposomes

Abstract

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 antioxidant effect of dl alpha-, dl beta-, dl gamma-, and dl-delta tocopherol on the metal-induced oxidation of phosphatidylcholine (PC): cholesterol liposomes was assayed. Formation during liposome oxidation of six different CON 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- and 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 liposomal oxidation and CON formation. It is concluded that the tocopherols assayed can inhibit cholesterol oxidation but to a different degree.