Influence of cholesterol on the kinetics of lipid autoxidation and on the antioxidative properties of α-tocopherol and quercetin

The autoxidation kinetics of triacylglycerols of sunflower oil (TGSO) in the presence of 10% cholesterol (Chol) at 80, 90 and 100 °C has been studied. The process was followed by monitoring the peroxide value and the formation of conjugated dienes. Cholesterol has been found to exhibit a prooxidative effect. During the oxidation of the mixture (TGSO/Chol), cholesterol peroxides were not registered. It is supposed that the initial amount of cholesterol peroxides formed decomposes to free radicals and that these radicals accelerate TGSO oxidation. A kinetic analysis of the antioxidative behavior of α-tocopherol and quercetin (2.9 x 10−4-17.8 × 10−4 M) in both TGSO and TGSO/Chol at 100 °C was performed. It was found that the effectiveness, strength, and activity of α-tocopherol are greater in TGSO/Chol than in TGSO, while these parameters for quercetin are practically the same in both lipid systems. The differences in the mechanism of action of α-tocopherol and quercetin are discussed.