Effect of lipid peroxidation products and antioxidants on the formation of probucol radical in low density lipoproteins.

Effects of antioxidants and products of lipid peroxidation on hemin-induced formation of probucol radical in low density lipoproteins (LDL) from human plasma were studied by EPR-spectroscopy. Suppression of lipid peroxidation in LDL by probucol and other antioxidants (ascorbate, 6-O-palmitoylascorbate, and ubiquinol-10) prevents the formation of probucol radical. However, ubiquinol-10 stimulates the formation of probucol radical during advanced stages of LDL oxidation. Because the concentration of probucol radical depends on lipid hydroperoxide contents in LDL, the interaction of lipid hydroperoxides with hemin can result in the formation of probucol-oxidizing radical intermediates and ubiquinol-10 is a mediator of this process.