Mixed tocopherols have a stronger inhibitory effect on lipid peroxidation than alpha-tocopherol alone

Intake of vitamin E with food (mixed tocopherols) has been found to counteract the development of atherosclerotic cardiovascular disease, whereas intake of large amounts of pure alpha-tocopherol has shown only a slight or no effect in clinical studies. This study was designed to investigate the effects of alpha-tocopherol alone and a mixed tocopherol preparation (gamma-, delta-, and alpha-tocopherol) on hydrogen peroxide-induced lipid peroxidation in human erythrocytes. Erythrocytes were incubated with different concentrations of alpha-tocopherol or mixed tocopherols and then exposed to hydrogen peroxide. Tocopherol levels and malondialdehyde-thiobarbituric acid-reactive substances were determined by high-performance liquid chromatography and fatty acids by gas chromatography. Incubation of erythrocytes with tocopherols (30-120 microM) increased the tocopherol level in a concentration-dependent manner. The uptake of gamma- and delta-tocopherols was much higher than that of alpha-tocopherol. Hydrogen peroxide strongly increased lipid peroxidation and decreased polyunsaturated fatty acids in erythrocytes. Both alpha-tocopherol and the tocopherol mixture protected the cells from lipid peroxidation, the mixture being much more potent than alpha-tocopherol alone. This study indicates that a mixture of tocopherols has a stronger inhibitory effect on lipid peroxidation induced in human erythrocytes than alpha-tocopherol alone, due to higher uptake of gamma- and delta-tocopherol in the cells.