Sesame lignans enhance antioxidant activity of vitamin E in lipid peroxidation systems

The antioxidant properties of sesame lignans (sesamol, sesamin and sesamolin) were evaluated in comparison to tocols (alpha- and gamma-tocopherols and alpha-tocotrienol) and butylated hydroxytoluene (BHT) using the following in vitro lipid peroxidation systems: (i) rat liver microsomes and cumene hydroperoxide (CumOOH)/Fe2+-ADP-NADPH (enzymatic) or (ii) rat liver mitochondria and Fe2+-ascorbate (nonenzymatic) systems. Sesamol containing a free phenolic group inhibited lipid peroxidation in both the systems whereas sesamin and sesamolin having methylenedioxy groups were effective only in the microsomal system. Since detoxifying enzymes are localized in microsomes, the inhibitory effects of sesamin and sesamolin observed in the microsomal system may be attributed to their metabolites. However, the inhibitory effects of lignans were lower than tocols and BHT. Combination of individual lignans and tocopherols (alpha, gamma) or alpha-tocotrienol showed higher inhibitory effects than the sum of individual inhibitions in CumOOH and Fe2+-ascorbate systems suggesting synergistic interactions. The time course of CumOOH-mediated lipid peroxidation showed a lag period and a decreased rate of thiobarbituric acid reactive product formation in the presence of individual lignans in combination with alpha-tocopherol suggesting recycling of alpha-tocopherol.