Effects of interaction between α-tocopherol, oryzanol, and phytosterol on the antiradical activity against DPPH radical

Natural antioxidants are a complex system of molecules that interact to scavenge free radicals and often exist as minor compounds that are important for the nutritional benefits and functions of plant oils. In this study, the scavenging activity of α-tocopherol in the presence of γ-oryzanol and phytosterol in a radical medium was investigated using the 2,2-diphenyl-a-picrylhydrazyl assay. The compounds α-tocopherol, γ-oryzanol, and phytosterol were added to the reaction system separately and together at a range of concentrations. Interaction of the antioxidants was calculated by comparing the experimental and theoretical free radical scavenging activities. The results revealed an antagonistic interaction between α-tocopherol and γ-oryzanol, as well as between α-tocopherol and phytosterol at all concentrations investigated. Additionally, formation of hydrogen bonds and inhibition of α-tocopherol regeneration played important roles for the antagonistic interaction in the polar system. These findings provided insights that may be of interest for oil processing to ensure that the contents of the minor compounds are in a suitable range.