Antioxidant effect of β-carotene on lipid peroxidation and synergism with tocopherol in an emulsified linoleic acid model system

The antioxidant effect of β-carotene was investigated in an emulsified linoleic acid model system with or without exposure to light. The effect of tocopherol on the antioxidant action of β-carotene was also investigated. The antioxidant effect of β-carotene was significant, and synergistically increased by the addition of rac α-tocopherol, in the dark but not in the light. It was confirmed that superoxide anions (O2−) and hydrogen peroxide (H2O2) were formed during the light exposure, and that their formation could be significantly inhibited by the addition of tryptophan or mannitol, scavenger of hydroxyl radicals. These results strongly suggest direct participation of hydroxyl radicals, formed via the Haber-Weiss reaction, in the emulsified linoleic acid model system, with β-carotene inhibition in the dark but an increase in the light. Regarding the mechanism of the antioxidant effect of β-carotene, when β-carotene is oxidized, the hydroperoxide in the acts as an electron acceptor and the hydroperoxide itself then decomposes.