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[27] Tocopherone and epoxytocopherone products of vitamin E oxidation

1994; Academic Press; Linguagem: Inglês

10.1016/0076-6879(94)34098-6

1557-7988

D.C. Liebler,

Vitamin C and Antioxidants Research

α-Tocopherol (vitamin E) is the principal chain-breaking antioxidant in most biological membranes and in lipoproteins. As a chain-breaking antioxidant, it reacts primarily with peroxyl radicals, which are the principal chain-carrying species in biological lipid peroxidation. The reaction yields the tocopheroxyl radical, a resonance-stabilized phenoxyl radical that does not readily propagate radical chain reactions. Reduction of tocopheroxyl radical to α-tocopherol by biochemical reductants may complete a one-electron redox cycle, which accounts for the antioxidant synergism between α-tocopherol and other antioxidants. The tocopheroxyl radical molecules that do not complete redox cycles may react with a second peroxyl radical to form other products. In consuming a second peroxyl radical, the reaction contributes to the antioxidant effects of α-tocopherol. The reaction removes tocopheroxyl radical from the system, leads to α-tocopherol oxidative turnover, and may yield marker products for α-tocopherol function in biological systems. This chapter describes the methods to characterize and analyze 8a-substituted tocopherones and epoxytocopherones, which are the principal products formed by peroxyl radical-mediated oxidations of α-tocopherol.