作者:Kazuo Mukai、Yoshiko Watanabe、Yuichi Uemoto、Kazuhiko Ishizu
DOI:10.1246/bcsj.59.3113
日期:1986.10
It was observed by ESR measurement that the oxidation of α-, β-, γ-, and δ-tocopherols (vitamin E) with a stable phenoxyl radical in benzene immediately gives corresponding tocopheroxyl radicals. The rates of reaction of α-, β-, γ-, and δ-tocopherols with the stable phenoxyl radical in ethanol solution have been determined spectrophotometrically using stopped-flow technique, as a model reaction of tocopherols with unstable free radicals (ROO·, RO·, and HO·) in biological systems. The second-order rate constants obtained are (5.12±0.36)×103 (α-Toc), (2.24±0.04)×103 (β-Toc), (2.42±0.16)×103 (γ-Toc), and (0.51±0.01)×103 (δ-Toc), M−1 s−1 in ethanol at 25.0 °C. The relative rates agree well with those obtained from studies of the reactivities of tocopherols toward poly(styrylperoxyl) and galvinoxyl radicals by O2 consumption and by ESR method, respectively. The results suggest that the relative reactivities, that is, relative antioxidant activities of tocopherols do not depend on the kinds of unstable free radicals reacted.
通过 ESR 测量观察到,α-、β-、γ- 和 δ-生育酚(维生素 E)在苯中与稳定的苯氧自由基发生氧化反应,立即产生相应的生育酚氧自由基。作为生育酚与生物系统中不稳定自由基(ROO-、RO- 和 HO-)反应的模型,使用停流技术分光光度法测定了 α-、β-、γ- 和 δ-生育酚与乙醇溶液中稳定苯氧自由基的反应速率。在 25.0 °C 的乙醇中,得到的二阶速率常数分别为 (5.12±0.36)×103 (α-Toc), (2.24±0.04)×103 (β-Toc), (2.42±0.16)×103 (γ-Toc), 和 (0.51±0.01)×103 (δ-Toc), M-1 s-1。这些相对速率与通过消耗 O2 和 ESR 法研究生育酚对聚(苯乙烯基过氧乙酸)和乙烯基过氧乙酸自由基的反应活性所获得的速率非常吻合。结果表明,生育酚的相对反应活性(即相对抗氧化活性)并不取决于发生反应的不稳定自由基的种类。