ユビキノールによるビタミンEの再生反応に及ぼす金属塩の効果とメカニズム

概要

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A kinetic study of regeneration reaction of α-tocopherol (α-TocH) by ubiquinol-10 has been performed in the presence of alkali and alkaline earth metal salts in methanol and acetonitrile solutions. Notable effects of metal cations on the UV-Vis absorption spectrum of α-tocopheroxyl (α-Toc・) radical were observed in aprotic acetonitrile solution, suggesting a complex formation between α-Toc・ and metal cations. On the other hand, effects of metal cations were negligible in protic methanol, suggesting that the complex formation between α-Toc・ and metal cations is hindered by the hydrogen bond between α-Toc・ and methanol molecules. The second-order rate constants (k_r) for the reaction of α-Toc・ with ubiquinol-10 increased and decreased notably with increasing concentrations of metal salts in methanol and acetonitrile, respectively. The difference in the reaction mechanism in methanol and acetonitrile was discussed based on the results obtained. High concentrations of alkali and alkaline earth metal salts coexist with α-TocH and ubiquinol-10 in plasma, blood and many tissues, suggesting the contribution of the metal salts to the above regeneration reaction in biological systems.
2012-06-25