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.

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We compared the contents of the eight B-group vitamins in the liver, kidney, blood and urine of rats fed a 20% casein -1.0% AIN-93 vitamin mixture (recommended addition of AIN-93 vitamin mixture) diet or 20% casein-0.3% AIN-93 vitamin mixture (tentative minimal requirement) diet. There were no differences of body weight gains, food intakes, and liver and kidney weights between the two groups. Of the liver B-group vitamin contents, only the vitamin B_1 content was lower in the group fed the 0.3% vitamin mixture diet than in the group fed the 1.0% vitamin mixture diet. The contents of other seven vitamins were not different even though the intakes of the vitamins were decreased to be 1/3.3. In the kidney, the vitamins that were decreased by administering the 0.3% vitamin mixture diet were only two vitamins, B_1 and B_<12>. In the blood, the vitamin B_1, vitamin B_6, and folate concentrations were decreased by administering the 0.3% vitamin mixture diet. In the urine, seven kinds of the B-group vitamins except vitamin B_<12> were decreased by administering the 0.3% vitamin mixture diet.

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