Abstract
The oxidation of dihydrothiamine (DHT) with various metal ions, ascorbic acid and hydrogen peroxide was studied as a model experiment for thiamine formation from DHT under a physiological condition and the following results were observed. Only cupric ion among thirteen kinds of metal ions tested showed some activities for the oxidation of DHT in a solution at pH 7.3. The activity of cupric ion was seemed to be due to a catalytic action toward the oxidation of DHT by molecular oxygen, because more thiamine was produced from DHT at the presence of oxygen than nitrogen or carbon dioxide and thiamine formation decreased proportionally with the increase of cupric ion. The coexistence of ascorbic acid or hydrogen peroxide with cupric ion which appeared to rise such free radical as OH・did not cause any remarkable thiamine formation. On the other hands, the coexistence of cupric ion and dehydroascorbic acid showed apparently more formation of thiamine than cupric ion or dehydroascorbic acid alone. This suggests that if DHT exists in biological bodies, it would be easily converted to thiamine with combined action of dehydroascorbic acid and metal ions.
