抄録
Examinations were made on the stabilities of thiamine (B_1) and three ethoxycarbonyl-thiamines (3mM) in aqueous ethanol of different concentrations ranging from 20 to 99.5% (v/v) at 100℃ in ampules in comparison with those in aqueous solution. Each of the compounds was degraded by a pseudo first-order reaction, regardless of the presence of ethanol. A decrease in stability of B_1 was found by increasing the ethanol concentration, the rate showing a maximum in 80% ethanol. O-Ethoxycarbonylthiamine (OCET) in aqueous ethanol was decomposed showing a maximum rate in 60〜80% ethanol, where B_1 was not given even after 10 hours, while in the aqueous solution, the amount of B_1 produced from OCET was 1.7%. An increase in stability of S-ethoxycarbonylthiamine was found in proportion to the increase in ethanol concentration. The decomposition rate constant in 99.5% ethanol was less than 1/20 of the rate in aqueous solution. The degradation rate of O, S-bis (ethoxycarbonyl) thiamine in aqueous solution was little influenced by the addition of ethanol, but the percentages of the formation of thiochrome-reaction-positive compounds decreased with the increase of ethanol concentration.
