抄録
In the previous communication (Vitamins 23,364,1961), it was demonstrated that ps-dihydrothiamine (DHB_1) was much more stable than n-DHB_1 in its aqueous solution but the both isomers showed nearly the same stability when they were first dissolved in HCl and then made alkaline. Now ps-DHB_1 was isolated and identified by the same HCl-alkaline treatment of n-DHB_1. The stability and its decomposition products of n- or ps-DHB_1 in various kinds of solutions were revealed by paper partition chromatogaphy (butanol・acetic acid・H_2O 4 : 1 : 5) : The alcoholic solutions indicated one spot of DHB_1 (Rf 0.56) in both isomers, while the aqueous solution of n-DHB_1 showed three spots ; DHB_1,tris-(2-methyl-4-amino-5-pyrimidinyl-methyl)-hexahydro-S-triazine (I), and 5-hydroxy-3-mercapto-2-pentanone (II) but the aqueous solution of ps-DHB_1 indicated two spots ; DHB_1 and (I). The neutralized solution of n- or ps-DHB_1 which was first dissolved in NHCl, showed the presence of thiamine distinctly beside DHB_1,whereas a small portion of DHB_1 converted into thiamine, was always detected as a tailing spot by the alkaline-ferricyanide reagent in all kinds of the solutions. Decomposition of DHB_1 into (I) and (II) in its aqueous solution was prevented by the addition of (I) or both (I) and (II) ; in the latter case DHB_1 was kept as high as 80-100% even after standing for 48 hours.
