Abstract
Thiamine solutions (about 5%) of different pH values between 5 and 12 were oxidized by ferricyanide or cyanogen bromide and their reaction products were separated by paper partition chromatography (butanol・H_2O) and detected by means of Dragendorff reagent or fluorecence. Ferricyanide-oxidation in the alkaline range showed always presence of thiamine-disulfide beside thiochrome which was detected much more distinctly after the solution had been made strongly alkaline. Cyanogen bromide to thiamine solution of pH values below 11.4 brought thiochrome as the major product and at pH between 10.7 and 11.6 cyanothiamine as the most distinct spot on paper partition chromatography, whereas at pH over 12 thiamine-anhydride and thiamine-disulfide were detected. Thiamine was first transformed into cyanothiamine in the alkaline medium by cyanogen bromide, then in the more alkaline solution cyanothiamine was decomposed to thiamine-anhydride or combined with an another molecule of thiamine forming thiamine-disulfide. In the quantitative estimation of thiamine by ferricyanide yield of thiochrome was 72-74% of the theoretical value and in nitrogen-saturated water, the yield was increased to 80-84% : Thus dissolved oxygen would have favored to form thiamine-disulfide instead of thiochrome.
