Abstract
Thiamine is sensitive to ultraviolet ray of the wave-length below 296mμ and it is decomposed into its pyrimidine-moiety (Okumura : Vitamins 24,158,1961). It was demonstrated that 1 mg% thiamine-HCl solutions of pH 1,4.5 and 6 are stable and remain unchanged after their 49 hours' irradiation by black light lamp having the maximal spectral energy at 365 mμ. whereas dibenzoylthiamine shows a gradual degradation on irradiation by black light lamp. Modified thiamine compounds of each 1 mg% (equivalent to thiamine-HCl) in alcohol indicate more or less rapid decomposition by the same procedure of irradiation. After irradiation for 6 hours, thiamine disulfide and its derivatives are decomposed to the extent over 60%, while S-benzoyl thiamine monophosphate, carbethoxythiamine and dicarbethoxythiamine are somewhat resistant to the irradiation, showing 60-80% recovery of the compounds. Thiamine, deoxythiamine and thiothiamine in alcohol are quite stable and only 5% of thiothiamine is decomposed after 6 hours' irradiation. 0.1% O-benzoylthiamine disulfide in alcohol is irradiated until 76% of the compound is destroyed and the reaction-mixture is fractionated by means of Amberlite IRC-50-resin column to an amine fraction, from which 2-methyl-4-amino-5-aminomethylpyrimidine is isolated as its picrate and identified.
