The effect of various reducing compounds on the thiamine activity of S-benzoylthiamine O-monophosphate.

It has been shown in the previous paper (1) that S-benzoyl derivatives of thiamine, e. g., S-benzoylthiamine O-monophosphate (BTP) and S-benzoylthiamine (SBT), have seemingly thiamine activity on Lactobacillus ferinenti, but they are not active per se; it is due to the production of thiamine-active compounds by de-S-benzoyla tion. It seems to be of interest to clarify the mechanism of debenzoylation. Thiamine disulfide derivatives are known to be reduced to thiamine by cysteine (2). Honda (3) demonstrated using thiamine allyl disulfide (TAD) that it was reduced to thiamine by the reducing agents other than cysteine, e.g., sodium thiosulfate or sodium hydrosulfite. In order to investigate whether L-cysteine has the reducing activity to the S-benzoyl derivatives of thiamine, various reducing agents other than cysteine were added to BTMP and the activity for growth of L. fermenti and thiochrome reaction were studied.