Reactions between phosphorylated thiamines and tannic acid as followed by difference spectroscopy.

Caffeic acid, catechin, chlorogenic acid, hydroquinone (also benzoquinone) and tannic acid were used to react with thiamine and the ultraviolet-visible difference spectra were recorded. The time-course of the thiamine-polyphenol interactions was studied by following the difference absorbance change with time. The rate of reaction as determined by difference spectroscopy was the same as that found by chemical assay. The spectroscopic method showed that thiamine, thiamine monophosphate and thiamine diphosphate reaction rate with tannic acid followed the order thiamine greater than thiamine monophosphate greater than thiamine diphosphate up to pH 7.4.