Differences in Thiochrome Fluorescence Produced by Thiamine and Its Mono-, Di-, and Triphosphate Esters.

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Abstract
Equimolar amounts of thiamine and its mono-, di- and triphosphate esters, when oxidized with potassium hexacyanoferrate(III) in an alkaline medium, produced unequal intensities of thiochrome fluorescence. These differences were less pronounced if the oxidation medium contained ethanol. Assuming that the phosphate groups do not increase the fluoresence, then in 50% ethanol (vol/vol); 74% of thiamine and thiamine monophosphate, 85% of thamine diphosphate and 93% of thiamine triphosphate are converted to thiochrome. The differences observed may be due to the formation of different amounts of nonfluorescent oxidation products, especially the disulfide derivative. This view is supported by the observation that thiamine and its phosphate esters differ in their stability to alkalinity.