Free thiamin is unstable because of its quaternary nitrogen; in water, it is cleaved to
the thiol form. For this reason, the hydrochloride and mononitrate forms are used in
commerce. Thiamin hydrochloride (actually, thiamin chloride hydrochloride) is a
colorless crystal that is very soluble in water (1 g/ml, thus making it a very suitable
form for parenteral administration), soluble in methanol and glycerol, but practi cally insoluble in acetone, ether, chloroform, and benzene. The mononitrate form is
more stable than the hydrochloride form, but it is less soluble in water. It is used in
food/feed supplementation and in dry pharmaceutical preparations. Free thiamin is
easily oxidized to thiamin disulfide and other derivatives, including thiochrome, a
yellow biologically inactive product with strong blue fluorescence that can be used
for the quantitative determination of thiamin. Its metabolically active form is thia min diphosphate, also called thiamin pyrophosphate.
ChEBI: Thiamine(1+) is a primary alcohol that is 1,3-thiazol-3-ium substituted by (4-amino-2-methylpyrimidin-5-yl)methyl, methyl and 2-hydroxyethyl groups at positions 3, 4 and 5, respectively. It has a role as a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite. It is a primary alcohol and a vitamin B1. It is a conjugate base of a thiamine(2+).
