Abstract
Two types of sulfotransferases, namely recombinant rat liver aryl sulfotransferase AstIV and bacterial aryl sulfotransferase from Desulfitobacterium hafniense, were used for the sulfation of quercetin, its glycosylated derivatives (isoquercitrin and rutin), and dihydroquercetin ((+)-taxifolin). The rat liver enzyme was able to sulfate only quercetin and taxifolin, whereas the quercetin glycosides remained intact.
The D.hafniense enzyme sulfated isoquercitrin and rutin selectively at the C-4 position of the catechol moiety with very good yields. Taxifolin was sulfated at the C-4 position and a minor amount of the C-3 isomer was formed.
Sulfation of quercetin proceeded preferentially at the C-3 position, but a lower proportion of the C-4 isomer was formed as well. A detailed analysis of the kinetics of this reaction is provided and a full structural analysis of all products is presented.