Inhibition of adenosine deaminase activity of aortic endothelial cells by selected flavonoids.

Flavonols like quercetin, myricetin, and kaempferol inhibit the activity of the adenosine deaminase of endothelial cells (IC50 between 26 and 32 mumol/l), while flavones are inactive. These results support the suggestion that many pharmacological actions of flavonoids are mediated by an amplification of the effect of endogenous adenosine via adenosine receptors because adenosine deaminase is responsible for the adenosine inactivation.