Inhibition of Cyclic AMP Phosphodiesterase by Flavonoids

Abstract

Nobiletin and irigenin were identified as inhibitors of cyclic AMP phosphodiesterase, which were contained in peels of immature fruits of Citrus reticulata BLANCO (Japanese name "Seihi") and in rhizomes of Iris florentina L. The structure activity relationships of 33 flavonoids were studied and polymethoxy flavonoids were generally more inhibitory against cAMP phosphodiesterase than corresponding polyhydroxy flavonoids. Nobiletin, irigenin and pentamethyl quercetin showed inhibitory effect on barium sulphate transport in the small intestine of mice. Further pharmacological investigations have revealed that these flavonoids have cholinergic activity.