Pentasubstituted quercetin analogues as selective inhibitors of particulate 3':5'-cyclic-AMP phosphodiesterase from rat brain.

Some penta-O-substituted analogues of quercetin were synthesized and tested for the inhibition of cytosolic and particulate rat brain cyclic AMP and cyclic GMP phosphodiesterase activities. Ten of these compounds are potent and highly selective inhibitors of cAMP hydrolysis with respect to cGMP hydrolysis. They inhibit more potently the particulate enzyme than the cytosolic preparation. The highest selectivity was observed with penta-O-ethylquercetin and analogue 6d, which proved to be more selective and more potent inhibitors than the reference compound Ro 20-1724. Some structure-activity relationships are discussed.