Inhibitors of cyclic AMP phosphodiesterase in Panax ginseng C.A. Meyer and Panax japonicus C.A. Meyer.

Ginsenosides and chikusetsusaponins present in the roots of Panax ginseng C. A. MEYER and rhizomes of Panax japonicus C. A. MEYER were identified as inhibitors of cyclic AMP phosphodiesterase. The structure-activity relationships of 30 saponins, 2 prosapogenins and 3 sapogenins were studied. Saponins which have a 20 (S)-protopanaxadiol or oleanolic acid moiety as the sapogenin were generally more inhibitory towards cyclic AMP phosphodiesterase than saponins with a 20 (S)-protopanaxatriol moiety as the sapogenin. The effects of various ginsenosides on corticosterone secretion and cyclic AMP phosphodiesterase activity appeared to be parallel.