Agapanthussaponins A-D, New Potent cAMP Phosphodiesterase Inhibitors from the Underground Parts of Agapanthus inapertus.

Abstract

The saponin fraction prepared from the methanolic extract of the underground parts of Agapanthus inapertus was found to exhibit inhibitory activity on cAMP phosphodiesterase (55.2%) at a concentration of 100 micrograms/ml. From this fraction, four new steroidal saponins, designated as agapanthussaponin A (1), B (2), C (3) and D (4), were isolated as the active principles, along with an inactive new furostanol saponin (5). The structures of 1-5 were determined by spectroscopic data and hydrolysis. The IC50 of 1-4 on cAMP phosphodiesterase were 0.7, 1.2, 1.1 and 2.0 (x 10(-5) M), respectively, which are more potent than that of papaverine (IC50 3.0 x 10(-5) M).