AGAPANTHUSSAPONINS A-D, NEW POTENT CAMP-PHOSPHODIESTERASE INHIBITORS FROM THE UNDERGROUND PARTS OF AGAPANTHUS-INAPERTUS

The saponin fraction prepared from the methanolic extract of the under ground parts of Agapanthus inapertus was found to exhibit inhibitory a ctivity on cAMP phosphodiesterase (55.2%) at a concentration of 100 mu g/ml. From this fraction, four new steroidal saponins, designated as a gapanthussaponin A (1), B (2), C (3) and D (4), were isolated as the a ctive principles, along with an inactive new furostanol saponin (5). T he structures of 1-5 were determined by spectroscopic data and hydroly sis. 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 papa verine (IC50 3.0 x 10(-5)M).