Spirostanol saponins from Ypsilandra parviflora induce platelet aggregation

Phytochemical investigation on the whole plants of Ypsilandra parviflora led to the isolation of seven new spirostanol saponins, named ypsiparosides A-G, together with 14 known saponins. Their structures were unambiguously established based on extensive spectroscopic evidence and chemical methods. The induced rabbit platelet aggregation activities of the isolates were tested. Compounds 4, 15, and 17 showed maximal platelet aggregation rates ranging from 43 to 55% at a concentration of 300μg/mL. Further experiments exhibited that compounds 4, 15, and 17 possessed EC₅₀ values of 642.9, 95.3, and 300.8μg/mL, respectively.