Antiplatelet aggregation triterpene saponins from the barks of Ilex rotunda

Abstract

Four new triterpene saponins, rotundinosides A–D (1–4) and seven known triterpene saponins (5–11) were isolated from a methanol extract of the barks of Ilex rotunda Thunb. The new saponins were characterized as 3-O-β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl siaresinolic acid 28-O-β-d-glucopyranoside (1), 3-O-[β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopranosy1ester (2), 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopyranosy1 ester (3), and 3-O-α-l-rhamanopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl ilexgenin B 28-O-β-d-glucopyranosy1 ester (4), respectively. Their structures were established by extensive spectroscopic analysis, including HSQC, HMBC, 1H–1H COSY, NOESY and acid hydrolysis, and also by the comparison of their spectroscopic data with those of related compounds. The known compounds 5–11 were all obtained from this species for the first time. The biological activity of compounds 1–11 against ADP induced platelet aggregation in rabbit plasma was determined. Among the tested compounds 1, 3, 5 and 10 exhibited strong inhibition of platelet aggregation in vitro, with IC50 values of 11.4±2.2, 10.4±1.3, 13.2±2.4, and 15.1±3.4μM, respectively.