Four new triterpene saponins from Bupleurum rigidum L.

Four previously undescribed triterpene saponins (1-4) were isolated from the EtOH/H2O extract of the aerial parts of Bupleurum rigidum, together with a known structural analogue. Their structures were elucidated by analysis of 1D-(H-1, C-13) and 2D-NMR (H-1-H-1 COSY, TOCSY, ROESY, HSQC, HMBC) spectroscopic data and mass spectrometry (ESI- and HR-ESI-MS) and by comparison with those of related metabolites. An unusual structure was characterized as 3-O-beta-D-glucopyranosyl (1 -> 2)-[beta- D-glucopyranosyl (1 -> 3)]-beta-D fucopyranosyl-21-O-beta-D-glucoyranosy1-3 beta,16 beta,21 beta,23-tetrahydroxy-13,28-epoxyolean-11-ene (1). The three other compounds shared the same sugar sequence as 1 and differed by the structure of the aglycons, 3 beta,16 alpha,23,28,29-pentahydroxyoleana-11,13(28)-diene for 2, and 3 beta,16 alpha,23-trihydroxy-13,28-epoxyolean-11-ene for 3, and 4.