Antiproliferative Constituents from Umbelliferae Plants VI. New Ursane-Type Saikosaponin Analogs from the Fruits of Bupleurum rotundifolium

The MeOH extract of the fruits of Bupleurum rotundifolium showed inhibitory activity against human gastric adenocarcinoma (MK-1) cell growth (GI50: 6.25 μg/ml). From this extract, 10 new ursane-type triterpene glycosides viz. three 3-O-triosides (called rotundifoliosides A, I, and J) of 13β,28-epoxy-3β,16α-dihydroxyurs-11-ene, two (G and H) of 13β,28-epoxy-3β,16α,23-trihydroxyurs-11-ene, two (E and F) of 13β,28-epoxy-3β,16α,21β-trihydroxyurs-11-ene, two (B and C) of 3β,11α,16α,28-tetrahydroxyurs-12-ene, and one (D) of 3β,11α,28-trihydroxy-15α,16α-epoxyurs-12-ene were isolated in addition to 16 new oleanane-type triterpene glycosides (rotundiosides J—Y), echinocystic acid 3-O-sulfate and 3 known oleanane-type triterpene glycosides (rotundiosides A, F and G). The isolation, structures and antiproliferative activity of the new ursane-type triterpene glycosides against MK-1, human uterus carcinoma (HeLa), and murine melanoma (B16F10) cell lines are described with some comments on the structural requirements for their activity.