New nor-ursane type triterpenoids from Gelsemium elegans

Five new nor-ursane type triterpenoids, gelse-norursane A-E, together with twenty known compounds, were isolated from the whole plant of Gelsemium elegans. The structures of new compounds were established as (2R,3R,7R,17S,19R)-2,3,7,19-tetrahydroxy-6-oxo-24-norurs-4(23),12-dien-28-oic acid (1), (2R,3R,7R,17S)-2,3,7-trihydroxy-6-oxo-24-norurs-4(23), 12-dien-28-oic acid (2), (2R,3R,7R,17S)-2,3,4-trihydroxy-23-norurs-20(30),12-dien-28-oic acid (3), (2R,3R,30R)-2,3-dihydroxy-24-norurs-4(23),12-dien-30-oic acid (4), and (2R,3R,30R)-2, 3-dihydroxy-24-norurs-4,12-dien-30-oic acid (5), using spectroscopic analysis, including HRESIMS, 1D and 2D NMR. The absolute configurations of 1 and 4 were established through comparison of experimental and calculated ECD spectra. The gelse-norursane A-E are isolated as the 24-nor-ursane type triterpenoids from the family Loganiaceae for the first time. The cytotoxicities of the selected compounds against a panel of four human cancer HL60, Hela, Hep-G2, and Smmc 7221 cell lines were evaluated using the MTT assay in vitro.