Tri- and Bicyclic Taxoids from the Taiwanese Yew Taxus sumatrana

Five new taxoids, including a new 2( 3 →20)-abeo-taxane with a 6/10/6-membered ring system and four 3,8-seco-taxanes having a 6/12-membered ring system, were isolated from an acetone extract of the leaves and twigs of the Taiwanese yew (Taxus sumatrana, Taxaceae) . The structures were established as 2α,7β,10α-triacetoxy-5α-hydroxy-2( 3 → 20)-abeo-taxa-4(20) ,11-dien-9,13-dione (1), (3E,8E)-2α,9,10β, 13α,20-pentaacetoxy-7β-hydroxy-3,8-secotaxa-3,8,11-trien-5-one (2), (3E,8E)-2α,9,10β,13α,20-penta- acetoxy-5α,7β-dihydroxy-3,8-secotaxa-3,8,11-triene ( 3), (3E,8E)-9,10β,13α-triacetoxy-2α,7β,20-trihy- droxy-5α-[(2E)-cinnamoyloxy]-3,8-secotaxa-3,8,11-triene (4), and ( 3E,8E)-2α,5α,7β,9,10b,13α-hexa- acetoxy-20-hydroxy-3,8-secotaxa-3,8,11-triene (5) , respectively, on the basis 1D- and 2D-NMR spectral analyses. The in vitro cytotoxic activity of compounds 1 – 5 against four human tumor cell lines, including HeLa (cervical epitheloid) , WiDr (colon), Daoy (medulloblastoma) , and Hep2 (liver carcinoma) tumor cells was evaluated. Whereas compounds 1 – 3 were inactive, the novel taxanes 4 and 5 showed significant cytotoxicity.