Constituents of the root bark of Severinia buxifolia collected in Hainan.

Two new tetranortriterpenoids, 7-isovaleroylcycloseverinolide (1) and 7-isovaleroylcycloepiatalantin (2), together with 28 known compounds, were isolated and characterized from the root bark of Severinia buxifolia collected in Hainan. The structures of 1 and 2 were elucidated on the basis of spectral evidence including 2D NMR and X-ray techniques. The cytotoxicity of several acridone alkaloid isolates (3-8) was evaluated against a small tumor cell panel.