Bioactive quassinoids from the seeds of Brucea javanica.

Six new quassinoids (1-6) and eight known compounds of this type (7-14) were isolated from the seeds of Brucea javanica. Their structures were elucidated by analysis of their spectroscopic data and from chemical evidence. Compounds 1-5 were found to be unusual quassinoids with a 2,3-seco A ring. The configurations at C-4 in 4 and 5 were determined by a difference circular dichroism method. In in vitro bioassays, 8 and 10 showed inhibitory activities for nitric oxide production in LPS-activated macrophages, with IC(50) values of 1.9 and 5.0 µM, respectively, while compounds 6, 8-11, 13, and 14 exhibited cytotoxicity against five human tumor cell lines (HCT-8, HepG2, BGC-823, A549, and SKVO3), having IC(50) values in the range 0.12-9.3 µM.