Bioactivity-guided isolation of cytotoxic constituents of Brucea javanica collected in Vietnam.

Five new triterpenoids (1-5), together with two known quassinoids, bruceantin (6) and bruceine A (7), and a known flavonolignan, (-)-hydnocarpin (8), were isolated from the chloroform-soluble subfraction of a methanol extract of the combined twigs, leaves, and inflorescence of Brucea javanica collected in Vietnam. The structures of the new compounds 1-5 were established on the basis of spectroscopic methods. All isolates were evaluated for cytotoxicity against a small panel of human cancer cell lines. Quassinoids 6 and 7 were found to be highly active against these cell lines. (-)-Hydnocarpin (8) showed a potentiating effect when combined with both 6 and 7, during cytotoxicity testing using the MCF-7 human breast cancer cell line.