In vitro cytotoxicity of a series of quassinoids from Brucea javanica fruits against KB cells.

A microdilution technique was developed for the assessment of in vitro cytotoxicity against KB cells derived from a human epidermoid carcinoma of the nasopharynx. The test was used to determine the cytotoxicity of a series of quassinoids, isolated from Brucea javanica, and which have previously been shown to demonstrate activity against Plasmodium falciparum. The 50% effective dose (ED50) for 7 quassinoids tested against KB ranged from 0.008 microgram/ml for bruceantin, the most cytotoxic of the compounds tested to greater than 5 micrograms/ml for bruceolide, the least toxic tested. The activities of the quassinoids against KB did not parallel the known activities of the quassinoids against Plasmodium falciparum suggesting that the quassinoid mode of antimalarial action is not a simple cytotoxic effect and lends support to further investigation of the structure activity relationships within this group of compounds.