Potentiating effect of obacunone from Dictamnus dasycarpus on cytotoxicityof microtuble inhibitors, vincristine, vinblastine and taxol

The limonoid triterpene, obacunone, was found to enhance the cytotoxicity o f vincristine against L1210 cells by approximately 10-fold. Further, it was found that the cytotoxicity of other microtubule inhibitors such as vinbla stine and taxol in drug-sensitive KB-3-1 cells as well as in multidrug-resi stant KB-V1 cells was enhanced greatly in the presence of obacunone. On the other hand, there was no remarkable potentiating effect of obacunone on th e cytotoxicity of other antineoplastic drugs such as adriamycin, cisplatin or 5-fluorouracil. From these results, it is implied that: the potentiating action of obacunone may be limited to microtubule inhibitors.