Oncocalyxones A and C, 1,4-anthracenediones from auxemma oncocalyx: Comparison with anticancer 1,9-anthracenediones

Oncocalyxones A and C are 1,4-anthracenediones isolated fi om Auxemma oncoc alyx (Boraginaceae) that have been shown to be cytotoxic to tumor cells in vitro. The present study compared the cytotoxicity of these compounds with that of two conventional anticancer agents doxorubicin and mitoxantrone, bo th 1,9-anthmcenediones, in a panel of human. tumor cell lines. The effect o n cell growth was examined using an MTT microtiter assay in two leukemia li nes, five solid tumor fines of different histological origin, and two multi drug-resistant sublines of a lung tumor line. The oncocalyxones showed much lower potency than the 1,9-anthracenediones, but were similarly more cytot oxic to leukemia cells compared to solid tumor lines. However; in the multi drug-resistant cells with 10 to 500 times decreased sensitivity to doxorubi cin, the cytotoxicity of oncacalyxones A and C was only modestly reduced by about twofold. 1,4-Anthracenediones may be a promising novel class of chem otherapeutic agents effective against multidrug resistant tumors.