Correlation between cytotoxic activities and reduction potentials of heterocyclic quinones.

To search for possible anti-tumor agents or anti-tumor promoters among natural or synthetic products, we used cyclic voltammetry to determine the reduction-oxidation potentials of heterocyclic quinones in phosphate buffer at pH 7.2. We determined the growth inhibitory- and cytotoxic activities of 12 heterocyclic quinone anti-tumor agent candidates against a panel of 39 human cancer cell lines (JFCR39). The average concentrations of the heterocyclic quinones required for 50% growth inhibition (GI(50)) against JFCR39 ranged from 0.045 to 13.2 µM, and the 50% lethal concentration (LC(50)) against JFCR39 ranged from 0.398 to 77.7 µM. The average values of GI(50) or LC(50) of the heterocyclic quinones correlated significantly with their reduction potentials. These results suggested that reduction-oxidation potentials could be a useful method for the discovery of novel antitumor agents.