Electrochemical properties of some biologically active quinone derivatives: Furanquinones, pyridoquinones, and diplamine, a cytotoxic pyridoacridine alkaloid

The electrochemical propel-ties of 17 furanquinones, 5 pyridoquinones, and the iminoquinone diplamine in aprotic solvent systems were investigated. For the furanquinone and pyridoquinone derivatives, the quinone/semiquinone and semiquinone/dianion redox couples were observed as two successive one-electron transfer steps during cyclic voltammetry. For the pyridoquinones, two additional voltammetric waves attributed to nitro group reduction were observed at more negative potentials. The influence of molecular structure on quinone reduction potential is addressed. Reduction of diplamine was analogous to reduction of the quinones, occurring in two successive one-electron processes. In the presence of a proton donor, pyridoquinone reduction occurred via an ECEC mechanism. For the furanquinones, a general relationship is observed between reduction potential and reported inhibitory activity against various cancer cell lines.