Ascorbate-quinone interactions: electrochemical, free radical, and cytotoxic properties.

Abstract
Standard midpoint potentials were determined for p-benzoquinone, methoxy-p-benzoquinone and 2,3-, 2,5- and 2,6-dimethoxy-p-benzoquinones in aqueous solution. ESR studies were made of the ascorbate and semiquinone radicals produced when these quinones interact with sodium ascorbate. Direct correlations are found between the electrochemical potentials, generated semiquinone lifetimes and cytotoxic action in Ehrlich ascites [mouse tumor cells]-bearing mice. [The cytotoxic action of quinone anticancer drugs may be mediated through their semiquinone free radical metabolites resulting from 1-electron redox reactions.].