Bioreductive activation of quinones: redox properties and thiol reactivity.

Redox properties and thiol reactivity are central to the therapeutic and toxicological properties of quinones. The use of other physicochemical parameters to establish predictive relationships for redox properties of quinones is discussed, and attention drawn to situations where such relationships may be unreliable. The rates of reaction of semiquinone radicals with oxygen, including those of chemotherapeutic agents such as mitomycin and the anthracyclines, can be predicted with reasonable confidence from the redox properties. The reactions of quinones with thiols such as glutathione produces reduced quinones and radicals, but the reactions are complex and all the features are not well understood.