Computation of the redox and protonation properties of quinones: Towards the prediction of redox cycling natural products

Quinone metabolites perform a variety of key functions in plants, including pathogen protection, oxidative phosphorylation, and redox signaling. Many of these structurally diverse compounds have been shown to exhibit potent antimicrobial, anticancer, and anti-inflammatory properties, although the exact mechanisms of action are far from understood. Redox cycling has been proposed as a possible mechanism of action for many quinone species. Experimental determination of the essential thermodynamic data (i.e. electrochemical and pK(a) values) required to predict the propensity towards redox cycling is often difficult or impossible to obtain due to experimental limitations. We demonstrate a practical computational approach to obtain reasonable estimates of these parameters. (c) 2006 Published by Elsevier Ltd.