Correlation between reduction potentials and inhibitory effects on Epstein–Barr virus activation by emodin derivatives

As a continuation of studies using natural and synthetic products as cancer chemopreventive agents, we examined the reduction–oxidation potentials of hydroxylated emodin derivatives prepared from emodin in phosphate buffer at pH 7.2 using cyclic voltammetry. A significant correlation was found between the reduction potentials and number of the hydroxyl groups and the inhibitory effects of the hydroxylated emodin derivatives on Epstein–Barr virus early antigen activation. The electronic properties, i.e. LUMO energy and atomic charges of carbon at the 9-position (C9) and oxygen at the 11-position (O11), may also be useful for estimating the inhibitory effect on EBV-EA activation.