The relative antioxidant activity and steric structure of green tea catechins - A kinetic approach

There are eight most abundant green tea catechins (GTCs) existing in four pairs of eipimers, and carbon-3 configuration represents the only steric difference within each pair. This study aimed to use a new kinetic approach to elucidate the effect of stereochemical changes on the antioxidant activity. A mixture of eight GTCs was treated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) prepared in a series of concentrations, their relative reaction rates towards scavenging DPPH were revealed by the recently introduced parameter, i.e. D_m. The 3-R configuration in (-)-epicatechin, (-)-epigallocatechin and (-)-epigallocatechin gallate gave lower D_m values demonstrating faster kinetics as opposed to their 3-S counterparts, with the only exception of the pair of (-)-catechin gallate and (-)-epicatechin gallate in which 3-S configuration was faster. These results suggested that the kinetic approach adopted in this study could reflect the different antioxidant activity of GTCs attributed by minor steric changes.