Anti-oxidant capacity of dietary polyphenols determined by ABTS assay: A kinetic expression of the results

Abstract

The 2, 2′-Azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS)/Trolox equivalent anti oxidant capacity (TEAC) assay, which measures the ability of compounds to scavenge the ABTS radical cation (ABTS •+) in relation to Trolox (TEAC) is one of the most widely used methods to determine anti oxidant capacity. Usually, the measurements are based on a fixed end-point (4-6 min), which may not take into account the different kinetic behaviour of anti-oxidants. The aim of this work was to propose a kinetic procedure for ABTS•+ assay, by using the kinetic parameters ED50, tEC50 and AE [antiradical efficiency = 1/(ED50 × tEC50)], previously applied to the 2, 2-Diphenyl-1-picrylhydrazyl (DPPH•) assay. It was found that some polyphenols standards - ferulic acid, resveratrol and others-have not yet completed their reaction at the fixed end-point. The consideration of kinetic parameters in this method may provide a more thorough understanding of the behaviour of the anti-oxidants. A comparison of the activity of anti-oxidants measured by the scavenging of ABTS•+ with that of DPPH • was also carried out. © 2007 Institute of Food Science and Technology Trust Fund.