Anti‐oxidant capacity of dietary polyphenols determined by ABTS assay: a kinetic expression of the results

Summary 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 ED 50 , t EC50 and AE [antiradical efficiency = 1/(ED 50 × t EC50 )], 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.