A "zero sample concentration approach": standardization of methods for the estimation of total antioxidant activity by the use of extrapolation to zero sample concentration. A novel standard. 1. ABTS cation radical scavenging.

The study presents the general method of standardization of estimations of total antioxidant activity (TAA) by extrapolating parameters to zero sample concentration based on a pseudo-first-order kinetics model. To test its suitability, the method was applied to the ABTS cation radical scavenging assay, as the first choice. Two alternative methods of extrapolation were presented, via linear regression and numerical fitting to the dose-response profile. An extrapolation method gives the highest value of estimates, independent of sample concentration, and creates a new standard approach to the methods of TAA estimation. It is proposed to designate the modified index as "standard equivalent antioxidant capacity at zero" (SEAC0) or TEAC0 (for Trolox as standard). The examples of estimates for some foods and rat plasma are presented and compared with the literature method. The applicability of the extrapolation approach to the other TAA measurement methods is under evaluation.