Three ABTS(center dot+) radical cation-based approaches for the evaluation of antioxidant activity: fast- and slow-reacting antioxidant behavior

摘要

This work focuses on the behavior and comparative assessment of the antioxidant activity of several well-known antioxidants using three different approaches with the same ABTS(aEuro cent+)/potassium persulfate radical-generating system: a decolorization assay, kinetic assay, and visual-spectrophotometric titration assay. The decolorization assay is the most common approach but gives little information on antioxidant behavior. The kinetic assay can be used for an in-depth study of the specific features of a particular antioxidant and facilitates identification of the mechanism of action. The visual-spectrophotometric titration assay is complementary to the above assays and subdivided into two stages to demonstrate the contribution of the "fast" and "slow" scavenging properties to the total antioxidant activity. The trolox equivalent antioxidant capacity (TEAC) value ranges for several flavonoids and the endogenous antioxidants derived from these assays vary from 0.7 to 5.1, 0.5-2.8, and 0.4-3.7, respectively, while the sequence of the weakest antioxidant to the strongest is similar. The analysis of the kinetic curves for some flavonoids showed that their interaction with ABTS(aEuro cent+) has an atypical character. Based on the results of the kinetic and visual-spectrophotometric titration assays, fast-reacting (trolox, alpha-tocopherol), slow-reacting (naringenin, apigenin) and moderate-reacting antioxidant (dihydroquercetin, quercetin, rutin, morin, and glutathione) compounds were distinguished.