2.11.1. ABTS Radical Scavenging Assay

ABTS radicals were propagated by oxidation of ABTS (7.0 mM) with potassium persulfate (K₂S₂O₈, 4.95 mM) in the dark (12 h) at 25 °C. Then, ABTS was diluted with PBS (0.2 M, pH 7.4) to reach an absorbance value of 0.7 measured at 734 nm. The absorbance value of a mixture of a 20 μL sample and 200 μL of the working solution was measured at 734 nm by a microplate reader (Veloskan™ LUX, Thermo Fisher Scientific, Waltham, MA, USA) after 30 min of reaction. The scavenging activity was reported as ABTS radical inhibition (%) and calculated according to Equation (3).

where the absorbance of water instead of the sample was the control (Abs₀); the absorbance of the sample with ABTS is Abs₁ and the absorbance of the water instead of ABTS is Abs₂. Trolox standard solution was prepared and assayed under the same conditions. Results are expressed in terms of TEAC, which represents the mmol/L Trolox equiv/g sample.