ABTS radical scavenging assay

The total antioxidant activity determined by radical cation (ABTS^• +) decolonization assay was performed according to the procedure described in the literature with slight modifications (Zhao et al., 2011; Olajire & Azeez, 2011). The radical cation reagent (ABTS^• +) solution was prepared by mixing similar quantities of 7 mM of ABTS^• + and 2.4 mM of potassium persulfate (K₂S₂O₈) solutions and allowing them to react in dark for 16 h and at room temperature. Before use; this solution was diluted with methanol to get an absorbance of 0.75 ± 0.02 at 734 nm. To measure the antioxidant power of the plants’ extracts, 3 ml of ABTS^• + reagent solution and 1 mL of each extract at various concentration levels (ranging from 0.005–0.500 mg/ml) were mixed and the absorbance was then measured at 734 nm on Wavelight II UV- visible spectrophotometer (Version 7120V1.8.0, USA). Blank sample was run in each assay and all measurements were done after at least 5 min. Ascorbic acid and α-tocopherol were used as positive controls. All measurements and IC₅₀ value determinations were conducted in triplicates.