ABTS Radical Scavenging Assay

For ABTS assay, the procedure followed the method of Arnao et al.[18 ] with some modifications. The stock solutions included 7 mM ABTS solution and 2.4 mM potassium persulfate solution. The working solution was then prepared by mixing the two stock solutions in equal quantities and allowing them to react for 14 h at room temperature in the dark. The solution was then diluted by mixing 1 ml ABTS solution with 60 ml methanol to obtain an absorbance of 0.706 ± 0.01 units at 734 nm using a spectrophotometer. Fresh ABTS solution was prepared for each assay. Plant extracts (1 ml) were allowed to react with 1 ml of the ABTS solution and the absorbance was taken at 734 nm after 7 min using a spectrophotometer. The ABTS scavenging capacity of the extract was compared with that of BHT and ascorbic acid and percentage inhibition calculated as ABTS radical scavenging activity (%)=Abscontrol-AbssampleAbscontrol where Abs_control is the absorbance of ABTS radical in methanol; Abs_sample is the absorbance of ABTS radical solution mixed with sample extract/standard. All determinations were performed in triplicate (n = 3).