คำศัพท์ทางการแพทย์Antioxidant Activity by ABTS Assay. The antioxidant the activity of the plant samples was determined by the ABTS cation radical method described by Re et al. A volume of 2.97 ml. of the cation radical solution was combined with 0.03 mL of each plant extract. The absorbance was measured at 734 nm after 20 min of incubation at room temperature. A control was prepared containing the cation radical solution of with no plant extracts. Aqueous 1% Tween 20 was used as the blank. Antioxidant activity, expressed as % of inhibition, was calculated using the formula mentioned in the DPPH assay