2.9.5. ABTS Assay

ABTS radical scavenging activity was determined according to the method employed by [19] [20] with slight modifications. Previously prepared ABTS solution and potassium persulfate (K₂S₂O₈) were mixed in 1 : 1 ratio. The reaction mixture was left to stand at 37°C for 16 h under dark conditions. ABTS/K₂S₂O₈ solution was diluted with 70% methanol with a ratio of 1 : 40 (to obtain an absorbance at 0.8000-0.700). 0.04 mL of the sample extract was added to 4.0 mL of ABTS/K₂S₂O₈ solution. The solution was mixed well and kept in dark for 15 min. The absorbance of the samples was measured at 734 nm using a UV-Vis spectrophotometer. The results were expressed as Trolox equivalent (TE) in milligram per g of dried sample using a calibration curve of Trolox (y = −0.0012x + 0.756, R² = 0.9946).