2.8.2. Assay of ABTS+• Radical Scavenging Activity

The method reported by Awe et al. [29] was adopted for the assay of ABTS+• radical scavenging activity. First, ABTS was dissolved in phosphate buffered saline (PBS, 0.01 M, pH 7.4) to a 7 mM concentration. The ABTS solution was then mixed with an equal volume of K2S2O8 solution (2.45 mM) in the dark at room temperature to produce ABTS+•. After 16 h, the ABTS+• solution was adjusted to a suitable absorbance (0.70 <sup>±</sup> 0.02) using water at 734 nm. To 2.0 mL of the prepared ABTS+• solution, 0.5 mL of various concentrations of extract solution (25–150 μg/mL) was added. The reaction mixture was then incubated in the dark at room temperature. A total of 10 mins later, the absorbance of the mixture was immediately recorded at 734 nm. Trolox was used as a positive control in this experiment, and the percentage of ABTS+• radical scavenging was calculated using the Equation (4).
