The ABTS radical cation (ABTS·+) scavenging activity of the sample was analyzed by using the method reported by Xiao
et al. (2014). ABTS·+ was generated by the reaction of a 7 mM aqueous solution of ABTS with 2.45 mM aqueous solution of K2S2O8 which was conducted in the dark at room temperature for 16 h before use. The ABTS·+ solution was diluted with ethanol to an absorbance of 0.70 (±0.02) at 734 nm and equilibrated at 30 °C. About 1 ml of different concentration extracts was mixed with 4 ml of ethanolic solution of ABTS·+, and the absorbance was read at 734 nm using a spectrophotometer after 6 min. The capability to scavenge the ABTS·+ was calculated using the following equation: