3.6.2. ABTS Radical Scavenging Assay

ABTS radical scavenging activity was detected as reported in previous research with some modifications [28]. Potassium persulfate (2.6 mM) was added into ABTS (7.4 mM) to obtain the ABTS stock solution. Then, the solution was incubated at room temperature in dark for 12 h. Deionized water was used to dilute the solution to prepare the ABTS working solution (0.70 ± 0.02 absorbance at 734 nm). After that, 4 mL ABTS working solution with 1 mL sample were mixed for 6 min in the dark. Subsequently, the absorbance of mixture was recorded at a wavelength of 734 nm using a TU-1901 double beam UV-Visible spectrophotometer (Persee, Beijing, China). Ascorbic acid was selected as a positive control. The formula of the ABTS scavenging rate was listed below:

$$\text{ABTS scavernging rate (\%)} = (1 - \text{A}\_{\text{i}}/\text{A}\_{\text{0}}) \times 100$$

In the equation, A0 and Ai separately indicated the absorbance values of the blank control and the sample.
