3.5.2. ABTS Radical Scavenging Assay

The ABTS assay was measured according to [42] with some modifications. Briefly, 10 mM phosphate-buffered saline (PBS) solution solved 12.5 mM of ABTS and 2,2-azobis (2-amidinopropane) dihydrochloride (ABAP), which pH was at 7.2. The mixture was completely blended in the incubator for 40 min at 68 °C and monitored under spectrophotometer, which the absorbance was 0.65 ± 0.020 at 734 nm. The scavenging activity was measured at 734 nm after 20 µL of sample and 980 µL of ABTS⁺ solution were mixed in a tube and then incubated for 10 min at 37 °C. 20 µL deionized water in 980 µL ABTS⁺ solution was considered as control consist.

By measuring the DPPH and ABTS⁺ scavenging activities of 20–100 mg vitamin C/L, the standard curves of the two assays were collected. The DPPH and ABTS⁺ scavenging activities were expressed as mg vitamin C equivalent (VCE)/100 g dried weight. All extracts were tested after being diluted 100 times to ensure the accuracy of the test results. Besides, each sample was done in triplicate.