2.2.6. ABTS Assay

17.2 mg ABTS was mixed with 3.3 mg K₂S₂O₈ and 5 mL of water as an oxidation starter; ABTS was oxidized to the corresponding radical cations (ABTS^•+) for 24 h and then kept in the freezer (at −20 °C). Then, 60 mL of distilled water was added to 1 mL of ABTS^•+ solution to test 70% CS ethanol extract’s radical scavenging activity. 2.5 mL ABTS solution was mixed with 0.5 mL CS extract solutions (each maturity stage of the CS sample was extracted for 60 and 90 min). Vitamin C was used as a comparison at the same concentration as that of CS extract samples; water was used as a reference. Absorbance was measured at 734 nm, and the inhibition level of ABTS^•+ was calculated by the following equation:

where A_i is the 734 nm absorbance of the control group at the initial time (0 min) and A_e is the 734 nm absorbance of the scavenger sample at the ending time [48].