4.2. Superoxide Scavenging Activity

The high-throughput superoxide (O2−•) scavenging assay was carried as reported by Tao et al. [31]. Four different concentrations were used for each antioxidant compound in the study. We used p-coumaric acid (p-Coum) as reference compound. The scavenger sample solution (TA1, T1AM, p-Coum, (final concentration range 3–100 μM; 6.67 μL) and 193.33 μL of substrate solution (including 6.43 μL of 4 mM xanthine, 12.86 μL of 4 mM NBT, and 174.04 μL of 0.05 M PBS) were added to each well. Next, 20 μL of 0.04 U/mL XO solution was added to start the reaction. After gentle shaking for 10 s, the reaction mixture was incubated at 37 °C for 20 min. Finally, 20 μL of 0.6 M HCl was added to stop the reaction, followed by shaking for another 10 s. The absorbance at 560 nm was measured. The total volume for each reaction mixture in each well was 240 μL. A blank test without XO and a control test without antioxidants were also conducted. The superoxide scavenging activity was expressed as percentage (%) of superoxide quenching, which was calculated as (1 − B/A) × 100, where B and A are the activities of xanthine oxidase with and without the addition of sample solution, respectively.