2.7. DPPH Radical Scavenging Activity Assay

The DPPH radical scavenging activity screening of the isolates was based on a method reported previously [23]. First, 190 µL of the DPPH solution (100 µM) and 10 µL of the tested samples with various concentrations were placed in a 96-well plate and then incubated for 30 min in darkness at room temperature. Vitamin C was used as the positive control and methanol as the blank control. After the incubation, the absorbance of the reaction mixture was measured with a microplate reader at 517 nm, and the IC₅₀ value was calculated by GraphPad Prism software. Following the same procedures above, all of the tests were repeated three times independently.