3.7. DPPH Radical Scavenging Activity

The DPPH radical scavenging assay was measured as described with minor revisions [31]. The assay mixture in each well of the 96-well plates included 200 µM DPPH solution (dissolved in ethanol, 100 µL) and different concentrations of test compounds (100 µL). After 30 min at room temperature and in darkness, the absorbance of mixture was measured at 520 nm. DPPH radical scavenging activity was calculated with following formula,

DPPH scavenging activity (%) = (A_c − A_t)/A_c × 100, where A_t is the absorbance of the test sample and A_c is the absorbance of the control. Commercially-available BHT was used as positive control. All half maximal inhibitory concentration (IC₅₀) values of tested activities were determined by the liner regression of the percentage of remaining DPPH radical against the sample concentration.