Determination of antioxidant activity by DPPH free radical scavenging assay

The 2, 2-diphenyl-1-picrylhydrazyl free radical-scavenging activity was determined by standard methods with slight modification^28,29. Various concentrations (100, 80, 60, 40, 20, 10, and 5 µg/mL) of the solvent fractions of V. cinerea were prepared in methanol. The DPPH solution was freshly prepared for the assay. Each extract solution (2 mL) was mixed with 1 mL of methanol solution containing DPPH radicals (0.2 mM). The reaction mixtures were prepared under dim light, shaken vigorously and maintained for 30 min in the dark after which the absorbance was measured at 517 nm using a UV-VIS Spectrophotometer. The absorbance of the control was obtained by replacing the sample with methanol. Quercetin and gallic acid were used as standards. The scavenging activity was calculated using the formula:

Scavenging activity (%) = (A517 of control − A517 of sample) / A517 of control ×100.

IC₅₀ values (the concentration of sample, which is required to scavenge 50% of DPPH radicals) were determined.