DPPH radical-scavenging activity

The antioxidant activity of the essential oils was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) as described previously by Brand-Williams et al., 1995 [29]. This assay assess the radical scavenging activity of the DPPH by the tested sample. Five concentrations (10, 50, 100, 500 and 1000 μg/mL) of each essential oil were prepared. Then 500 μL of the essential oil was added to 125 μL DPPH methanol solution (1 mM) and 375 μL methanol and incubated for 30 min at room temperature in the dark. At the, the anti- DPPH radical-scavenging activity was measured by recording the absorbance at λ = 517 nm and calculated using the following formula: