100 mL of the diluted sample extract
(prepared at 5 different concentrations which were providing 10–
90% inhibition for DPPH radical) was added into 4 mL of freshly
prepared DPPH (2,2-diphenyl-1-picryhydrazyl radical) solutions
(6 105M in MeOH). The mixtures were shaken and kept in the
dark at room temperature for 30 min. Absorbance values of the
final solutions were recorded at 515 nm using a spectrophotometer
(Analytic Jena UV–vis L 40, Germany) with respect to control
solution (80% MeOH instead extract in DPPH solution). The
antioxidant activity of the samples was expressed as percentage
inhibition of the DPPH radical which was calculated by using the
following Eq. (1):