DPPH radical scavenging activity

The free radical scavenging activity of all the extracts was evaluated by DPPH according to the method previously reported by Blois²⁰ in 1958. Briefly, a 0.1 mM solution of DPPH in ethyl alcohol was prepared and 1 mL of this solution was added to 3 mL of the solution of all extracts in methanol at different concentrations (5, 10, 15, 20, and 25 µg/mL). The mixtures were shaken vigorously and allowed to stand at room temperature for 30 min. Then the absorbance was measured at 541 nm using a UV-Vis spectrophotometer. Ascorbic acid was used as the reference. Lower absorbance values of the reaction mixture indicate higher free radical scavenging activity. The capability of scavenging the DPPH radical was calculated using the following formula:

DPPH scavenging effect (% inhibition)={(A0-A1)/A0)×100},

where A0 is the absorbance of the control reaction and A1 is the absorbance in the presence of all of the extract samples and reference. All the tests were performed in triplicate and the results were averaged.