Determination of DPPH Radical Scavenging Activity

Method of Truong et al. (2019) was followed for the determination of the antioxidant activity by DPPH. The extract was serially diluted to attain concentrations of 25, 50, 100 and 150 μg/ml. One ml of each dilution was mixed with 1 ml of DPPH solution (0.004% in ethanol) and incubated at 37°C for 30 min. The absorbance of the mixture was then measured spectrophotometrically at 517 nm. Absolute ethanol was used as a negative control. DPPH scavenging activity was calculated as follows: DPPH scavenging activity (%) = [(A⁰–A)/A⁰] × 100. Where, A is the absorbance of extract and A⁰ is the absorbance of the negative control (0.004% DPPH solution). Ascorbic acid was used as a positive control. The concentration required for a 50% inhibition of DPPH (IC₅₀) was then calculated by plotting the percentage of residual DPPH against the sample concentration.