2,2-diphenyl-1-picrylhydrazyl radical scavenging assay

The modified method of Carmona-Jiménez et al.[13] using microtiter plate was used for the determination of DPPH-free radical scavenging potential. Briefly, 100 μl of methanol was added into all the wells except second (B) and third (C) rows. Then, 100 ml of different concentrations of the plant extracts (0.05 mg/ml) or standards prepared in MeOH was then added in triplicates from the third row (C) to the seventh row. Different concentrations of the plant extracts and standards from 0.05 to 0.01 mg/ml were prepared. A solution of 0.135 mM DPPH radical in methanol was prepared. One hundred microliters of this solution was then added into all the wells. The reaction mixture was then vortexed and left in the dark for 30 min at room temperature. The absorbance of the mixture was measured using a spectrophotometer at 517 nm. The actual decrease in absorbance was measured against that of the control. The scavenging ability of the plant extract was then calculated using the following equation:

DPPH scavenging activity (%) = ([{A_control-A_sample}]/A_control) ×100 Where A_control is the absorbance of DPPH + methanol and A_sample is the absorbance of DPPH + sample (or standard).