The scavenging effects of samples for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical were monitored according to the method of the previous report by Yen and Chen (1995). Briefly, 2.0 ml aliquot of test sample (in methanol) was added to 2.0 ml of 0.16 mM DPPH methanolic solution. The mixture was vortexed for 1 min and then left to stand at room temperature for 30 min in the dark, and its absorbance was read at 517 nm. The ability to scavenge the DPPH radical was calculated using the following equation:
Where, Acontrol is the absorbance of the control (DPPH solution without sample); Asample is the absorbance of the test sample (DPPH solution plus test sample) and Asample blank is the absorbance of the sample only (sample without DPPH solution). Synthetic antioxidants: BHT, gallic acid and ascorbic acid were used as positive controls.