Free radical-scavenging activity
Antioxidant activity was measured in term of the scavenging of the stable free radical, 1,1-diphenyl-2-picrylhydrzyl (DPPH) by the method proposed by Shimada et al (1992). A sample of each fraction (2.0 ml), in methanol, was added to 2.0 of a solution that contained DPPH. After 30 min, the absorbance was measured at a wavelength of 517 nm using UV-visible spectrophotometer. The DPPH radical-scavenging activity was calculated according to the following: % of DPPH scavenging activity = {1- (AbS/AbC)} x 100, where AbC was the absorbance of the control and AbS was the absorbance in the presence of the test compound. EC50 is the effective concentration of the extract in milligram/milliliter which inhibits the DPPH activity by 50%.