Radical scavenging activity was determined by the method of Brand-Williams,Cuveleir, and Berset (1995), using DPPH as the free radical. The extraction of antioxidants was conducted as reported above. Five different concentrations of the extract were tested. These solutions(0.1 ml) were added to 3.9 ml of a 6 105 M methanol DPPH solution. The decrease in absorbance at 515 nm was determined at 25 C at zero time and every minute for the next 30 min until the registered curve reached a plateau. The exact initial DPPH
concentration (CDPPH) in the reaction was calculated by linear regression from a calibration curve with the Eq. (1):
Abs515 nm ¼ 12509 ðCDPPHÞ 2:58 103