2.5. Antioxidant capacity
The ferric-reducing antioxidant power (FRAP) assay was based on the method of Benzie and Strain (1996). The fresh FRAP reagent was prepared by mixing 25 mL 300 mM sodium acetate-acetic acid buffer (pH 3.6), 2.5 mL 20 mM FeCl3 and 2.5 mL 10 mM TPTZ (2,4,6tripyridyl-s-stiazine). For this analysis, 20 L aliquot of methanol extract, prepared as described in Section 2.4, was mixed with 980 L FRAP reagent. The mixture was kept at 20◦C for 4 min before absorbance was determined at 593 nm wavelength. Antioxidant capacity, expressed as micromol ferrous ion per g of fresh weight