The reducing power of extracts was determined by the method of Yuan et al. (2006) with some modifications.
2.0 mL test samples were mixed with 2.0 mL of phosphate buffer (0.2 mM, pH6.6) and 2.0 mL of 1% potassium ferricyanide (w/v).
The mixtures were incubated for 20 min at 50◦C. After incubation, 2.0 mL of 10% trichloroacetic acid were added to the mixtures, followed by centrifugation at 3000 rpm for 10 min.
The upper layer (2 mL) was mixed with 2 mL of distilled water and 0.4 mL of 0.1% ferric chloride.The reaction mixture was shaken well and incubated for 10 min,and the absorbance of the resultant solution was measured at700 nm.
Increased absorbance of the reaction mixture indicated increased reducing power of the samples.