2.6.2. Reducing power property
The reducing power of extracts was determined according to the method suggested by Yen and Chen [22]. Different concentrations of each extract (25–500 μg/mL) were mixed with phosphate buffer (2.5 mL, 0.2M, pH 6.6) and potassium ferric cyanide [K3Fe(CN)6] (2.5 mL, 1%). The mixture was incubated at 50°C for 20 minutes. A portion (2.5 mL) of trichloroacetic acid (10%) was added to the mixture to stop the reaction, and the mixture was centrifuged at 3000 rpm for 10 minutes. The upper layer of solution (2.5 mL) was mixed with distilled water (2.5 mL) and ferric chloride (0.5 mL, 0.1%), and the absorbance was measured at 700 nm. A similar procedure was repeated with respective solvent instead of the extract, which served as the control. Ascorbic acid was used as the standard. All tests were performed in triplicate. Increased absorbance of the reaction mixture indicates the increased reducing power [23].