2.4.3. Percentage of reducing power
The determination of the reducing power percentage was made according to the method of Oyaizu (1986).
To 0.125 mL of the sample at a concentration of 1 mg/mL, 1.25 mL of phosphate buffer (200 mM, pH 6.6) and 1.25 mL of potassium ferricyanide (1%) were added.
The mixture was incubated at 50 C for 20 min. Then,1.25 mL of 10% trichloracetic acid was added to the mixture, which was centrifuged at 650 g for 10min.
An aliquot of 2.5mL was taken, 2.5 mL of distilled water and 0.5 mL of ferric chloride were added,and the absorbance measured at 700 nm with a UVeVIS spectrophotometer (Cary 100, Varian, Palo Alto, CA, USA). The results were
reported as the percentage of reducing power.
Absorbance of ascorbic acid at a concentration of 1 mg/mL was considered 100%
for reference.