2.8. Reducing power
Reducing power activities of ethanol and water extracts were
determined according to the method of Hu et al. (2009) with a little
modification; 1 ml of each sample or standard reagent (BHT as positive
control) at various concentrations (0.125–2.00 mg/ml) was
mixed with 2.5 ml of 0.2 M sodium phosphate buffer (pH 6.6)
and 2.5 ml of potassium ferricyanide (10 mg/ml) solution. Then
the mixture was incubated at 50 C in a water bath for 30 min
and mixed with 2.5 ml of TCA (100 mg/ml) and centrifuged at
3000 rpm for 10 min. 2.5 ml of the upper solution was transferred
and mixed with 2.5 ml of DW, followed by addition of 1 ml of FeCl3
solution (1 mg/ml). The absorbance was measured at 700 nm
wavelength. The effective concentration of each sample at 0.5
absorbance (EC50) was also evaluated.