3.2.2. Reducing power
The reducing power of the extract, which may serve as a reflection of its antioxidant activity, was determined using a
modified Fe3þ to Fe2þ reduction assay, whereby the yellow color of the test solution changes to various shades of green and blue, depending on the reducing power of the sample. The presence of antioxidants in the sample causes the reduction of Fe3þ/ferricyanide complex to the Fe2þ form, which is monitored by measuring the formation of Perl’s Prussian blue at 700 nm [24]. In Fig. 2, all extracts show some degrees of electron-donating capacity in a concentration-dependent manner. The 100% ethanol extract once again gave the highest reducing power and is significantly higher (p < 0.05) than that of the other extracts at all concentrations studied, followed by that of the 100% acetone extract, the 100% methanol extract, and the extracts obtained by different concentrations
of aqueous acetone, aqueous ethanol, and aqueous methanol. The reducing power of the 100% acetone extract at concentrations ranging from 60 mg/mL to 100 mg/mL is insignificantly higher than that of the 100% methanol extract and the extracts of aqueous ethanol, aqueous methanol, and aqueous acetone. However, at concentrations higher than 100 mg/mL, the reducing power of the 100% acetone extract is significantly higher (p < 0.05) than that of the extracts of 100% methanol, aqueous ethanol, aqueous acetone, and aqueous methanol. The lowest reducing power was found in the water extract. Its value is also significantly lower than that of the other extracts
at all concentrations studied.