2.7.3. Ferric Reducing Antioxidant Power (FRAP) Assay

The FRAP assay is another method for detecting antioxidant capacity. FRAP reagent was prepared using a previously described method [1,35]. In brief, 300 mM acetate buffer (pH 3.6), 10 mM TPTZ (2,4,6-tripyridyl-s-triazine) solution in 40 mM hydrochloric acid, and 20 mM iron (III) chloride were mixed in a 10:1:1 ratio. FRAP reagent (150 μL) was mixed with 20 μL of the sample, 20 μL of ascorbic acid (positive control), and 20 μL of DW (blank). The absorbance of each was measured at 593 nm. The FRAP value was calculated using the following equation:

FRAP value = [(A₁ − A₀)/(A_c − A₀)] × 2, where A_c is the absorbance of the positive control, A₁ is the absorbance of the sample, and A₀ is the absorbance of the blank.