2.6. The Antioxidant Activity (DPPH, ABTS, and FRAP)

The antioxidant activities were evaluated in ten-fold diluted supernatants prepared for TPC analyses. The analyses were made in 4 replicates.

For the DPPH assay, ethanol (1.5 mL) and DPPH solution (0.5 mL) were added to the supernatants (0.5 mL), properly mixed and incubated in the dark at room temperature (10 min). The absorbance was measured at a wavelength of 517 nm [29,30,36].

For the ABTS assay, a diluted ABTS solution (3 mL) was added to the supernatants (30 μL) and left in the dark (6 min). The absorbance was measured at a wavelength of 734 nm [29,30,37,38].

For the FRAP assay, a FRAP reagent (3 mL) was added to the supernatant (1 mL), and the mixture was kept to react (10 min). The absorbance was measured at a wavelength of 593 nm [29,30,39].