2.4.1. Radical-Scavenging Activity

The radical-scavenging activity was measured via ABTS (Re et al., 1999) and DPPH (Brand-Williams et al., 1995) assays. ABTS⁺ was produced by reacting 7 mM ABTS stock solution with 2.45 mM K₂S₂O₈, allowing the mixture to stand in the dark at RT for 16 h before use. The solution was diluted until it reached a final absorbance of 0.70 at 734 nm. The absorbance at 734 nm was recorded for 5 min after the mixing of 10 µL of extract (or antioxidant standard) with 1 mL ABTS⁺ solution using a spectrophotometer with ethanol as blank. DPPH assay was carried out, adapting the protocol to a spectrophotometric reading using a microplate reader [13]. Briefly, 0.5 mL of 0.1 mM DPPH solution was diluted until it reached a final absorbance of 0.90 at 517 nm. Consequently, 190 µL of the diluted reaction mixture was added to 10 µL of properly diluted fruit extract. After 20 min, the absorbance was read at 517 nm with ethanol as blank. For both assays, the inhibition percentage was calculated using the following equation (Equation (2)):

where IP(%) is the percentage of color reduction of the reagent mixture; A_CTR is the absorbance of ABTS and DPPH solution at the respective wavelengths (734 nm for ABTS assay or 517 nm for DPPH assay) before the addition of the extract; while A_TEST is the absorbance of ABTS and DPPH solution after the addition of the extract read at the respective wavelengths (734 nm for ABTS assay or 517 nm for DPPH assay) at the end of incubation time. Trolox was used as a reference standard, and the antioxidant activity of each assay was expressed as mmol of Trolox equivalent (TE) per 100 g of FW. The experiments were repeated three times.