2.6.1. Trolox Equivalent Antioxidant Capacity Assay (TEAC)

The TEAC assay measures the reduction of the radical cation ABTS⁺ by antioxidant compounds. The spectrophotometric method proposed by Barba et al. [28] was used. The ABTS+ radical cation stock solution was generated by chemical reaction with 7 mM ABTS and 140 mM K₂S₂O₈ overnight in darkness at room temperature. Next, it was diluted in ethanol until an absorbance of 0.700 ± 0.020 at 734 nm and 30 °C to obtain the ABTS+ working solution. The optimization of the adequate dilution of the samples to obtain a percentage of absorbance inhibition of approximately 50% was required. Trolox standard solutions were prepared in a range of 0 to 300 μM. The absorbance of 2 mL of ABTS⁺ working solution was considered the initial point of reaction (A₀). Then, 100 μL of diluted samples or Trolox standards were added immediately. The absorbance after 3 min of reaction was considered the final point (A_f). All readings were carried out in a thermostatized UV–vis spectrophotometer. The percentages of absorbance inhibition were calculated from the following equation: 1 − (A_f/A₀) × 100 and were compared to Trolox standard curve to express the results as μM Trolox Equivalents.