*4.7. Total Phenolic Compounds and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) Radical-Scavenging Activity*

First, 1 g FW of sample was homogenized in a solution containing 50% acetone and 50% water (1:10). The samples were vortexed and incubated for 15 h at 20 ◦C. Then, 100 µL of supernatant was mixed with 0.5 mL of Folin–Ciocâlteu reagent (Sigma-Aldrich, Italy) and 6 mL of distilled water. Next, 1.5 mL of Na2CO<sup>3</sup> (20%) was added, before incubating at 20 ◦C for 2 h. The absorbance was read at 765 nm. The concentration of total phenolic compounds was calculated as a function of the values obtained from the gallic acid standard curve (0, 50, 100, 250, and 500 mg·L −1 ) (*R* <sup>2</sup> = 0.9954). The total phenolic content was expressed as mg·100 g−<sup>1</sup> gallic acid equivalent.

The antioxidant activity was determined using DPPH. About 1 g of fresh weight was mixed with 1.5 mL of methanol solution (80%), sonicated for 30 min, and centrifuged (10 min, 5 ◦C, 5000× *g*). Then, 0.01 mL of supernatant was mixed with 1.4 mL of 150 µM DPPH solution in methanol and water (95:5), before incubating for 30 min in the dark. The sample was read at 517 nm. The antioxidant activity was calculated as a function of the values obtained from the Trolox standard curve (0 to 0.5 mg·mL−<sup>1</sup> ) (*R* <sup>2</sup> = 0.9995). DPPH scavenging activity values were expressed as Trolox equivalent antioxidant activity (mg TE·100 g−<sup>1</sup> ).
