3.6. Total Phenolic Content and DPPH Radical Scavenging Activity

The total phenolic content (TPC) was determined according to the Folin–Ciocalteu colorimetric method, with gallic acid (GA) as a standard. The samples (1 g) were extracted with methanol/water 80:20 (10 mL) for 2 h at an ambient temperature and were filtered (Whatman Nr 1, Whatman International, Maidstone, UK). A 300 µL extract was added to 1.5 mL diluted Folin–Ciocalteu reagent, with 1.5 mL of sodium carbonate being added after 5 min; after 90 min of incubation, absorbance was read at 725 nm with 80% methanol as a reference, and the results were expressed as mg gallic acid equivalents (GAE)/100 g d. m.

DPPH radical scavenging activity of sample solutions was estimated using the stable radical DPPH. The methanol DPPH solution (3.9 mL) was added to the extract (200 µL), shaken vigorously, and allowed to stand in the dark for 30 min. The control sample was prepared using 80% methanol instead of the sample. The absorbance of the reaction mixtures was read at 517 nm, and scavenging activity was calculated according to Equation (1), as follows:

Both methods are described in detail by Wang and Ryu [10].