4.3. Determination of Antioxidant Activity by DPPH Test

The determination of the antioxidant activity by the DPPH method was carried out according to the procedure developed by Yang et al. [38]. A solution of the DPPH radical (2,2-diphenyl-1-picrylhydrazyl) was prepared by dissolving 27.8 mg of DPPH in 200 mL of 80% methanol. In order to perform the spectrophotometric test, 100 μL of the examined extract and 900 μL of DPPH solution were mixed. The mixture was left for 16 min at room temperature. The absorbance at 515 nm was measured with a FLUOstar OMEGA BGM LAB Tech spectrophotometer (Ortenberg, Germany) against the reagent test. The reagent sample contained distilled water instead of the tested extract. The antioxidant activity of the tested samples was expressed in µM of Trolox/100 g of product, against the standard curve prepared for the Trolox solution.