*2.6. Assessment of Antioxidant Activity by Radical Scavenging Assay: DPPH and ABTS*

The radical scavenging capacity of the bee pollen extracts was determined based on the scavenging ability of the antioxidants towards the stable 2, 2-diphenyl-1-picrylhydrazyl radical known as DPPH method [24]. The scavenging activity on pollen extracts, mixed with 2.7 mL of a DPPH solution (6 × <sup>10</sup>−<sup>5</sup> M) was measured. The pollen sample solution and the blank-DPPH solution were incubated at room temperature for 30 min in the dark. The absorbance with a UV–vis spectrophotometer was measured at 517 nm.

The radical scavenging activity by ABTS assay was determined according to a method reported by Re et al. [25]. The ABTS solution was prepared by reacting ABTS 7 mM in water with 2.45 mM potassium persulfate. ABTS stock solution was left at room temperature for 12–16 h in the dark until it reached a stable oxidative state. ABTS stock solution was prepared by dilution with ethanol to give an absorbance of 0.70 ± 0.02 at 734 nm. Then, 980 μL of this solution was mixed with 20 μL of the ethanolic extract of bee pollen sample and finally, the absorbance was measured at 734 nm.

The antioxidant activity of bee pollen samples was expressed as percentage of DPPH and ABTS calculated using the following equation: Scavenging activity (%) = [(AbsB−AbsS)/ AbsB] × 100, where AbsB is the absorbance of the blank solution according to radical used and AbsS is the absorbance of the pollen extract solution.
