FRAP Assay

The antioxidant power of ferric ion reduction is based on the mechanism of single electronic transfer. The sample was treated according to [19], with minor modifications. FRAP reagen<sup>t</sup> was prepared by mixing 100 mL of 0.3 M acetate buffer (pH 3.6) (Sigma-Aldrich Chemie GmbH, Darmstadt, Germany), 10 mL of 10 mM 2,4,6-tripyridyl-s-triazine (TPTZ) in 40 mM HCl (Merck KGaA, Darmstadt, Germany) and 10 mL of 20 mM FeCl3·6H2O (Merck KGaA, Darmstadt, Germany) in distilled water. The reaction was carried out by mixing 3.0 mL of FRAP reagen<sup>t</sup> with 0.1 mL of the studied extract. The reaction time was 10 min at 37 ◦C in the dark and the absorbance was measured at a wavelength of 593 nm by a VIS spectrophotometer Camspec M107 (Spectronic-Camspec Ltd., Leeds, the United Kingdom) versus a control sample prepared with methanol (Merck KGaA, Darmstadt, Germany). The antioxidant activity is expressed in mM Trolox® equivalents (TE) per g dry weight.
