2.7.2. Ferric reducing antioxidant power (FRAP) assay

Determination of TAC by the FRAP method was performed on a spectrophotometer SF-2000 (OCB «Spectr», Russia) using to the method of Benzie and Strain (Benzie and Strain, 1996) with the author’s modification. The fresh FRAP solution was prepared by mixing 300 mM acetate buffer (pH = 3.6), 10 mM TPTZ (prepared in 40 mM HCl) and 20 mM ferric (III) chloride aqueous solution in the ratio of 10:1:1 (v/v/v). Volumes of 1.45 mL of FRAP reagent and 50 μL of the sample or standard or distilled water for measuring the control sample were added to the tube. The reaction mixture was incubated for 30 min at 37 °C in the dark. Optical density was measured at a wavelength of 594 nm. TAC was determined according to a standard curve using quercetin in the concentration range of 1–0.1 μM. Depending on their activity, the extracts were diluted with distilled water. The TAC of the OHE was expressed in µmol-equiv. quercetin/g raw material, plasma in µmol-equiv. quercetin/L. The TAC of the liver and brain extracts were expressed in µmol-equiv. quercetin/g protein.