4.6. Total Flavonoids Content (TFC)

To prepare the plant extract, a sample of 0.2 g plant material was homogenized in 10 mL of 96% (v/v) ethanol. Then, the extract was centrifuged at 4500× g for 30 min. The received supernatant was examined. Total flavonoid content (TFC) was determined by the colorimetric assay in accordance with the methodology proposed by Sevket et al. [57]. Into the 10-mL volumetric flask, 4 mL of dH₂O, 100 µL of the plant extract, 0.3 mL of 5% sodium nitrite (NaNO₂) solution and 300 µL of 10% aluminum chloride (AlCl₃) solution were placed. In 6 min, 2 mL of 1-M NaOH solution was added into the flask. The total volume of the liquid in the flask was brought up to 10 mL with dH₂O. Absorption of the reaction mixture was defined at 510 nm using the UV-3600 (Shimadzu, Japan). Total flavonoids content was calculated using a calibration curve and expressed as mg quercetin equivalent (QE) per gram of dry weight (QE g⁻¹ DW).