2.4. Determination of total flavonoid content (TFC) in Senjed peel aqueous extracts
The spectrophotometer assay for the quantitative determination of flavonoid content was carried out as described by Chen et al. (2007). Briefly, the extract (1 mL, 1 mg/mL) was diluted with 1.25 mL distilled water. At zero time, 75 μL 5% NaNO2 were added to the mixture. After 6 min, 150 μL 10% AlCl3 were added. After another 5 min, 1 mL 1 M NaOH were added to the mixture. Immediately, the absorbance of the mixture, pink in color, was determined at 510 nm versus prepared water blank. Total flavonoids of extracts were expressed on a fresh weight basis as mg/100 g catechin equivalents (CAE).