Total flavonoid content

The total flavonoid content was measured using an aluminum chloride colorimetric assay as described by Park et al.²⁵ In a 10-mL test tube, 0.3 mL of extracts, 3.4 mL of 30% methanol, 0.15 mL of NaNO₂ (0.5 M), and 0.15 mL of AlCl₃.6H₂O (0.3 M) were mixed thoroughly. After a few min, 1 mL of NaOH (1 M) was added. In the same way, the standard solution was also prepared using rutin (Ru) as a standard. The standard curve for total flavonoids was made using a Ru standard solution (10, 20, 30, 40, 50 and 60 µg/mL). The solution was mixed well and the absorbance was measured against the reagent blank at 506 nm. The total flavonoids were expressed as mg of Ru equivalent/g of dried extract.