Determination of Total Flavonoid Contents

Total flavonoid contents (TFC) were determined by using aluminum chloride colorimetric method.¹⁸ Briefly, 0.25 mL of extract (31.25-250 mg/mL) was added into 0.75 mL distilled water, followed by the addition of 0.15 mL of sodium nitrite solution (5%). After 5 min incubation period, 0.3 mL aluminum chloride (10%) was added Followed by another round of 5 min incubation, 1 mL of 1 M aqueous sodium hydroxide solution was added. The mixture was shaken gently. The absorbance of the mixture was noted at 510 nm in triplicate. The results were expressed in term of mg of catechin/g DW of extract.