Total flavonoid content
The total flavonoid content (TFC) was assayed as described by
Zhishen et al.15 In brief, 0.5 mL of herbal tea infusion was mixed
with 2 mL of distilled water and 0.15 mL of 20% w/v sodium
nitrite and was left to stand for 5 min. Then 0.3 mL of 10% w/v
aluminium chloride was added to this mixture. After 6 min, 2 mL
of 1 mol L−1 sodium hydroxide and 0.2 mL of distilled water were
added. The absorbance was read at 510 nm. The results were
expressed as mg g−1 quercetin equivalents (QE). Measurements
were performed in triplicate