2.3.7. Measurement of total flavonoid content
The solvent used to extract flavonoids in the sample was 80% v/v
methanol in distilled water. Flavonoids in a four gram sample were extracted
in 20 mL of solvent by shaking for 2 h at 25 °C followed by a centrifugation
at 12,000 rpm at 4 °C. Total flavonoid content (TFC) was
estimated in the supernatant according to the assay described by
Hossain and Rahman (2011). The results were compared against a calibrated
curve drawn between absorbance and different concentrations
of quercetin solution and expressed as quercetin equivalent (QE) in
100 g of sample.