Quantifying Flavonoids in Vernonia guineensis

The aluminum chloride colorimetric protocol described by Chang et al. [35 ] served as support to evaluate the total flavonoid contents in the hydroethanolic extract of V. guineensis. A mixture of extract (100 µl and 2 mg/ml), aluminum chloride (50 µl and 1.2%), and potassium acetate (50 µl and 120 mM) introduced into a tube was incubated (room temperature, 30 minutes) and the absorbance was read (415 nm, spectrophotometer). Various concentrations of quercetin (0.015 to 2 mg/ml) were used to plot the standard curve which allowed the calculation of the total flavonoid content in the extract.