Estimation of total flavonoid content in propolis by two complementary colometric methods

Flavonoids, with various biological activities, are considered as key compounds in propolis. In this study, quantitative determinations of flavonoids in propolis were conducted by two complementary colorimetric methods, aluminum chloride method and 2,4-dinitrophenylhydrazine method. Results suggested that the sum of flavonoid contents determined by the above two individual methods may represent the real content of total flavonoids. In this work, six raw propolis samples were investigated and the total contents of flavonoids ranged from 10.38 ± 0.14% to 24.91 ± 0.53%. As for the 12 commercial propolis products examined, the levels of total flavonoids in tinctures were all below 7% and those in powdery products varied from 2.97 ± 0.05% to 22.73 ± 0.72%.