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Journal of Food and Drug Analysis, Vol. 10, No. 3, 2002, Pages 178-182
Estimation of Total Flavonoid Content in Propolis by Two Complementary Colorimetric Methods
CHIA-CHI CHANG1, MING-HUA YANG2*, HWEI-MEI WEN1 AND JIING-CHUAN CHERN1
1. Department of Food Science, National Pingtung University of Science and Technology (NPUST), 1 Hseuh-Fu Road, Neipu Hsiang, Pingtung Hsien 912, Taiwan, Republic of China2. Department of Food and Nutrition, Hung-Kuang Institute of Technology, 34 Chung-Chi Road, Shalu, Taichung Hsien 433, Taiwan, Republic of China
(Received: January 25, 2002; Accepted: May 16, 2002)
ABSTRACT
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%.
Key words: Propolis, flavonoids, flavones, flavonols, flavanones, flavanonols, quantitative determination, colorimetric method, aluminum chloride reaction, 2,4-dinitrophenylhydrazine reaction
INTRODUCTION
Propolis, the material used by bees to protect their hives, is a glue-like substance composed of plant resins, bee waxes and pollens. Since various biological activities of propolis such as antibacterial, antiviral, anti-inflammatory and anaesthetic properties were found(1-3), it is used as a health food. The chemical composition of propolis is quite complicated and over 150 components have been identified(2,4). Among these compounds flavonoids were suggested to be responsible for the biological activities(5,6).
Therefore, the content of flavonoids is considered as an important index for evaluating propolis quality.
The analysis of flavonoids in propolis has been done by colorimetric methods(7-10), thin layer chromatography(9,11), gas chromatography(12,13), gas chromatography-mass spec-trometry(14-16) and high performance liquid chromatography(7,15,17,18). Although chromatographic techniques in combination with absorption spectrum analysis and mass spectrometry provide definitive information for identification and quantification of flavonoids in propolis, these methods usually require advanced instruments, various authentic standards and are time-consuming. On the other hand, colorimetric methods targeting flavonoids of...