Chapter 15
Analytical Methods for the Active Components in Tea Products
Downloaded by PRINCETON UNIV on July 4, 2013 | http://pubs.acs.org Publication Date: December 17, 2001 | doi: 10.1021/bk-2002-0803.ch015
Huizhen Zhang, Long-Ze Lin, Xian-Guo He, and Michael P. Petteruti Research Laboratory of Natural Products, A. M. Todd Company, 150 Domorah Drive, Montgomeryville, PA 18936
The infusion of dried tea leaves is one of the most popular beverages in the world. Most recently, the relationship between tea consumption and prevention of certain forms of human cancer has received a great deal of attention. In order to control the quality and ensure the reliability and repeatability of pharmacological and clinical research, it is necessary to develop validated analytical methods for the qualitative and quantitative analysis of the active components found in tea products. Tea leaves are rich in polyphenols, caffeine, vitamins, and amino acids. These active components in tea products have various physiological and pharmacological functions, such as antioxidative, chemopreventative activity, suppressive effect of uremic toxin formation, prevention of dental caries, etc. This review will mainly focus on the analytical methods used to evaluate the active components in tea products. H P L C , H P L C - M S , spectrophotometry, near-infrared and other methodologies will be reviewed.
Tea is consumed worldwide and ranks only second to water as a beverage. It is prepared from dried leaves of Camellia sinensis (1). Over 300 different
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© 2002 American Chemical Society
In Quality Management of Nutraceuticals; Ho, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.
Downloaded by PRINCETON UNIV on July 4, 2013 | http://pubs.acs.org Publication Date: December 17, 2001 | doi: 10.1021/bk-2002-0803.ch015
215 kinds of tea are now produced, but there are only three general forms of tea: the unfermented green tea, the partially fermented oolong tea and the fermented black tea. Green tea is manufactured from fresh leaf. The polyphenol components during black tea manufacturing have been extensively oxidized into theaflavins, thearubigins, and other oligomer (2). The chemical composition of tea leaves varies greatly depending on their origin, age and the type of processing (5). Table I shows the composition of fresh green tea leaf based on the dry weight (2). Polyphenol compounds are the most significant group of tea components, especially certain catechins, such as (-)-epicatechin gallate (ECG), (-)-gallocatechin gallate (GCG) and (-)-epigallocatechin gallate (EGCG). Recent interest in green and black tea polyphenol compounds has increased due to their antioxidant activities and their possible role in the prevention of cancer and cardiovascular diseases (5-75). In order to find a constituent or a group of tea components that are a measure of tea quality, to optimize the degree of fermentation that offers the best quality of tea, and to correlate the health effects of tea with certain tea components, it is necessary to develop validated analytical methods for the qualitative and quantitative analysis of the active components found in tea products. This review will mainly focus on the analytical methods used to evaluate the active components in tea products, such as high-performance liquid chromatograph (HPLC), gas chromatograph (GC), mass spectrometry (MS), spectrophotometry (UV/VIS), near-infrared spectroscopy (NIRS) and capillary electrophoresis (CE).
Table I. Composition of Fresh Green Tea Leaf in % Dry Weight Polyphenols Methyl xanthines Amino acids Organic acids Carotenoids Volatiles
36 3.5 4 1.5
