Catechins in tea

There are four main theaflavins common to black teas, and a second group of minor theaflavins, including the isotheaflavins (55) and neotheaflavins (57) (Table 5). The total theaflavin concentration in black tea leaves does not usually exceed 2% and can be as low as 0.3%. At most, only 10% of the catechins in tea flush can be accounted for as theaflavins in black tea and the fate of the remaining catechins is less clear. Theaflavins can be readily determined by direct hplc analysis of tea beverages (48,58,59). 

BRONNER w E and BEECHER G R (1998) Method for determining the content of catechins in tea infusions by high-performance liquid chromatography , J Chromatogr A, 805, 137-42. 

ZEEB D J, NELSON B c, ALBERT K and DALLUGE J J (2000) Separation and identification of twelve catechins in tea using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry , Chem, 72, 5020-26. 

Another simple and reliable RP-HPLC method was developed for the determination of catechins in tea leaves and tea extracts. 

A slightly different RP-HPLC technology has been developed and applied for the determination of catechins in tea infusions. Tea infusions were prepared by the traditional method, — filtered and used for HPLC analysis. Separation was carried out in an ODS column... 

D. Stach and O.J. Schmitz, Decrease in concentration of free catechins in tea over time determined by micellar electrokinetic chromatography. J. Chromatogr.A 924 (2001) 519-522. 

The concentration of individual catechins in tea flush are shown in Table V. The most abundant catechin is (-)-epigallocatechin gallate. 

D.J. Zeeb, B.C. Nelson, K. Albert, J.J. Dalluge, Separation and identification of twelve catechins in tea using LC-APCI-MS, Anal. Chem., 72 (2000) 5020. 

Capillary electrophoresis (CE) is an emerging analytical technique for determination of catechins. The majority of CE studies involve the analysis of catechins in tea infusion, extracts as well as supplements. The three variants of CE suitable for the analysis of catechins include capillary zone electrophoresis (CZE), micellar electro-kinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC) with UV detection. In general, the resolution of MEKC was found to be superior to CZE for separation of catechins. MEEKC is a relatively new technique, and the few reports available suggest that it offers a performance similar to MEKC. CE conditions are often quite complex, and many factors, such as buffer composition, pH, presence of surfactants, and column temperature, can all affect the quality of separation and should be optimized individually. On the other hand, CE offers several advantages over HPLC. The short analysis time (<20 minutes), low running costs, and reduced use of solvents make it an attractive alternative for routine analysis of catechins. 

Poon, G. K. 1998. Analysis of catechins in tea extracts by liquid chromatography electrospray ionization mass spectrometry. J. Chromatogr. A 794 63-74. 

Zhn, X. L., Chen, B., Ma, M., Lno, X. B., Zhang, R, Yao, S. Z., Wan, Z. T., Yang, D. J., and Hang, H. W. 2004. Simnltaneons analysis of theanine, chlorogenic acid, pnrine alkaloids and catechins in tea samples with the help of mnlti-dunension information of on-line high performance liqnid chromatography/electrospray-mass spectrometry. J. Pharm. Biomed. Anal. 34 695-704. 

Tea and its constituents have been shown to be beneficial in several inflammatory disorders. The catechins in tea, particularly epigallocatechin gallate (EGCG), have been shown to inhibit inflammation by modulating several pathways. Tea and its constituents have been shown to be effective against several inflammatory conditions, such as osteomyelitis, psoriasis, arthritis," and inflammation of the respiratory system." -" ... 

The catechins in tea occur mainly in the form of 3-galloyl esters such as catechin-3-gallate (XVI). 

Suzuki, T., Yamazaki, N., Sada, Y., Oguni, I. Moriyasu, Y. (2003). Tissue distribution and intracellular localization of catechins in tea leaves. Bioscience, Biotechnology, and Biochemistry, 67, 2683-2686. 

The inhibitory activity of tea constituents against tumorigenesis has been demonstrated in many studies with animal models (7). Nevertheless, the molecular mechanisms of such inhibition are not clearly understood. Many investigators have used cell lines to elucidate the biological activities that may be related to the inhibition of carcinogenesis and shown that EGCG, the major catechin in tea, has the following activities (reviewed in (7)) ... 

Previous studies from other laboratories have demonstrated that the hypocholesterolemic effect of tea is due to tea catechins by decreasing the micellar solubility and intestinal absorption of dietaiy cholesterol (5). EGCG is the major catechin in tea leaves to inhibit the absorption of exogenous cholesterol from digestive tract. Moderate enhancement in the elimination of endogenous cholesterol by tea catechins has been reported (9). A previous study has demonstrated that Pu-Erh tea reduces plasma cholesterol and triacylglycerol... 

Novdkovd et al. described a UHPLC-DAD method for the simultaneous determination of twenty-nine phenolic acids, flavonoids, and catechins in tea samples using BEH C18 columns and waters and acidified acetonitrile as the mobile phase... 

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