Abstract
The possible beneficial effects of tea consumption have attracted a great deal of attention. Many of the biological effects have been attributed to tea catechins, but the metabolic fate of these compounds is not clear. In the present study, a major metabolite observed in human blood and urine samples after green tea administration was identified as a O-methylated derivative of (−)-epigallocatechin (EGC) by comparison with products from chemical and enzymatic O-methylation of EGC. The structure of this metabolite was elucidated as 4′-O-methyl-(−)-epigallocatechin (4′-O-MeEGC) by 1H and 13C NMR and heteronuclear multiple bond connectivity experiment. The human plasma level of 4′-O-MeEGC reached its peak value within the first 2 h following tea ingestion. Its maximum concentration was 4 to 6 times higher than that of EGC. The half-lives of EGC and 4′-O-MeEGC in the blood were 1.02 ± 0.07 and 4.39 ± 1.14 h, respectively. The amount of 4′-O-MeEGC excreted in urine was about 3 times higher than that of EGC, and 88% of 4′-O-MeEGC was excreted in urine within 8 h. The present structural information and concentration-time profile of this metabolite provide the basis for understanding the biotransformation of EGC and for future elucidation of its biological activities.
Footnotes
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Send reprint requests to: Dr. Chung S. Yang, Laboratory for Cancer Research, College of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Rd., Piscataway, NJ 08854-8020. E-mail: csyang{at}rci.rutgers.edu
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The study was supported by the National Institutes of Health Grant CA 56673.
- Abbreviations used are::
- EGC
- (−)-epigallocatechin
- EGCG
- (−)-epigallocatechin-3-gallate
- EC
- (−)-epicatechin
- ECG
- (−)-epicatechin-3-gallate
- HPLC
- high-performance liquid chromatography
- CEAS
- coulochem electrode array system
- LC/MS
- liquid chromatography/mass spectrometry
- MS/MS
- tandem mass spectrometry
- ESI
- electrospray ionization
- COMT
- catechol-O-methyltransferase
- SAM
- S-adenosyl-l-methionine
- MeEGC
- mono-O-methylated EGC
- tR
- retention time
- Received August 27, 2000.
- Accepted February 22, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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