Formation and identification of 4'-O-methyl-(-)-epigallocatechin in humans.
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 (1)H and (13)C 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.
Meng
X
X
Laboratory for Cancer Research, Rutgers, The State University of New Jersey, Piscataway 08854-8020, USA.
Lee
M J
MJ
Li
C
C
Sheng
S
S
Zhu
N
N
Sang
S
S
Ho
C T
CT
Yang
C S
CS
D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D021241:Spectrometry, Mass, Electrospray Ionization; D013662:Tea / Q000737:chemistry*
D013662:Tea; D002392:Catechin; C057580:gallocatechol