Formation and identification of 4 '-O-methyl-(-)-epigallocatechin in humans

The possible beneficial effects of tea consumption have attracted a great d eal of attention, Many of the biological effects have been attributed to te a catechins, but the metabolic fate of these compounds is not clear, In the present study, a major metabolite observed in human blood and urine sample s after green tea administration was identified as a O-methylated derivativ e of (-)epigallocatechin (EGC) by comparison with products from chemical an d enzymatic O-methylation of EGG. The structure of this metabolite was eluc idated as 4'-O-methyl-(-)-epigallocatechin (4'-O-MeEGC) by H-1 and C-13 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 t ea ingestion, Its maximum concentration was 4 to 6 times higher than that o f EGG. 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 ur ine was about 3 times higher than that of EGG, and 88% of 4'-O-MeEGC was ex creted in urine within 8 h. The present structural information and concentr ation-time profile of this metabolite provide the basis for understanding t he biotransformation of EGC and for future elucidation of its biological ac tivities.