Validation of green tea polyphenol biomarkers in a phase II human intervention trial.
Health benefits of green tea polyphenols (GTPs) have been reported in many animal models, but human studies are inconclusive. This is partly due to a lack of biomarkers representing green tea consumption. In this study, GTP components and metabolites were analyzed in plasma and urine samples collected from a phase II intervention trial carried out in 124 healthy adults who received 500- or 1000-mg GTPs or placebo for 3 months. A significant dose-dependent elevation was found for (-)-epicatechin-3-gallate (ECG) (p<0.001, trend test) and (-)-epigallocatechin-3-gallate (EGCG) (p<0.05, trend test) concentrations in plasma at both 1-month and 3-months after intervention with GTPs. No significant increase of (-)-epicatechin (EC) or (-)-epigallocatechin (EGC) was observed in plasma after GTP intervention. A mixed-effects model indicated significant effects of dose (EGCG) and dose by time interaction (ECG), but not for EC and EGC. Analysis of phase 2 metabolic conjugates revealed a predominance of free GTPs in plasma, up to 85% for EGCG, while a majority of GTPs in urine were sulfated and glucuronidated conjugates (up to 100% for EC and 89% for EGC). These results suggest that plasma ECG and EGCG concentrations are reliable biomarkers for green tea consumption at the population level.
Wang
Jia-Sheng
JS
Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Box 41163, Lubbock, TX 79409-1163, USA. js.wang@ttu.edu
Luo
Haitao
H
Wang
Piwen
P
Tang
Lili
L
Yu
Jiahua
J
Huang
Tianren
T
Cox
Stephen
S
Gao
Weimin
W
D000328:Adult; D015415:Biomarkers / Q000032:analysis*; D002392:Catechin / Q000031:analogs & derivatives / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005260:Female; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000652:urine; D006801:Humans; D008297:Male; D008875:Middle Aged; D010636:Phenols / Q000737:chemistry / Q000494:pharmacology*; D059808:Polyphenols; D015203:Reproducibility of Results; D013662:Tea / Q000737:chemistry*
D015415:Biomarkers; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; D013662:Tea; D006160:Guanosine Triphosphate; D002392:Catechin; C062669:epicatechin gallate