title: Bioavailability and antioxidant effect of epigallocatechin gallate administered in purified form versus as green tea extract in healthy individuals.
abstract: Tea polyphenols have strong in vitro antioxidant activity. Due to their limited bioavailability, however, their contribution to in vivo antioxidant activity may depend on the form of administration. A human intervention study was performed to evaluate the bioavailability and antioxidant capacity of (-)-epigallocatechin-3-gallate (EGCG) administered as a single large dose in the form of either purified EGCG or as green tea extract (Polyphenon E). Plasma concentrations of tea polyphenols were determined by high-performance liquid chromatography (HPLC) analysis combined with coulometric array electrochemical detection (ECD). We found no differences in plasma EGCG concentrations and trolox equivalents determined by the trolox equivalent antioxidant capacity assay after administration of either form of EGCG. However, we found that the plasma antioxidant activity was significantly affected by changes in the plasma urate concentration, which may have interfered with the effect of tea polyphenols on the antioxidant activity. In addition, lymphocyte 8-hydroxydeoxyguanosine to deoxyguanosine (8-OHdG/10(6)dG) ratios were determined by HPLC with ECD. The 8-OHdG/10(6)dG ratios did not change significantly during the 24 h following both EGCG interventions but correlated significantly within individuals determined during the two interventions separated by 1 week. In summary, changes in plasma uric acid due to dietary intake were significantly correlated to the plasma antioxidant activity and exerted a stronger influence on the plasma antioxidant activity compared with the EGCG intervention. In future studies of dietary effects on the plasma antioxidant capacity, changes in plasma uric acid will need to be closely monitored.
authors.affiliation: Center for Human Nutrition, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA. shenning@mednet.ucla.edu
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Henning
authors.forename: Yantao
authors.initials: Y
authors.lastname: Niu
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: Nicolas H
authors.initials: NH
authors.lastname: Lee
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Hara
authors.forename: Gail D
authors.initials: GD
authors.lastname: Thames
authors.forename: Rosario R
authors.initials: RR
authors.lastname: Minutti
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Carpenter
authors.forename: Hejing
authors.initials: H
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Heber
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine / Q000031:analogs & derivatives; D000975:Antioxidants / Q000494:pharmacology*; D001682:Biological Availability; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry; D004249:DNA Damage; D003849:Deoxyguanosine / Q000032:analysis; D044948:Flavonols / Q000097:blood; D006147:Guanine / Q000031:analogs & derivatives / Q000032:analysis; D006801:Humans; D008214:Lymphocytes / Q000737:chemistry; D013662:Tea / Q000737:chemistry*; D014527:Uric Acid / Q000097:blood
chemical_list: D000975:Antioxidants; D044948:Flavonols; D013662:Tea; D014527:Uric Acid; D006147:Guanine; C078307:8-oxo-7,8-dihydrodeoxyguanine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D002392:Catechin; D004247:DNA; C045651:epigallocatechin gallate; D003849:Deoxyguanosine; C472086:polyphenon E