BLOOD AND URINE LEVELS OF TEA CATECHINS AFTER INGESTION OF DIFFERENT AMOUNTS OF GREEN TEA BY HUMAN VOLUNTEERS

The inhibitory activity of tea against tumorigenesis has been demonstr ated in many animal models and has been suggested by some epidemiologi cal studies, Such activity has generally been attributed to tea catech ins, To understand the bioavailability of tea catechins in humans, we gave 18 individuals different amounts of green tea and measured the ti me-dependent plasma concentrations and urinary excretion of tea catech ins, After taking 1.5, 3.0, and 4.5 g of decaffeinated green tea solid s (dissolved in 500 mi of water), the maximum plasma concentration (C- max) of (-)-epigallocatechin-3-gallate (EGCG) was 326 ng/ml, the C-max of (-)-epigallocatechin (EGC) was 550 ng/ml, and the C-max of (-)-epi catechin (EC) was 190 ng/ml These C-max values, were observed at 1.4-2 .4 h after ingestion of the tea preparation, When the dosage was incre ased from 1.5 to 3.0 g, the C-max values increased 2.7-3.4-fold, but i ncreasing the dose to 4.5 g did not increase the C-max values signific antly, which suggested a saturation phenomenon, The half-life of EGCG (5.0-5.5 h) seemed to be higher than the half-life of EGC or EC (2.5-3 .4 h), EGC and EC, but not EGCG, were excreted in the urine, Over 90% of the total urinary EGC and EC was excreted within 8 h, When the tea dosage was increased, the amount of EGC and EC excretion seemed to inc rease, but a clear dose-response relationship,vas not observed, The pr esent study provides basic pharmacokinetic parameters of green tea cat echins in humans; these parameters may be used to estimate the levels of these compounds after drinking tea.