Oral absorption and bioavailability of tea catechins.
The absorption characteristics and oral bioavailability of three tea catechins, namely (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), were assessed in this study. Male Sprague Dawley rats (210-230 g) received either an intravenous (i.v. 50 mg/kg) or oral (5000 mg/kg) dose of decaffeinated catechin-fraction containing EC (5%), EGCG (50%), and ECG (13%). Concentrations of the compounds in plasma, urine, and feces were measured using HPLC. A non-compartmental approach was employed for pharmacokinetic analysis. Results indicated that maximum plasma concentrations for the catechins (15-112 micrograms/ml) were achieved at 2 h post-oral dosing and the apparent volume of distribution (Vd/F) ranged from 30 to 63 l/kg. Absolute bioavailability (F) of EC, EGCG, and ECG was assessed to be 0.39, 0.14, and 0.06, respectively. Estimates of terminal elimination half-life (t1/2, lambda z) of the catechins after oral dosing were 451-479 min and were 1.4-10 fold longer than those observed for the i.v. dosing. The discrepancy in terminal elimination and low rate and extent of absorption indicated the possibility of flip-flop kinetics. Respective urinary recoveries were 0.17-4.72% and 2.11-14.2% after oral and i.v. dosing. In conclusion, the low systemic availability of tea catechins observed could be a result of slow absorption, high first pass effect, and wide tissue distribution.
Zhu
M
M
Department of Pharmacy, Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
Chen
Y
Y
Li
R C
RC
D000042:Absorption; D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002392:Catechin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics* / Q000652:urine; D002851:Chromatography, High Pressure Liquid; D007275:Injections, Intravenous; D008297:Male; D009061:Mouth Mucosa / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013662:Tea / Q000737:chemistry*
D013662:Tea; D002392:Catechin; C062669:epicatechin gallate; C045651:epigallocatechin gallate