Plasma concentrations of individual tea catechins after a single oral dose in humans

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Abstract
1. Ten healthy volunteers ingested 1.5 mmole epicatechin gallate (ECg), epigallocatechin (EGC) or epigallocatechin gallate (EGCg) in a randomized crossover design. After deconjugation, catechins in plasma and 24-h urine samples were determined by high-performance liquid chromatography (HPLC). Antioxidant activity was measured in plasma by determining ferric reducing activity (FRAP). 2. The catechin levels in plasma after ingestion were significantly different: EGC rose quickly with a short elimination half-life (t1/2 elim = 1.7 h), ECg was intermediate in rise but slowest in decline (t1/2 elim = 6.9h), EGCg was slowest in rise but intermediate in decline (t1/2 elim = 3.9h). At 24h, EGC and EGCg had returned to base levels, but ECg was still elevated. Peak maximum varied between 1.3 (EGCg) and 5.0 micromol l(-1) (EGC). 3. Very limited interconversion (ECg-->epicatechin, EGCg-->EGC) occurred indicating that degallation is not required for uptake. 4. Up to 13.6% of the ingested EGC (partly methylated) was excreted in the urine, but ECg or EGCg were not detected. 5. EGC and ECg produced an increase in antioxidant activity in plasma, but with EGCg, no statistically significant effect was found. 6. The pattern of uric acid in plasma showed a clear resemblance with that of FRAP and linear regression analysis indicated a very significant relationship (R2 = 0.88, p < 0.0001). 7. It is concluded that tea catechins differ significantly in their pharmacokinetic behaviour.