T. Kohri et al., Synthesis of (-)-[4-H-3]epigallocatechin gallate and its metabolic fate inrats after intravenous administration, J AGR FOOD, 49(2), 2001, pp. 1042-1048
Because a great deal of attention has been focused on the metabolism of (-)
-epigallocatechin gallate (EGCg), quantitative analysis of this compound is
required. For this purpose we developed a method of chemical synthesis of
[4-H-3]EGCg. Synthesized [4-H-3]EGCg showed 99.5% radiochemical purity and
a specific activity of 13 Ci/mmol. To clarify the excretion route of EGCg,
the radioactivity levels of bile and urine were quantified after intravenou
s administration of [4-H-3]EGCg to bile-duct-cannulated rats. Results showe
d that the radioactivity of the bile sample excreted within 48 h accounted
for 77.0% of the dose, whereas only 2.0% of the dose was recovered in the u
rine. The excretion ratio of bile to urine was calculated to be about 97:3.
These results clearly showed that bile was the major excretion route of EG
Cg. Time-course analysis of the radioactivity in blood was also performed t
o estimate the pharmacokinetic parameters following intravenous administrat
ion of [4-H-3]EGCg. In addition, EGCg metabolites excreted in the bile with
in 4 h after the intravenous dose of [4-H-3]EGCg were analyzed by HPLC. The
results showed that 4',4"-di-O-methyl-EGCg was present in the conjugated f
orm and made up about 14.7% of the administered radioactivity.