The metabolism and excretion of 3-palmitoyl-(+)-catechin in the rat

Abstract

1. Oral administration of 3-palmitoyl-(+)-[U-¹⁴C]catechin to rats resulted in the excretion of 63% of the dose in urine, 24% in faeces and 7% as ¹⁴CO₂ in the 17 days following dosing. Persistent levels of ¹⁴C were noted in tissues, and 28 days after dosing 3.7% of the dose was present in the animal body.

2. Biliary excretion accounted for 28.2% of the dose in 48h after dosing. The major biliary metabolite was 3′-O-methyl-(+)-catechin glucuronide. These experiments also demonstrated the dependence of 3-palmitoyl-(+)-catechin on the presence of bile in the intestine for absorption.

3. Studies in vitro showed that intestinal micro-organisms were unable to metabolize 3-palmitoyl-(+)-catechin. The compound did, however, undergo deesterification in plasma and also in liver-perfusion studies. In the latter experiments, conjugates of the liberated (+)-catechin were also formed.

4. Urinary metabolites were predominantly (80%) conjugates of (+)-catechin and 3′-O-methyl-(+)-catechin. Ring scission products and ¹⁴CO₂ were also excreted but not from rats with ligated bile ducts. These metabolites are therefore considered to arise from biliary metabolites not containing the ester linkage.