Epicatechin is the primary bioavailable form of the procyanidin dimers B2 and B5 after transfer across the small intestine

Perfusion of isolated small intestine with the procyanidin dimers B2 and 13 5 extracted from cocoa indicated that both forms of dimer are transferred t o the serosal side of enterocytes but only to a very small extent (< 1% of the total transferred flavanol-like compounds). However, perfusion of dimer mainly resulted in large amounts of unmetabolised/unconjugated epicatechin monomer being detected on the serosal side (95.8%). The cleavage of dimer during transfer seemed to be energy-dependent, requiring an intact cell sys tem, as incubation with jejunal homogenates failed to yield epicatechin. Lo w levels methylated dimer were also detected (3.2%), but no conjugates and metabolites of epicatechin indicating that metabolism of monomer and dimer is limited during dimer cleavage/translocation. The methylation of dimer ma y be by catechol-O-methyltransferase, however, at high concentrations of di mer COMT activity is reduced leading to an inhibition of both monomer and d imer O-methylation. (C) 2001 Academic Press.