Intervention studies with
procyanidin (PC)-rich extracts and products such as cocoa and wine suggest protective effects of PC against
cardiovascular diseases. However, there is no consensus on the absorption and metabolism of PC dimers. Interestingly, nothing is known about the absorption of A-type PC. In this study, the absorption and metabolism of purified PC dimers A1 [
epicatechin-(2-O-7, 4-8)-
catechin], A2 [
epicatechin-(2-O-7, 4-8)-
epicatechin], and B2 [
epicatechin-(4-8)-
epicatechin], A-type trimers, a mixture of A1, B2, and a tetrameric A-type, and monomeric
epicatechin were compared by in situ perfusion of the small intestine of rats for 0-30 min. The rats had their bile duct, portal vein, and small intestine cannulated. Unmodified and methylated metabolites were distinguished from their conjugates by differential
beta-glucuronidase treatment. A1 and A2 dimers were absorbed from the small intestine of rats and they were better absorbed than dimer B2. Absorption of the A-type dimers was only 5-10% of that of monomeric
epicatechin. Dimers were not conjugated or methylated in contrast to
epicatechin, which was partly methylated and 100% conjugated. A-type trimers were not absorbed. Furthermore, the presence of tetrameric PC enhanced the absorption of B2 but not that of A1.
Epicatechin, methylated
epicatechin, and their conjugates were not found as metabolites of the PC tested. In conclusion, dimers A1, A2, and B2 are slightly absorbed but are not conjugated or methylated, thus conserving their
biological activity after absorption. Because PC contents of foods are relatively high, dimers may contribute to systemic effects of PC.