Procyanidin Dimers A1, A2, and B2 Are Absorbed without Conjugation or Methylation from the Small Intestine of Rats

Abstract

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.

Polymeric proanthocyanidins from Sicilian pistachio (Pistacia vera L.) nut extract inhibit lipopolysaccharide-induced inflammatory response in RAW 264.7 cells

“…Since only flavonol monomers and dimeric proanthocyanidins are absorbed [58][59][60][61], systemic effects of proanthocyanidins would be limited to these compounds or eventually to not yet characterized metabolites and/or colonic degradation products from the polymeric molecules [58]. In this context, our findings cannot help to rationalize the cardiovascular protection nor provide a molecular interpretation for the anti-inflammatory effects of pistachio nut diets [20].…”

Possible Evidence of Contamination by Catechins in Deconjugation Enzymes fromHelix pomatiaandAbalone entrails

“…To understand the beneficial biological activities of catechins, a tremendous amount of research has examined the absorption and metabolism of catechins, and deconjugation enzymes are often used in the experiments. [18][19][20] However, there is no report demonstrating that catechins were present in the deconjugation enzymes. This may be because in those studies, they dealt with the application C 3 10 5 10 EC 3 10 5 10 GC 3 10 5 10 EGC 3 10 5 10 Cg 3 10 2 5 ECg 3 10 2 5 GCg 3 10 5 10 EGCg 3 10 5 10 The detection limit was a signal-to-noise ratio of more than 3:1, and the quantification limit was a signal-to-noise ratio of more than 10:1.…”

Effects of Peanut-Skin Procyanidin A1 on Degranulation of RBL-2H3 Cells

“…It is thus likely that high-molecular-weight and low-molecular-weight polyphenols inhibit cell degranulation by different mechanisms. Since it has been reported that only low-molecular-weight polyphenols, epicatechin, procyanidin A1, A2, and B2, can be absorbed in the digestive tract, 22) and only partially, our study focused on the PSEL fraction to clarify its inhibitory mechanism against degranulation.…”