A comparison of the in vitro biotransformation of (–)‐epicatechin and procyanidin B2 by human faecal microbiota

Abstract

The catabolism by human faecal microbiota of (-)-epicatechin (1) (2, 3-cis stereochemistry) and its dimer pure procyanidin B2 (2), has been compared using a static in vitro culture model. The catabolites were characterised by LC-MS(n), UV absorption and relative retention time, and quantified relative to standards. No more than approximately 10% of procyanidin B2 (2) was converted to epicatechin (1) by scission of the interflavan bond. Five phenolic acid catabolites (M(r)<290) were unique to 2, and ten phenolic acid catabolites (M(r)<290) were common to both substrates. The dominant catabolites (> or =24 h incubation) were 5-(3'-hydroxy phenyl) valeric acid (9), 3-(3'-hydroxyphenyl) propionic acid (10) and phenyl acetic acid (12) (maximum yields 27.4+/-4.2, 38.2+/-4.2, 22.7+/-2.9%, respectively, from 1 and 9.4+/-1.2, 52.8+/-2.1, 28.8+/-1.6%, respectively, from 2). Substrate 2 was degraded twice as rapidly as 1. Evidence is presented for the production of previously unreported catabolites of 2 that retain the flavanol A-ring and the C4-->C8 interflavan bond. It was confirmed that catabolism favoured removal of the 4'-hydroxyl rather than the 3'-hydroxyl group and that both beta-oxidation and alpha-oxidation occurred.

In Vivo Bioavailability, Absorption, Excretion, and Pharmacokinetics of [14C]Procyanidin B2 in Male Rats

“…In addition, the 8-fold larger V d calculated from the total 14 C after oral dosing (higher or lower), compared with the intravenous dosing, indicates that some of the compounds formed after the oral dosing are comparatively more hydrophobic than the parent compound. This observation is consistent with previous findings (Stoupi et al, 2009) that the gut flora metabolites produced in an in vitro model of procyanidin B2 catabolism have greater retention times (14.06 -22.71 min) compared with the substrate (13.53 min) during reversed-phase high-performance liquid chromatography.…”

“…In this regard, it is interesting to note that after a single oral dose of (Ϫ)-[3-3 H]epicatechin (4.5 mg/kg), rats excreted 2.9 and 90.3% of the total radioactivity in urine and feces, respectively, and the bioavailability was 7.8% calculated from the U ϱ values (Catterall et al, 2003). This behavior is in marked contrast to that observed with [ 14 C]procyanidin B2 and also suggests that in the present study little if any of the procyanidin was metabolized to an intermediate monomer, consistent with previous reports (Stoupi et al, 2009). In the present study, C max increased in proportion with the oral dose, the value for group II being twice that of group III (Table 2), thus providing no evidence for saturation at least at these two doses and suggesting linear first-order elimination at such doses.…”

“…However, the maximal concentrations (C max ) for total 14 C in blood were not attained until 5 to 6 h after oral administration, suggesting that much of the radioactivity was absorbed from the distal part of the small intestine and/or the colon. Taken collectively, these data strongly suggest that much of the radioactivity detected in the blood after oral administration is derived from low molecular weight phenolic acids and other compounds produced from procyanidin B2 by microorganisms in the gut before absorption, as has been previously shown for procyanidin B3 by rat cecal microflora (Gonthier et al, 2003b), crude proanthocyanidins by human colonic microflora (Déprez et al, 2000), and procyanidin B2 by human colonic microflora (Stoupi et al, 2009) …”

Role of the small intestine, colon and microbiota in determining the metabolic fate of polyphenols

“…by live microbiota are not observed with microbiota inactivated by chloroform suggesting that enzymes released from dead cells were not responsible [130,131], and implying that uptake mechanisms for the test substance were available to at least some of the organisms present. Escherichia coli and Bifidobacterium bifidum can, under anaerobic conditions, take up quercetin much more efficiently than either rutin or quercetin-3-O-glucoside, and B.…”

Polyphenols in lahpet-so and two new catechin metabolites produced by anaerobic microbial fermentation of green tea

“…Compounds 4-6 were reported to be metabolites of catechins and proanthocyanidins produced by mammalian intestinal bacteria [6,7,11,12]. Pyrogallol (3) is considered to be produced by degradation of gallic acid [9,10], while the three diphenylpropane derivatives are reduction products of 2, 3, and (−)-epiafzelechin.…”