Metabolomic profiles of A-type procyanidin dimer and trimer with gut microbiota in vitro

Although intestinal microbiota plays an important role in the metabolism of procyanidins, the microbial metabolic pathway of A-type procyanidins remains elusive. In this study, A-type dimer procyanidin A1 [EC-(2β-O-7,4β-8)-C] and trimer PPD [EC-(4β-6)-EC-(2β-O-7,4β-8)-C] were incubated with rat faecal microbiota in vitro, and their metabolomic profiles were analyzed by UPLC-QTOF/MS. Multivariate statistical analysis identified 24 and 30 discriminant metabolites for A1 and PPD, respectively. The C-ring opened catabolites of procyanidin A1 and PPD and the typical phenolic acid metabolites were identified, including phenylacetic acid, (4′-hydroxyphenyl)acetic acid, 3-phenylpropanoic acid, 3-(4′-hydroxyphenyl)propanoic acid, 3-(3′,4′-dihydroxyphenyl)propanoic acid, and 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone. Notably, procyanidin A1 and (epi)catechin were identified from the metabolites of PPD; however, no (epi)catechin was found in the metabolites of procyanidin A1, indicating that the faecal microbiota can destroy B-type linkage (C4-C6 interflavan bond) but not A-type linkage (C4-C8 and additional C2-O-C7 interflavan bond) in the metabolism of A-type procyanidins