<i>In vitro</i> production of (+)-catechin and (−)-epicatechin glucuronides to better understand the <i>in vivo</i> metabolism of a polyphenol-rich extract (Memophenol™)

Consumption of (+)-catechin and (-)-epicatechin is associated with beneficial effects on human health. However, their limited systemic circulation in native form suggests that their metabolites may contribute to these effects. The aim of this study was to produce and structurally characterize glucuronide metabolites of (+)-catechin and (-)-epicatechin, which are not commercially available, and to assess their presence in plasma from volunteers who consumed a blend of grape and wild blueberry extracts. Firstly, four monoglucuronides of each flavanol were produced using rat liver microsomes and characterized by UHPLC-DAD-MS/MS and NMR. Using these compounds, we were able to confirm the presence in human plasma of three glucuronides: one known (-)-epicatechin glucuronide and two previously unidentified (+)-catechin glucuronides. Further research is needed to understand their biological role.