Structure-Dependent Deconjugation of Flavonoid Glucuronides by Human β-Glucuronidase – In Vitro and In Silico Analyses

Abstract

Flavonoid glycosides are extensively metabolized to glucuronidated compounds after oral intake. Recently, a cleavage of quercetin glucuronides by β-glucuronidase has been found. To characterize the deglucuronidation reaction and its structural prerequisites among the flavonoid subtypes more precisely, four flavonol glucuronides with varying glucuronidation positions, five flavone 7-O-glucuronides with varying A- and B-ring substitution as well as one flavanone- and one isoflavone-7-O-glucuronide were analyzed in a human monocytic cell line. Investigation of the deglucuronidation rates by HPLC revealed a significant influence of the glucuronidation position on enzyme activity for flavonols. Across the flavonoid subtypes, the C-ring saturation also showed a significant influence on deglucuronidation, whereas A- and B-ring variations within the flavone-7-O-glucuronides did not affect the enzymes' activity. Results were compared to computational binding studies on human β-glucuronidase. Additionally, molecular modeling and dynamic studies were performed to obtain detailed insight into the binding and cleavage mode of the substrate at the active site of the human β-glucuronidase.

Development of GROMOS-Compatible Parameter Set for Simulations of Chalcones and Flavonoids

“…It is clear from these results that nonspecific torsional parameters may not always reproduce the quantum mechanics energy barriers and minima of a given dihedral, as expected. Although the automated approach is broadly used to treat ligands within ligand–receptor complexes, − uncured torsional parameters may strongly impact the accurate description of the conformational ensemble in free ligand molecular dynamics simulations, within the protein or even on receptors’ conformational activation. To address this issue, new dihedral parameters potentials were generated (Table S1) and tested.…”