Inhibitory Effect of Coumarins and Isocoumarins Isolated from the Stems and Branches of Acer mono Maxim. against Escherichia coli β-Glucuronidase

We isolated eight known secondary metabolites, including two isocoumarins and six coumarins, from the stems and branches of Acer mono Maxim. Their structures were confirmed using nuclear magnetic resonance spectroscopy and by comparing the data to published reports. The inhibitory effects of all compounds (1−8) on Escherichia coli β-glucuronidase were evaluated for the first time using in vitro assays. 3-(3,4-Dihydroxyphenyl)-8-hydroxyisocoumarin (1) displayed an inhibitory effect against β-glucuronidase (IC50 = 58.83 ± 1.36 μM). According to the findings of kinetic studies, compound 1 could function as a non-competitive inhibitor. Molecular docking indicated that compound 1 binds to the allosteric binding site of β-glucuronidase, and the results corroborated those from kinetic studies. Furthermore, molecular dynamics simulations of compound 1 were performed to identify the behavioral and dynamic properties of the protein–ligand complex. Our results reveal that compound 1 could be a lead metabolite for designing new β-glucuronidase inhibitors.