Phenolic compounds from the stems of Zanthoxylum piperitum and their inhibition of β-glucuronidase: Enzyme kinetics, molecular docking, and molecular dynamics analysis

Zanthoxylum piperitum, commonly known as Japanese pepper, is a versatile plant from the Rutaceae family that has attracted significant scientific research interest due to its culinary and medical applications. Herein, we present a phytochemical investigation of Z. piperitum stems, leading to the isolation and characterization of a new compound, zanthopiperitol (1), along with four known phenolic compounds (2–5). Among them, ailanthoidiol (2) demonstrated potent β-glucuronidase inhibition with an IC₅₀ of 68.39 ± 2.29 µM. The results of an enzyme kinetics analysis suggest that it acts as a competitive inhibitor of β-glucuronidase while molecular docking simulation outcomes reveal that it can bind effectively to key amino acid residues in the main catalytic binding site of β-glucuronidase. Moreover, the strong stability of compound 2 bound to the enzyme binding site is indicated via a 100-ns molecular dynamics simulation study. This study highlights the potential of exploiting naturally occurring β-glucuronidase inhibitors such as ailanthoidiol for treating various gastrointestinal health issues.