Mechanistic insights into Helicobacter pylori urease inhibition by poplar propolis ethanol extract

Propolis, a resinous mixture from plant exudates, is widely used in traditional ethnomedicine for gastrointestinal infections, implying anti-Helicobacter pylori (H. pylori) potential. However, its molecular mechanisms targeting H. pylori urease (HPU), a key virulence factor, remain unclear.

This study aimed to characterize the inhibitory activity and kinetic properties of poplar propolis ethanol extract (PPEE) against HPU and jack bean urease (JBU), and to elucidate the underlying molecular mechanisms.

UPLC-MS/MS-based metabolomics was used to identify PPEE's potential bioactive candidates. Enzyme activity assays, kinetic analysis, thiol/Ni²⁺ protection assays, transcriptional profiling of urease-related genes, and molecular docking were applied for mechanistic exploration. Bacterial growth curve assays and PI staining verified its antibacterial activity.

PPEE, enriched in flavonoids and phenolic acids, exhibited significant dose-dependent and reversible inhibition on HPU, with superior potency to JBU. Mechanistically, PPEE acted synergistically by competitively binding to HPU's substrate pocket, disrupting thiol-Ni²⁺ coordination, inducing slow-binding conformational stabilization, and perturbing tertiary structure. It also downregulated ureA/ureB, nixA, and ureH/ureI, forming a multi-layered mode of "direct enzyme inhibition + blocking synthesis/assembly". Urease inhibition was the core anti-H. pylori mechanism, with auxiliary urease-independent activity. Molecular docking confirmed stable interactions between PPEE components and HPU's active center/substrate pocket. Experimental validation showed that quercetin and taxifolin inhibited HPU in a dose-dependent manner.

PPEE specifically inhibits HPU via multi-targeted synergistic mechanisms, providing molecular evidence for propolis-derived anti-H. pylori agents and laying a foundation for subsequent SAR and in vivo studies.