Phytochemical Constituents and Antibacterial Activities of Leaf and RootExtracts from Tetrastigma hemsleyanum Diels et Gilg

Introduction: Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is widely used in traditional Chinese medicine for its anti‑inflammatory effects, but its phytochemical makeup and antibacterial mechanisms remain underexplored. This study investigates the extract’s ability to inhibit growth and quorum-sensing-regulated virulence in Escherichia coli and Pseudomonas aeruginosa, aiming to position T. hemsleyanum as a potential natural antimicrobial. Methods: UPLC-ESI-Q-TOF-MS profiling identified key antibacterial compounds. Antibacterial activity was measured by determining MIC and MBC values of various extracts against E. coli and P. aeruginosa. Sub-inhibitory concentrations of leaf and root methanol and water extracts were tested dose-dependently for effects on quorum-sensing-regulated virulence factors (pyocyanin, protease, elastase, hemolysis), biofilm formation, swarming motility, and expression of virulence genes (lasI, lasR, rhlI, rhlR, sfa, hlyA, cnf1). Results: Fourteen antibacterial compounds were identified, with the leaf methanol extract showing the strongest activity (MIC: 12.5 mg/mL; MBC: 50 mg/mL). Sub-MIC levels of leaf and root extracts significantly reduced virulence factor production, biofilm formation, and swarming motility, while downregulating quorum-sensing virulence genes in both pathogens. Discussion: T. hemsleyanum extracts reduced virulence in E. coli and P. aeruginosa by interfering with quorum sensing rather than relying solely on bactericidal effects. This anti-virulence approach may reduce selective pressure for resistance. The leaf methanol extract showed the strongest activity, suggesting phenolic or flavonoid compounds as likely drivers. Conclusion: T. hemsleyanum shows potential as an antimicrobial agent by disrupting quorum sensing and reducing bacterial virulence, supporting its development as a natural therapeutic.