Quorum Quenching Potential of the Indigenous Kalimantan Fern Stenochlaena palustris Against Pseudomonas aeruginosa.

Background and Objective: Plant-derived compounds that disrupt bacterial quorum sensing (QS) provide alternatives to combat antibiotic resistance. This quorum quenching (QQ) strategy reduces virulence without inhibiting growth, thus minimizing resistance. Kelakai (Stenochlaena palustris (Burm.) Bedd.), an endemic Kalimantan plant traditionally used by the Dayak people, was evaluated for QQ activity against Pseudomonas aeruginosa. Materials and Methods: Ethanolic extract of S. palustris leaves was prepared by maceration with 96% ethanol. The extract was tested for inhibition of P. aeruginosa motility, pyocyanin production and LasA activity. Antibiofilm effects were assessed using the microtiter plate method, EPS quantified, chemical profiling performed by Liquid Chromatography-High-Resolution Mass Spectrometry (LC-HRMS) and acute toxicity evaluated in Rasbora lateristriata embryos. The results from three independent trials were analyzed in SPSS using one-way ANOVA followed by Dunn's test, with significance set at p<0.05. Results: At 0.25 mg/mL, the extract inhibited swarming and twitching by 58.04±0.46% and 64.98±0.25%, reduced LasA activity to 58.27±0.70% and reduced pyocyanin to 49.96±1.15%. Although antibacterial activity was weak, at a concentration of 0.25 mg/mL the extract caused 52.47±0.58% inhibition of P. aeruginosa biofilm formation and P. aeruginosa EPS was reduced to 67.40±0.54% of the untreated control. At a concentration of 1 mg/mL, pre-formed biofilm was eradicated as much as 58.52±0.23%. The LC-HRMS identified (-)-Strychnine, D-(+)-Pipecolinic acid and Ethyl oleate as major constituents. Toxicity testing revealed developmental toxicity in embryos at 0.06 mg/mL. Conclusion: Stenochlaena palustris ethanol extract showed strong QQ activity against P. aeruginosa, underscoring its potential as a natural anti-infective. Further isolation of active compounds with reduced toxicity is required for therapeutic development.