Effect of Illicium verum extract upon Quorum quenching mediated bacterial attenuation

Aim: The study aimed to evaluate the quorum-quenching (QQ) and anti-virulence potential of Illicium verum aqueous fruit extract against quorum-sensing (QS) regulated phenotypes of Chromobacterium violaceum MCC 2290 and Pseudomonas aeruginosa JB9, and to optimize key variables influencing QQ activity using a Box–Behnken response surface design. Method: A hot aqueous extract of I. verum fruits was prepared and subjected to phytochemical screening and activityguided fractionation. At doses ranging from 100-300 µg/mL, the phenotypic effects of QS inhibition were examined by suppressing violacein in C. violaceum MCC 2290, inhibiting pyoverdine pigment, and reducing biofilm formation in P. aeruginosa JB9. The cumulative impacts of three independent variables—bacterial density, extract concentration, and injection frequency—on quorum-quenching efficacy were evaluated using the Box–Behnken Response Surface Methodology (RSM). The active fraction was further characterized using GC–MS to identify the major bioactive compound. Result: I. verum extract exhibited strong concentration-dependent quorum-quenching activity, producing marked reductions in violacein production, pyoverdine synthesis, and biofilm formation without affecting bacterial growth. Maximum inhibition (84.38%) was observed at 300 µg/mL. The RSM model showed that all three factors significantly influenced QS inhibition, with extract concentration exerting the strongest effect, followed by bacterial density and dosing frequency. The quadratic model demonstrated excellent fit (p < 0.0001), confirming predictive reliability. GC– MS analysis identified the major active constituent as 1,2-Benzenedicarboxylic acid, dioctyl ester. Conclusion: Illicium verum aqueous extract possesses potent quorum-quenching and anti-virulence activity against key QS-regulated phenotypes of C. violaceum MCC 2290 and P. aeruginosa JB9. Optimization through Box–Behnken design highlights the importance of extract concentration and dosing strategy in maximizing QQ efficacy. The findings support the potential of I. verum as a promising non-bactericidal anti-virulence agent