First report: Tagetes erecta inhibits quorum-sensing in Pseudomonas aeruginosa

Introduction: Pseudomonas aeruginosa is an opportunistic pathogen that expresses multiple quorum sensing (QS)-regulated virulence factors, including pyocyanin, alginate, exoprotease, and elastase. Disruption of these QS-regulated pathways constitutes a promising antivirulence strategy, as it interferes with bacterial communication without exerting selective pressure for resistance. This study evaluates the effect of Tagetes erecta extract on the inhibition of QS-dependent virulence factors in three P. aeruginosa strains: Pa01, Pa14, and ATCC 27853. Method: The Tagetes erecta extract was analyzed at concentrations of 500, 750, and 1000 µg/mL. The effect of the extract on pyocyanin and elastase production was quantified by spectrophotometry. Results: The results showed that the T. erecta extract produced a strong inhibition of pyocyanin in all strains, with inhibition percentages exceeding 95% even at the lowest concentration. This suggests a potent and early effect, likely independent of dose. Elastase production, on the other hand, showed variable responses between strains, with reductions in Pa14 and ATCC 27853 compared to Pa01, although without a clearly consistent pattern. Conclusions: These findings indicate that the T. erecta extract may contain compounds capable of interfering with QS signaling, particularly in inhibiting phenazine pigments such as pyocyanin. Further studies are needed to isolate and characterize the active phytocompounds involved and evaluate their effects in more complex biological systems, highlighting the potential of Tagetes erecta as a new source of antiviral agents.