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

Pseudomonas aeruginosa is an opportunistic pathogen that expresses multiple virulence factors regulated by quorum sensing (QS), including pyocyanin, alginate, exoprotease and elastase. Disrupting these QS-regulated pathways is a promising anti-virulence strategy, as it interferes with bacterial communication without exerting selective pressure for resistance. In this study, the effect of Tagetes erecta extract on the inhibition of QS-dependent virulence factors was evaluated in three strains of P. aeruginosa: PaO1, Pa14, and ATCC 27853. The extract was tested at concentrations of 500, 750, and 1000 µg/mL, and its effect on pyocyanin and elastase production was quantified spectrophotometrically. The results showed that T. erecta extract produced strong inhibition of pyocyanin in all strains, with inhibition percentages greater than 95% even at the lowest concentration. This suggests a potent and early effect, likely independent of dose escalation. In contrast, elastase production showed more variable responses among strains, with apparent reductions in Pa14 and ATCC 27853 compared to PaO1, although without a clearly consistent pattern. These findings indicate that the extract of T. erecta may contain compounds capable of interfering with QS signaling, particularly in the inhibition of phenazine pigments such as pyocyanin. Further studies are needed to isolate and characterize the active phytocompounds involved, as well as to evaluate their effects in more complex biological systems. These findings highlight the potential of Tagetes erecta as a novel source of antivirulence agents, warranting further phytochemical characterization and in vivo studies.