The ban on the use of antibiotics in the feed of farm animals has promoted an active search for new substances with similar properties. Particular attention of researchers has been devoted to the search for these substances among medicinal plants. The effect of substances of vegetable origin, such as coumarin and coniferyl alcohol which both form part of oak bark, on the activity of acyl homoserine lactone (AHL) molecules has been investigated. Reporter luminescent test systems were used to

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... tify the stress effects using bioluminescent analysis. It was found that the absorption spectrum of coumarin is characterised by the presence of four peaks at 205, 215, 275, 310 nm. The interaction with coniferyl alcohol was characterised by a shift in the absorption maxima (250 and 265 nm). The introduction of a molecule of AHL into the system led to the disappearance of the peak at 250 nm and a significant decrease in the absorption at 265 nm. The formation of a complex of ruminal fluid and coumarin led to a decrease in the expression efficiency of the sensory promoter luxI to a level of 476626 RLU using the same concentration of GSL (homoserine lactone). The combination of ruminal fluid and coniferyl alcohol led to a decrease in the quantum yield of the E. coli strain to the level of 345896 RLU following the use of GSL at a concentration of 10 -4 M. The use of natural plant components (synthetic analogues) enhances the level of inhibition of quorum sensing (QS) system activity by the inactivation of regulatory molecules.