Atividade antibacteriana do óleo essencial de Ageratum conyzoides L. sobre cepas isoladas de Listeria monocytogenes in vitro

Abstract

Listeriosis, a serious disease caused by the bacterium Listeria monocytogenes, is characterized by severe infections in humans and ruminants, and is mainly acquired through ingestion of contaminated food. Faced with the growing challenge of the development of antimicrobial resistance (AMR), there is significant interest from the scientific community in exploring new natural antimicrobial molecules. In this context, plant essential oils, known for their therapeutic properties, emerge as potential antimicrobial agents, arousing interest in their alternative or complementary use to traditional antibiotics. Therefore, this study aimed to evaluate the antimicrobial activity, chemical composition and cytotoxicity of the essential oil of Ageratum conyzoides Linnaeus (Asteraceae). The aerial parts of the A. conyzoides plant (leaves and flowers) were subjected to hydrodistillation in a Clevenger apparatus coupled to a Quimis ultrathermostatic bath, extracting the essential oil (EO), isolated with a yield of 0.7%. The essential oil of A. conyzoides (EOAc) was subsequently analyzed, and its chemical composition determined by Gas Chromatography-Mass Spectrometry (GC-MS). The antimicrobial activity, evaluated against four strains of L. monocytogenes (L. monocytogenes ATCC 7644 and three strains of food origin), was determined by the microdilution method, and the cytotoxic effect of EO was analyzed against RAW 264.7 murine macrophages, using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) colorimetric assay. GC-MS analysis allowed the identification of six chemical components present in the essential oil of A. conyzoides (100% of the total chemical composition). Of the total volatile constituents identified, two constituents, Precocene I (79.85%) and 􀈕-Caryophyllene (13.55%), were identified as the majority compounds. The other components were Bornyl acetate (1.55%), 􀈖-‐lemene (β.88%), 􀈕-Sesquiphellandrene (1.γ7%) and 􀈕-Nerolidol (0.80%). Analysis of antibacterial activity revealed that the investigated OEAc exhibits moderate to strong antimicrobial property, with Minimum Inhibitory Concentration (MIC) values ranging from γ1.β5 to β50 μg/mL. It also showed significant cytotoxicity against RAW β64.7 cells (CC50: 35 μg/mL). Thus, given its antibacterial properties, A. conyzoides essential oil appears to be a promising new source of natural antimicrobials, which will help in the development of new alternatives for the treatment of Listeriosis and innovative strategies to combat antimicrobial resistance