Atividade antibacteriana de Ageratum conyzoides L. sobre microrganismos patogênicos in vitro

Abstract

The increasing problem of microbial resistance has intensified the search for new therapeutic alternatives from medicinal plants. Ageratum conyzoides L., popularly known as mentrasto, is highlighted for its bioactive compounds with recognized antimicrobial properties. This study evaluated the antibacterial potential of the essential oil, crude extract, and fractions of A. conyzoides L. against pathogenic microorganisms of public health importance, correlating chemical composition with biological activity. The essential oil was obtained by hydrodistillation, while the crude extract was prepared with solvents and fractionated, including the ethyl acetate fraction. Chemical characterization was performed using gas chromatography– mass spectrometry (GC-MS), which enabled the identification of major and minor compounds. Antimicrobial activity was assessed by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), using reference bacterial strains and comparing results with standard antibiotics. Cytotoxicity of the extracts and oil was also evaluated on RAW 264.7 murine macrophages through the MTT assay. The crude extract and especially the ethyl acetate fraction exhibited significant antibacterial effects, with MIC values consistent with relevant antimicrobial activity. GC-MS analysis revealed terpenes and flavonoids among the main metabolites, which likely contribute to the observed effects. The essential oil demonstrated a favorable safety profile, showing no significant cytotoxicity even at high concentrations (up to 1000 μg/mL). In conclusion, A. conyzoides L. represents a promising natural source of antimicrobial biomolecules with low cytotoxicity. The ethyl acetate fraction stood out as the most active, making it a strong candidate for further studies aiming at compound isolation and development of phytotherapeuti