Medicinal plants have attracted increasing scientific interest due to the diversity of bioactive compounds reported across different species. They may represent complementary sources of bioactive compounds alongside conventional antimicrobials, which may pose risks to animal health and compromise treatment efficacy. Considering the importance of alternative compounds, we aimed to evaluate the antimicrobial activity in vitro of medicinal plants Stryphnodendron adstringens (Mart.) Coville, known as barbatimão, Baccharis crispa Spreng, known as carqueja and Azadirachta indica, known as neem. S. adstringens (Mart.) Coville and B. crispa Spreng were used as extract and obtained from plants collected in the municipality of Bambuí, state of Minas Gerais, Brazil. A. indica was evaluated as extract and oil, and the crushed leaves and oil were purchased from a commercial company. Antimicrobial activity was determined by the minimum bactericidal concentration (MBC) test-against Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis, Escherichia coli, and Salmonella spp., isolated from bovine mastitis. The bacteria were submitted to the MBC test at concentrations of 100, 50, 25, 12.5, 6.25, 3.12, 1.56, 0.78, 0.39, 0.19 and 0.09 mg/mL. The bacteria evaluated were sensitive to most plant extracts for at least one of the concentrations evaluated, except for Gram-negative bacteria, Escherichia coli, and Salmonella spp. There was no activity of B. crispa Spreng extract and A. indica against E. coli and neither of B. crispa Spreng extract against Salmonella spp. even at the highest concentration evaluated. S. adstringens (Mart.) Coville was considered the extract with the highest activity against the bacteria evaluated and S. uberis the most susceptible to antimicrobial action. The results indicate detectable antimicrobial activity of the evaluated extracts and oil, suggesting their potential relevance as complementary sources of bioactive compounds for further investigation, rather than as direct alternatives to conventional antibiotic therapies. Paper spray mass spectrometry (PS-MS) was employed as an exploratory phytochemical screening approach, and all metabolite assignments reported herein should be regarded as tentative or putative annotations under the analytical conditions used, consistent with MSI Level 3 confidence.
Nascimento et al. (Fri,) studied this question.
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