Antimicrobial activities and preliminary phytochemical tests of crude extracts of important ethnopharmacological plants from Brazilian Cerrado

Screening of native plants with therapeutical effects constitutes a valuable way to enhance biological attributes of medicinal herbs and discover new drugs. Therefore, ethanol and methanol extracts from ten plants collected from Brazilian Cerrado were tested to inhibitory effects against Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) through disc diffusion. The crude extracts that showed antibacterial activities from Anacardium humile, Psidium guineense and Myracrodruon urundeuva, were tested on the standard strain S. aureus ATCC 25923. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined and the interactions between the plant extracts and the main groups of secondary compounds present were investigated. The MICs of P. guineense, M. urundeuva and A. humile were all 4.1 mg/L for S. aureus. P. guineense and A. humile extracts tested against P. aeruginosa were 8.2 mg/L, whereas the extract from M. urundeuva had a MIC of 4.1 mg/L for the same strain. In addition, the observed MBCs were equivalent to the corresponding MICs. There were synergistic interactions in combinations of these plant extracts and tannins and flavonoids were identified in phytochemical analyses. These metabolites may be related to the biological activities that were found, indicating possible candidates for the development of strategies for treatment of infections caused by bacteria tested. Key words: Crude plant extracts, biological activity, disc diffusion, traditionally use, popular medicine, Cerrado biome.