Title: Evaluation of antimicrobial activity of the crude extract of three Bauhinia species from the Brazilian Amazon

Abstract The Bauhinia ungulata, Bauhinia variegata, and Bauhinia purpurea are commonly used in folk medicine. However, few studies have investigated its antimicrobial potential. This study evaluated the in vitro antibacterial effect of crude extracts from leaves of B. ungulata, B. variegata and B. purpurea, in addition to identifying the class of constituents. The evaluation of antimicrobial activity was determined using the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) methods against American Type Collection Culture (ATCC) strains of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes and Klebsiella pneumoniae. All crude extracts showed similar phytochemical analysis with saponins and tannins and bactericidal activity against all the bacterial strains. The extract of B. variegata stood out with a MIC of 3.6 µg/mL against P. aeruginosa. From this perspective, the extracts of Bauhinia spp. showed promising microbial activity and should be further investigated for the development of antibacterial agents of natural origin.