The natural products have been used since the immemorial times. One of the very first use forms of these natural products was by the ingestion of herbs and leafs in the search for relief and cure for diseases. Considering the richness of the Brazilian botanical diversity, the medicinal plants are highlights for the country, having around 23% of the world’s species. The utilization of them, especially in industrial scale, is diverse, highlighting industries of food, personal hygiene, cosmetics and drugs. Having their potential explained, the medicinal plants are, mostly, a broad source of bioactive compounds to be explored, stimulating researches about their insulation and mechanisms. The present work has verified the antimicrobial effectiveness of the Quassia amara L., Solanum sciadostylis (Sendtn) Bohs and Artemisia anua ethanolic extract in em Escherichia coli ATCC 25922, Enterobacter aerogenes LMI-UNIFAL, Serratia marcescens LMI-UNIFAL, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 25922 and Salmonella typhimurium ATCC 14028 using the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC), through the microdiluition in 96 wells plaque. The inoculum was prepared in a concentration of 10-2UFC.mL-1, from 0,5 McFarland (108 UFC.mL-1). The extract concentrations varied from 19-5000 ug.mL-1. The tested extracts showed similar results in front of all the tested organisms, with a MIC result of 1250 µg.mL-1 and MBC result of 5000 µg.mL-1 , except with Serratia marcescens, where the extract of Solanum sciadostylis and Artemisia annua did not show MBC. However, the study confirms the antimicrobial potential of these extracts, highlighting Quassia amara L., which has presented efficientiveness front of all the tested organisms, justifying new studies for the discovering of preservatives for the food industry.