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Foodborne diseases still represent a public health problem worldwide. The resistance of microrganisms to various antibiotics has been stimulating research aimed at the discovery of new substances with natural antimicrobial action. The objective of this study was to evaluate the potential use of plants commonly used in folk medicine as antimicrobials. The decocts were submitted to the analysis of antimicrobial activity for Listeria monocytogenes, Salmonella Enteritidis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa by the microdilution technique. Croton blanchetianus stem bark extract presented the best results, being effective on all microrganisms tested in concentrations of 0.5 to 19 mg / mL. For the extract of the bark of the Myracrodruon urundeuva stem only activity on E. coli was not verified. The stem bark extract of Croton nepetaefolius showed activity on S. aureus and S. Enteritidis and only inhibitory for L. monocytogenes. The leaf extract of Sideroxylon obtusifolium was not effective only on E. coli and P. aeruginosa. In view of this, the aqueous extracts of these plants appear as a new source of substances with antibacterial potential for application in the food industry.

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O Croton blanchetianus Baill, conhecido como marmeleiro, é rico em metabólitos secundários, como alcalóides e terpenos, que podem apresentar efeitos biológicos. Desta forma, este estudo teve como objetivo avaliar o potencial bioativo, antioxidante e antimicrobiano dos extratos aquosos resultantes do processo de extração do óleo essencial das folhas frescas e secas do C. blanchetianus. O óleo essencial foi extraído por hidrodestilação e posteriormente o extrato aquoso foi coletado e liofilizado, sendo submetido às análises. A determinação da Concentração Inibitória Mínima e Concentração Bactericida Mínima contra bactérias patogênicas de interesse em alimentos (Staphylococcus aureus, Listeria monocytogenes, Salmonella Enteritidis e Escherichia coli) foi realizada pelo método de microdiluição. O efeito dos extratos aquosos sobre as células bacterianas foi avaliado por imagens de microscopia eletrônica de transmissão. A avaliação da atividade antioxidante foi determinada pelo método ABTS e DPPH. O extrato aquoso das folhas frescas apresentou maiores teores de flavonoides e atividade antioxidante por ABTS em comparação com o extrato de folhas secas. Os compostos fenólicos, taninos e a atividade antioxidante pelo método DPPH não diferiram significativamente entre ambos os tipos de folhas. Ambos os extratos aquosos apresentaram atividade antimicrobiana apenas sobre as bactérias Gram-positivas (S. aureus e L. monocytogenes). Foram observadas alterações celulares em S. aureus e L. monocytogenes sob ação do extrato aquoso de folhas frescas e secas. Os resultados indicam a possibilidade de utilização do extrato aquoso das folhas secas de C. blanchetianus como aditivo bioativo e para melhoria da segurança de alimentos, no que diz respeito às bactérias Gram-positivas.

The plants popularly used in the treatment of various diseases, such as Myracrodruon urundeuva Allemão, have been investigated about the action on microorganisms, aiming the discovery and use of new natural additives. This research aimed to evaluate the in vitro antimicrobial activity of the aqueous extract of Myracrodruon urundeuva leaves and its fractions on pathogenic bacteria associated with foodborne diseases. The aqueous extract was obtained by decoction of the fresh leaves and fractionated by high-speed counter-current chromatography. The antimicrobial activity was performed using microdilution in a plate. The aqueous extract of “aroeira-do-sertão” leaves was effective against all tested microorganisms. Antimicrobial activity was verified for Staphylococcus aureus and Listeria monocytogenes (0.2 and 0.8 mg/mL, respectively) and for Salmonella Enteritidis, Pseudomonas aeruginosa, and Escherichia coli (6, 10 and 16 mg/mL respectively). Twenty-four secondary compounds were isolated, distributed in six fractions. The fractions showed antimicrobial activity on Gram-positive bacteria at low concentrations (0.011 to 0.095 mg/mL) and at higher concentrations (2.4 to 33 mg/mL), two fractions showed activity on Gram-negative bacteria. The union of the compounds in the extract was favorable for antimicrobial activity on all the studied bacteria, demonstrating that the susceptibility of the microorganisms to the extract varied according to the chemical compounds present.