Resumo

Introduction: The widespread use of antibiotics leads to antimicrobial resistance and it has been limiting the options for treatment of infections. In this way, new antibiotics are of great importance for public health. The leaves and stems of Lafoensia sp. (Lythraceae), specie of the Brazilian Cerrado, had been evaluated in a bioprospecting program and showed antimicrobial activity. The aim of this work is to isolate the bioactive compounds present in the extracts of this plant. Methodology: The dry powder of the plant (leaves and stems) was extracted by percolation using eluents of increasing polarity: hexane (HE), dichloromethane (DCM), ethyl acetate (EA) and methanol (ME). The antimicrobial assays were performed by diffusion disc method and the Minimum Inhibitory Concentration (MIC) was determined. The microorganisms used were Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Candida albicans (ATCC 18804) and Cryptococcus neoformans (ATCC 24067). Chloramphenicol and amphotericin B were used as positive controls and ethanol and dimethylsulfoxide were the negative controls. All assays were carried out in duplicate at two separate experiments. Phytochemical screening was performed in all extracts using TLC plates and spray reagents. Results and discussion: The leaves ME extract showed activity against both bacteria and fungi in the diffusion disc test. The MIC value of this extract against the bacteria was of 500 μg/mL. Flavonoids and hydrolysable tannins were detected in this extract. The leaves EA extract (with terpenes, flavonoids and condensed tannins) also showed activity against both bacteria with MIC value of 125 μg/mL. From the stems of Lafoensia sp., the ME extract (with flavonoids and hydrolysable tannins) was active against both bacteria in the diffusion disc test and its MIC value was of 1000 μg/mL. Positive and negative controls were considered satisfactory. Conclusions: The more polar extracts of Lafoensia sp. were active against Gram-positive and Gram-negative bacteria and only the ME extract from the leaves showed activity against the tested fungi. The active extracts will be fractionated by chromatographic methods for isolation and identification of the active substance. Acknowledgements: FUNED and FAPEMIG for the financial support.