Resumo

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired infections in many countries. Treatment of patients infected with MRSA is very difficult because MRSA is resistant to many common antibiotics. This means that is urgently necessary to develop new antibacterial agents that are effective for the treatment of infectious diseases caused by MRSA. Currently, plants are considered as a promising source for new antimicrobial agents, based on the fact that they produce an array of secondary metabolites, many of which are known to possess antibacterial activity. Thus, the objective of this study was to investigate the antibacterial activity of Mauritia flexuosa L.f. (Arecaceae) extracts against both MRSA and methicillin-sensitive Staphylococcus aureus (MSSA). Methods: Crude ethanol extracts from fruits, leaves and stems were submitted to liquid-liquid partition to furnish four different soluble fractions: hexane, dichloromethane, ethyl acetate and aqueous. The fractions were subjected to antibacterial activity against a total of 20 clinical isolates (being 10 of MRSA and 10 of MSSA). The antimicrobial activity was evaluated in vitro by determination of the minimal inhibitory and minimal bactericidal concentration (MIC and MBC) and also by time-kill curve tests. Results: None of the fractions had any antibacterial activity against MSSA isolates (at least up to 1000 μg/ml). However, the dichloromethane fraction from leaves (DML) showed potent activity against MRSA isolates (MIC and MBC range from 31.25 to 62.5 μg/ml). In addition, the time-kill curves revealed strong bactericidal effect of DML (at MIC concentration) within 8 hrs. Chromatographic fractionation and purification of the DML yielded an active compound, which we called MF-27. This compound had the same properties than DML against MRSA, except that its MIC was slightly lower (15.12 μg/ml). Conclusion: The surprising selective action of the dichloromethane fraction from leaves of M. flexuosa and its active constituent MF-27 towards MRSA make them potential candidates for anti-MRSA drug development.