Atividade biológica de Eugenia uniflora L. (pitanga) e Psidium cattleianum S. (araçá) frente as bactérias Klebsiella pneumoniae e Acinetobacter baumannii

Abstract

Pneumonia is a pulmonary infection that characteristically involves the alveolar space and can be caused by Klebsiella pneumoniae and Acinetobacter baumannii. These bacteria, most of the time, are resistant to antibiotics, becoming one of the main challenges for public health worldwide. Due to this problem, the search for new antibiotics effective against these bacteria is essential. Medicinal plants are good alternatives, such as species from the Myrtaceae family, Eugenia uniflora L. and Psidium cattleianum S., which have several biological properties. The objective of this study was to extract, characterize physicochemically, evaluate the cytotoxicity in mammalian cells and determine the antioxidant, antibacterial and antibiofilm activity of essential oils (EO) and methanolic extracts (EM) of E. uniflora L. and P. cattleianum Sabine against standard strains and clinical isolates of K. pneumoniae and A. baumannii. In the chemical analysis of the EO of leaves of E. uniflora L. (OEE) and P. cattleianum S. (OEP) terpenoid compounds were found, the major constituents being benzofuran (24.38%) for OEE and α-pinene (24 .25%) for the OEP. Both EO tested showed a low antioxidant effect on DPPH (2,2, diphenyl-2-picrylhydrohydrazyl). As for the microbiological analyses, the OE that presented the best result was the OEP against A. baumannii, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 13.5 mg.mL-1. While for K. pneumoniae, the most active EO was the OEP, with a MIC of 121.4 mg.mL-1, showing no bactericidal effect. When the chemical composition of the EM of E. uniflora L. (EME) and P. cattleianum S. (PME) was analyzed, it was possible to identify phenolic acids. The PME showed the highest antioxidant activity at all concentrations tested (1 mg.mL-1; 0.5 mg.mL-1; 0.25 mg.mL-1 and 0.125 mg.mL-1). In the antibacterial activity, EME was the most active, as it presented the lowest MIC values for the standard strain of A. baumannii (9.2 µg.mL-1), while 50% of the isolates presented the same MIC concentration (9. 2 µg.mL-1), of which 33% showed a bactericidal effect. PME showed a percentage of biofilm inhibition of 88% and EME of 58.5% against the standard strain, while both extracts showed 88% of biofilm inhibition against the evaluated clinical isolate. Regarding the destructive effect of the preformed biofilm, the EME and PME did not show a percentage of inhibition against the standard strain of A. baumannii. In contrast to the multidrug-resistant isolate, EME destroyed 34% of the preformed biofilm and PME 42%. EME and PME took from 10 minutes to 6 hours to kill the standard strain and multidrug-resistant isolate of A. baumannii. Therefore, the results presented here are promising and demonstrate the biological activity of EO and EM E. uniflora L. and P. cattleianum Sabine for use in the development of new antimicrobials for the treatment of diseases caused by K. pneumoniae and A. baumannii.