Atividade antimicrobiana e antioxidante de metabólitos bioativos e óleo essencial de plantas da caatinga: Myroxylon peruiferum L.f e Combretum leprosum

Abstract

The increase in microbial infections plus the resistance that these agents have developed to conventional antimicrobials has led to a search for effective therapeutic alternatives that offer better solutions for treatment. Species of the genus Combretum and Myroxylon demonstrate some biological activities such as antibacterial, antifungal and antibiofilm. Thus, the triterpene of C. leprosum 3β-6β-16β-trihydroxylup-20(29)-en (CLF1) and isoflavone 7-hydroxy-4',6-dimethoxy-isoflavone with the essential oil of M. peruiferum were used in the study with the objective of verifying the antimicrobial activity and antibiofilm. The Minimal Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (CFM) were determined by the broth microdilution method. Synergism was evaluated by the checkerboard method with the combination of triterpene with ampicillin and tetracycline. Biofilm formation was evaluated through the quantification of biomass by the crystal violet (CV) staining method and enumeration of viable cells, whereas the metabolic activity was analyzed by the XTT method. For the antioxidant activity, were realized the tests of 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferrous ion chelating (FIC), iron reduction (FRAP), inhibition of β-carotene oxidation (BCB). Bacteria and fungi species had their planktonic growth completely inhibited by triterpene and isoflavone at concentrations ranging from 2000 to 1.9μg/mL; for essential oil ranged from 5 to 1.25%. CLF1 showed synergistic effect with ampicillin for S. aureus ATCC 25923, S. aureus ATCC 700698, S. epidermidis ATCC 35984, S. epidermidis ATCC 12228 and with tetracylin for S. aureus ATCC 25923, S. aureus ATCC 700698 and S. epidermidis ATCC 35984, whereas for S. epidermidis ATCC 12228 presented antagonistic effect. In relation to antibiotic tests, CLF1 induced a reduction in biomass and viable cells (CFU) for all Gram-positive bacteria. For the XTT method, S. aureus strain ATCC 25923 and S. aureus ATCC 700698 had a greater metabolic reduction than S. epidermidis ATCC 12228 and S. epidermidis ATCC 35984. About antioxidant activities, treatments with essential oil and isoflavone resulted in antioxidant effects in all assays and concentrations performed, mainly in BCB with a 100% inhibition, proving to be more active than the positive control. Therefore, the results demonstrated that the secondary compounds and the essential oil used in this study can be considered as potential antimicrobial agents and antibiotics, suggesting the use of these molecules in the treatment of infections associated with different microorganisms.