Estudo da atividade antibacteriana de Protium hebetatum D. C. Daly por fracionamento fitoquímico biomonitorado

Abstract

The emergence of new mechanisms of bacterial resistance to antimicrobial agents available in the market has spawned a race between pharmaceutical industries for the production of novel compounds that act by distinct mechanisms to those present in existing drugs. Plants are considered a major source of discovery of new antibiotics due to the large molecular diversity and complexity of the biosynthesized metabolites, which is higher than that derived from chemical synthesis processes. Protium hebetatum D. C. Daly (Burseraceae) is a tree found mainly in the North of Brazil, Peru and Venezuela in upland forests. Considering the urgency of the search for new drugs for the treatment of bacterial infections and recognized antimicrobial activity of various plant extracts, this work conducted a biomonitored phytochemical study of antibacterial activity of extracts and fractions obtained from the leaves and branches of the species P. hebetatum, in order to identify and / or isolate substances with antibacterial activity by determining their minimum inhibitory concentration. Screening of the antibacterial activity of hexane methanol and ethyl acetate extracts from leaves and branches diffusion method, where the methanol extract of the branches was active against Escherichia coli and Proteus vulgaris showing the zone of inhibition of 13 mm. The same was partitioned with hexane, dichloromethane, ethyl acetate, generating respective samples were again screened by the same method. The dichloromethane partition showed inhibition zone of 13 mm against Staphylococcus aureus and 11, 3 mm against Enterococcus faecalis. The dichloromethane partition was subjected to fractionation column chromatographic generating 10 fractions, which together with the methanol extract and partition, had its MIC determined by the broth microdilution method. The methanol extract showed MIC of 1 mg/mL against S. aureus, Pseudomonas aeruginosa and E. faecalis. The partition and F1, F2, F5 and F6 fractions showed MIC of 1 mg/mL against S. aureus. The partition dichloromethane showed a MIC of 0.5 mg/ml against E. faecalis. By the technique of preparative thin layer chromatography and the analyzes performed by gas chromatography coupled to mass spectrometer (GC-MS), the α and β-amyrin and stigmasterol compounds were isolated, and identified the scopoletin, which are among the substances responsible for the activity antibacterial P. hebetatum. However, the results indicate that, in general, the methanol extract of the branches, containing the mixture of these substances, is more active than the samples obtained its fractionation, suggesting that this activity is due to a synergistic action of these compounds. Even employing the analysis by GC-MS, it was possible to identify isoeugenol, p- vinilguaiacol, metoxieugenol, coumarana, 5-hydroxy- scopoletin, 4,7dihydroxy-6-metoxicromam-2-one, piperonal, escoparona, o-guaiacol, spathulenol, syringol and antiarol, all first identified in this species. Thus, the results of this study suggest great pharmacological and technological potential for Protium hebetatum. Keywords: Protium hebetatum, antibacterial activity, Staphylococcus aureus, scopoletin, α-amyrin, β-amyrin and stigmasterol.