Isolamento de metabólitos secundários de Mesosphaerum pectinatum bioguiado por ensaios antimicrobianos frente a cepas de Staphylococcus aureus

Abstract

INTRODUCTION: Mesosphaerum pectinatum (Lamiaceae), popularly known as "sambacaitá" is extensively used by the population for the treatment of inflammation, bacterial infections and pain, in the form of decoction and infusion. Although some M. pectinatum substances have already been evaluated biologically, there is still much to explore. An alternative to obtain pure and biologically active compounds from plant extracts is through the bioguided study, whereas the fractionation is performed, the fractions and subfractions obtained are submitted to tests discovering where the biological activity is concentrated. OBJETIVE: To isolate and identify compounds, present in leaves and/or flowers of M. pectinatum, that present antimicrobial activity. METHODS: Extracts and fractions of M. pectinatum were tested on strains of Staphylococcus aureus using the agar diffusion method. The extracts from the most active part of the plant were fractionated by liquid-liquid partition and classical liquid chromatography (CLC). The most bioactive fractions were analyzed and their constituents isolated by HPLC. For the structural elucidation of the isolated substances, analyzes by 1H and 13C Nuclear Magnetic Resonance (NMR) were performed. RESULTS: The hexane fraction (more active) from the leaves of M. pectinatum was refracted by CLC generating seven new fractions. These were evaluated for antimicrobial activity and the most active subfraction was submitted to a further CLC fractionation. Subsequently, its subfractions were submitted to HPLC analysis for further isolation and evaluation of the antimicrobial activity of the isolated substances. After analysis by 1H NMR and 13C NMR of the isolated substances, the triterpenes: micromeric acid - isolated in this species for the first time were identified; oleanolic and ursolic acid. After the evaluation of the antimicrobial activity, a high inhibition of microbial growth (MIC 100 g/mL) was observed for ursolic acid, while the other substances had no inhibitory effect at 500 g/mL. CONCLUSION: These results contribute to explain the popular use of this species as a therapeutic agent, however, further studies (in vitro and in vivo) should be performed in order to evaluate its effectiveness and toxicity.