Melão-de-são-caetano do Nordeste do Brasil (Momordica charantia l.): estudo farmacognóstico e microbiológico integrado ao estudo químico

Abstract

Momordica charanthia L., Curcubitaceae, is a plant used as food and in traditional medicine. The plant is included in the official list of Brazilian medicinal plants of interest to the Unified Health System. The objective of the present work is to carry out the pharmacognostic evaluation of Momordica charanthia of the macrocarp and microcarp varieties, and microbiological studies and modulator in the action of antimicrobials, with extracts and fractions of M. charanthia microcarpa variety ―melão-de-são-caetano‖ from Northeastern Brazil, including the chemical characterization of the active extracts by UPLC-QToF-ESI-MS. For pharmacognostic evaluation, fresh leaves of M. charantia L., of the microcarpa and macrocarpa varieties were used. Antimicrobial activity was evaluated with hydroalcoholic (EF) and acetone (FA) extracts from leaves, fruits (FrE; FrA) and seeds (SE; SA) of M. charantia microcarpa from northeastern Brazil, using the microdilution technique, in selected clinical bacterial and fungal strains. The extracts with significant antimicrobial activity were submitted to phytochemical profile evaluation using UPLC-QToF-ESI-MS. In addition, the most active extract was partitioned with solvents of increasing polarity, and the antimicrobial and synergistic effect, associated with conventional antibiotics by the Checkerboard technique, was evaluated again, against the microorganisms that showed greater sensitivity. The macromorphological and micromorphological results, respectively, demonstrated that the leaves of the macrocarpa variety are larger and the trichomes less frequent. The phytochemical approach of the two varieties has in common alkaloids, steroids, triterpenoids, flavonoids, saponins, phenolic compounds, condensed tannins and flavonoids. Momordicin II (C36H58O9) was isolated and identified, in the microcarpa variety, by NMR1H and NMR13C and 2D, a structure similar to that found in the variety of Asian origin. Leaf extracts showed a potent antibacterial effect against strains of Staphylococcus aureus and Staphylococcus epidermidis and weak antifungal activity against Candida albicans. Two fractions of the acetone extract showed an important synergistic effect, compared to all the antimicrobials tested except for vancomycin. Fourteen compounds were identified in the hydroalcoholic extract, while 12 were found in the acetone extract, among them kaempferol, quercertin and 7 cucurbitan type triterpenoids. Potential antibacterial activity has been demonstrated, particularly against microorganisms of clinical importance and resistant strains, in addition to having a synergistic activity when associated with antibiotics, against multi-resistant bacteria such as ORSA strains and in associations with antifungals against C. albicans, reducing their MIC up to sixteen times, which is important in inhibiting the development of bacterial resistance and in decreasing the adverse effects of these antimicrobials, especially aminoglycosides and fluoroquinolones. The phytochemical profile by UPLC-MS, showed important pharmacologically active metabolites, in the Brazilian variety, and is reported here for the first time. Further biological and pharmacological studies are needed to support the medicinal uses of this important plant. The Brazilian variety of M. Charantia can be a potential therapeutic agent in the treatment of clinically important infections.