Avaliação da citotoxicidade e da atividade antimicrobiana e antioxidante do extrato hidroetanólico de leonotis nepetaefolia (l) r. Br.

• Ano de defesa: 2013
• Autor(a) principal: Oliveira, Darley Maria
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Faculdade de Medicina (FM); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Ciências da Saúde
• Palavras-chave em Português: Leonotis nepetefolia; Antimicrobiano; Citotoxicidade; Antioxidante; CNPQ::CIENCIAS DA SAUDE::MEDICINA; Antimicrobial; Cytotoxicity; Antioxidant
• Link de acesso: http://ri.ufmt.br/handle/1/1590

Leonotis nepetifolia (L.) R. Br (Lamiaceae), popularly known as “cordão-de- frade”, is a sub-spontaneous shrub. The tea from the whole plant is used in the treatment of infections, inflammations, wounds and stomach ulcers. The present study evaluates the potential antimicrobial, antioxidant and cytotoxicity of the hydroethanolic extract of L. nepetifolia (HELn). The whole plant was washed, dried, powdered and the resulting powder was macerated in hydroethanolic solution (1:5, w/v), filtered, concentrated in rotaryevaporator and the residual solvent was eliminated in hotair oven, thus obtaining HELn. Chinese hamster ovary cells (CHO-K1) were used for cytotoxicity studies by Alamar blue method. To evaluate the antimicrobial activity against a panel of Gram-positive and Gram-negative bacteria and yeasts and filamentos fungi, disk diffusion test and broth microdilution were used. Drugs with inhibition zones of ≥ 10 mm and minimal inhibitory concentration (MIC) <100 µg/mL were considered very active. To characterize the nature of the antibacterial activity, antibiosis mechanism study was conducted, evaluating the growth of sensitive bacteria to concentrations of HELn ≥ MIC within 24 h. To assess the antibacterial mode of action of HELn on the permeability of the outer membrane, synergism between the extract (0.5 MIC) and hydrophobic antibiotics- erythromycin and rifampicin (0.68 to 20 µg/mL), was determined in Shigella flexneri. However, the mode of action of of HELn on the cytoplasmic membrane was evaluated by measuring the potassium efflux (2 MIC) and nucleotides leakages (1 MIC), using electrolytes analyzer and spectrophotometer respectively, in strains of E. faecalis and S. flexneri. The antioxidant activity was determined in vitro by DPPH, NO and H2O2 radical scavenging assays. The IC50 of HELn in the cytotoxicity assay was greater than 200 µg/mL. HELn demostrated a good spectrum of antibacterial activity in broth microdilution assay against S. flexneri, S. aureus and E. faecalis (MIC= 6.25 µg/mL), H. pylori (MIC= 25 µg/mL) and S. pyogenes (MIC= 50 µg/mL). With chloramphenicol, the MIC varied between 3.12 µg/mL (S. flexneri ) and 100 µg/mL (P. aeruginosa). In the disk diffusion assay, HELn was inactive, while chloramphenicol produced inhibition halos of 30 mm against all strains tested. HELn presented a bacteriostatic action against the sensitive bacterial strains. In the presence of HELn, S. flexneri became more sensitive to the probe antibiotics at MIC of erythromycin (1 µg/mL) and below the MIC of rifampicin (5 µg/mL). HELn caused an intense damage to the cytoplasmic membrane, reaching a maximum K+ efflux of 11.7 ± 0.6 ppm and 12.87 ± 0.3 ppm, and of the nucleotide 22% (6th hour) and 46% (12th time ) in E. faecalis and S. flexneri, respectively. EHLn had no effect on fungal growth, unlike amphotericin B, which was active in both models of disk diffusion and broth microdilution, attaining maxima activity against yeasts (35 mm) and filamentous fungi (3.12 µg/mL). HELn demonstrated weak antioxidant activity with IC50 (µg/mL) of 128.94 ± 8.7, 190.93 ± 0.01 and > 250 for DPPH, NO and H2O2 radical scavenging assays respectively. The results indicate that HELn has low cytotoxicity and antioxidant activity and potent antibacterial activity, especially against Gram-positive bacteria,. It is bacteriostatic in nature, possibly acting at the level of the cell wall and cytoplasmic membrane thus supporting its popular use in infectious processes. In addition, the presence of phenols, flavonoides, carotenoids, fatty acids and esteroids, described in the literature to posses antioxidant and antimicrobial, were detected in the composition of HELn