Tesis
Avaliação da citotoxicidade e da atividade antimicrobiana e antioxidante do extrato hidroetanólico de leonotis nepetaefolia (l) r. Br.
Fecha
2013-05-23Registro en:
OLIVEIRA, Darley Maria. Avaliação da citotoxicidade e da atividade antimicrobiana e antioxidante do extrato hidroetanólico de leonotis nepetaefolia (l) r. Br. 2013. 96 f. Dissertação (Mestrado em Ciências da Saúde) - Universidade Federal de Mato Grosso, Faculdade de Medicina, Cuiabá, 2013.
Autor
Martins, Domingos Tabajara de Oliveira
http://lattes.cnpq.br/3794477872946546
Martins, Domingos Tabajara de Oliveira
109.726.923-04
http://lattes.cnpq.br/3794477872946546
Slhessarenko, Renata Dezengrini
006.990.439-13
http://lattes.cnpq.br/3790088995387532
109.726.923-04
Cruz, Alexandre Bella
480.657.909-25
http://lattes.cnpq.br/1596661935560930
Lopes, Lousa
879.675.298-04
http://lattes.cnpq.br/8843725522665416
Institución
Resumen
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