Avaliação in vitro da atividade anti-Helicobacter pylori e potencial antioxidante de extratos e frações de Baccharis trimera (Less.) DC
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Data
2016-03-22
Autores
Nunes, Otalibio Castiglioni
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Universidade Federal do Espírito Santo
Resumo
One of the major risk factors for the development of ulcers and gastric cancer is the infection by Helicobacter pylori, in which there is a considerable oxidative stress. In Brazil, the plant Baccharis trimera (Less) DC, known as "Carqueja", is commonly used to treat gastrointestinal and liver disorders. Tannins, flavonoids, saponins, diterpene lactones, sesquiterpenes, phenolic compounds and volatile oils were identified in this specie. Thus, the goal of this study was to evaluate the antiHelicobacter pylori activity of the aqueous (AqE), ethanolic (EE), and hydroalcoholic (HE) extracts of B. trimera, as well as the aqueous (AqF), hexane (HxF), and acetonitrile / chloroform (ACF) fractions obtained from the HE. In addition, it aims to analyze the phytochemical composition and its effects on free radicals and biological oxidants. For all extracts and fractions, it was performed a phytochemical screening and the determination of the content of polyphenol, flavonoid and total tannins. The anti- Helicobacter pylori activity was evaluated by microdilution broth assay and urease inhibitory capacity. Bacterial morphology, after sample exposure, was evaluated by scanning electron microscope (SEM) using the extracts and fractions that reached the minimum inhibitory concentration (CIM90). Screening of antioxidant activity for all samples was determined by DPPH and ABTS radical scavenging activities. Assays using the oxidizing biological agents, hydrogen peroxide (H2O2), superoxide anion (O2 •- ), hypochlorous acid (HOCl), hydroxyl radical (HO• ), and nitric oxide (NO• ) were performed with HE and its fractions due the best results in the antiH. pylori and initial screening antioxidant assays, except for the HxF because of its poor performance in the antioxidant screening. The highest concentration of polyphenols was observed in the HE, flavonoids in the ACF, and tannins in the AqF. Anti-H pylori assay presented a CIM90 of 512 μg/mL for HE, and 1024 μg/mL for ACF, the latter being bactericidal. SEM showed morphological changes such as stretching and cell lysis in the samples tested, and may suggest some modifications in the wall, such as alterations in the peptidoglycan synthesis. In the enzyme urease inhibition assay, the most significant result was obtained by the ACF, which inhibited 36.24% in the highest concentration tested. The best result among the extracts in the initial antioxidant screening was achieved by the HE, which obtained the following EC50: DPPH, 17.40 ± 0.52 and ABTS, 9.99 ± 1.21. The best EC50 for the fractions were: DPPH, AqF, 27.41 ± 1.65, and ABTS, AqF, 10.80 ± 1.90. In the O2 •- scavenging activity, AqF showed EC50 of 5.85 ± 0.86 μg/mL. In the inhibition assay of HOCl, all samples tested were able to inhibit greater than 50%, except AqF. In the inhibition assay of HO• , NO• e H2O2, the results were better for ACF and its EC50 was 2.90 ± 0.48, 132.13 ± 7.38 e 66.70 ± 2.30 μg/mL, respectively. The analyzes indicate that B. trimera, in particular the HE and its fractions, AqF and ACF, may exhibit promising compounds for the prevention and treatment of diseases caused by H. pylori. These results were based on the relationship between the presence of phenolic compounds and the inhibition of oxidants, as well as changes in the bacterial membrane.
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Oxidative stress , Helicobacter pylori , Baccharis trimera , Estresse oxidativo , Compostos fenólicos , Ação antioxidante