Triagem in vitro de produtos naturais e derivados sintéticos em busca de inibidores de urease

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Universidade Federal de Goiás


Helicobacter pylori is a bacteria living in the stomach and it’s associated with several diseases in the gastrointestinal system. The survival and replication of H. pylori is related to the enzymatic activity of urease, which allow the resistance of bacteria to gastric acidity. Antimicrobial drugs are used against H. pylori, but there are occurrence of antibiotic resistance. In the view of the need for new antibacterial agents, this study aimed to investigate new compounds, of natural and synthetic source against urease. In vitro screening of compounds and Natural Products (NPs) was performed using the spectrophotometric method by measuring the reaction product (indophenol blue) at λ = 600 nm. The enzyme kinetics study of urease (Canavalia gladiata) (UJB) was performed for assay standard and the Km, Vmax and Kcat data (4.25 ± 0.62 mmol/L, 44.34 ± 1.33 mmol/L/min and 2062.3 s-1, respectively) were found similar to literature. Among the 37 chalcones assessed, nine showed significant inhibition (1a, 1c, 1g, 1h, 2a, 2b, 2c, 2d and 2m) with inhibitory potency ranging between IC50 = 5.7 and 18.8 µmol/L. The inhibition mechanism was determined for the most potent compounds by in vitro and in silico assays, which chalcones 1h (Ki = 2.98 µmol/L), 2a (Ki = 6.19 µmol/L), 2c (Ki = 1.87 µmol/L), and 2m (Ki = 3.13 µmol/L) showed competitive behavior and 1c non-competitive (Ki = 17.3 µmol/L). Chalcones 2c and 2m revealed the best MIC values (250 and 128 µg/mL, respectively) anti-H. pylori in vitro. Among NPs evaluated, five compounds from the fungus Fusarium proliferatum (5a-5e) were also inhibitors of UJB, which compounds 5a and 5b showed lower IC50 values with competitive behavior on urease (Ki of 0.55 and 1.1 µmol/L). Crystals obtained from the active extract of Pholiota nameko mushroom were analysed by 1D and 2D NMR experiments, and the compound was characterized as mannitol, which showed an IC50 value of 35.5 µmol/L on UJB. The inhibitory enzymatic activity by mannitol could be a clue for the gastroprotective action and anti-H. pylori potential found in previous work. By in silico screening, the pharmacokinetic properties of all compounds were investigated using Lipinski's Rule of Five (RO5) as the main parameter. In addition to bioavailability study of these compounds, it was possible to use the obtained results to understand better the chalcones behavior (2c and 2m) revealed on H. pylori in vitro assay. By using in vitro and in silico tests it was possible to find new and promising UJB inhibitors.



Urease, Helicobacter pylori, Inibidores, Urease, Helicobacter pylori, Inhibitors


ROSA, T. F. Triagem in vitro de produtos naturais e derivados sintéticos em busca de inibidores de urease. 2020. 113 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Catalão, 2020.