RESUMO
The aim of the present work was to modify the exuded gum of Sterculia striata tree by an amination reaction. The viscosity and zero potential of the chicha gum varied as a function of pH. The modification was confirmed by X-ray diffraction (XRD), infrared spectroscopy (FTIR), size exclusion chromatography (SEC), zeta potential, thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). Furthermore, the chemical modification changed the molar mass and surface charge of the chicha gum. In addition, the gums were used in tests for ex vivo mucoadhesion strength, antibacterial activity against the standard strain of Staphylococcus aureus (ATCC 25923), inhibitory activity of α-glucosidase, antioxidant capacity, and viability of Caco-2 cells. Through these tests, it was found that amination caused an increase in the mucoadhesive and inhibitory activity of chicha gum against the bacterium Staphylococcus aureus. In addition, the gums (pure and modified) showed antioxidant capacity and an inhibitory effect against the α-glucosidase enzyme and did not show cytotoxic potential.
Assuntos
Antioxidantes , alfa-Glucosidases , Humanos , Antioxidantes/farmacologia , Células CACO-2 , Antibacterianos/farmacologia , Antibacterianos/química , Difração de Raios X , Gomas Vegetais/farmacologia , Gomas Vegetais/química , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
Proteins are essential macromolecules for the maintenance of living systems. Many of them perform their function by interacting with other molecules in regions called binding sites. The identification and characterization of these regions are of fundamental importance to determine protein function, being a fundamental step in processes such as drug design and discovery. However, identifying such binding regions is not trivial due to the drawbacks of experimental methods, which are costly and time-consuming. Here we propose GRaSP-web, a web server that uses GRaSP (Graph-based Residue neighborhood Strategy to Predict binding sites), a residue-centric method based on graphs that uses machine learning to predict putative ligand binding site residues. The method outperformed 6 state-of-the-art residue-centric methods (MCC of 0.61). Also, GRaSP-web is scalable as it takes 10-20 seconds to predict binding sites for a protein complex (the state-of-the-art residue-centric method takes 2-5h on the average). It proved to be consistent in predicting binding sites for bound/unbound structures (MCC 0.61 for both) and for a large dataset of multi-chain proteins (4500 entries, MCC 0.61). GRaSPWeb is freely available at https://grasp.ufv.br.
Assuntos
Aprendizado de Máquina , Proteínas , Proteínas/química , Sítios de Ligação , Ligantes , Domínios Proteicos , Ligação ProteicaRESUMO
Natural polysaccharides have been investigated as vehicles for oral insulin administration. Because of their non-toxic, renewable, low cost and readily available properties, gums find multiple applications in the pharmaceutical industry. This work aimed to develop a Sterculia striata gum-based formulation associated with additional biopolymers (dextran sulfate, chitosan, and albumin), a crosslinking agent (calcium chloride) and stabilizing agents (polyethylene glycol and poloxamer 188), to increase the oral bioavailability of proteins. Insulin was used as a model drug and the methods used to prepare the formulation were based on ionotropic pregelation followed by electrolytic complexation of oppositely charged biopolymers under controlled pH conditions. The developed formulation was characterized to validate its efficacy, by the determination of its average particle size (622 nm), the insulin encapsulation efficiency (70%), stability in storage for 30 days, and the in vitro mucoadhesion strength (92.46 mN). Additionally, the developed formulation preserved about 64% of initial insulin dose in a simulated gastric medium. This study proposed, for the first time, a Sterculia striata gum-based insulin delivery system with potential for the oral administration of protein drugs, being considered a valid alternative for efficient delivery of those drugs.
Assuntos
Goma de Karaya/química , Preparações Farmacêuticas/química , Proteínas/química , Sterculia/química , Administração Oral , Disponibilidade Biológica , Biopolímeros/química , Cloreto de Cálcio/química , Portadores de Fármacos/química , Sistemas de Liberação de Medicamentos/métodos , Liberação Controlada de Fármacos , Insulina/química , Tamanho da Partícula , Poloxâmero/química , Polietilenoglicóis/químicaRESUMO
Molecular dynamics simulations and binding free energy calculations were employed to examine the interaction between E-selectin and six structurally related oligosaccharides including the physiological ligand sialyl Lewis x. Molecular dynamics simulations revealed that sialyl Lewis x and its mimics share a common binding region and similar interactions with E-selectin involving the formation of hydrogen bonds with Glu80, Asn82, Asn83, Arg97, Asn105, Asp106, and Glu107 residues and electrostatic contacts with Ca2+ and the positively charged Lys111 and Lys 113 residues. Regarding binding free energy calculations, the performance of the rigorous but computationally expensive pathway methods TI, BAR, and MBAR was compared to the less rigorous but faster end-point methods MM/PBSA and MM/GBSA aimed at identifying a suitable approach to deal with the very subtle binding free energy differences within the ligands under study. All methods succeeded in predicting increased binding affinities for sialyl Lewis x analogs compared to the native ligand with absolute errors <1 kcal/mol. The best correlation with experimental data was obtained by TI (r2 = 0.84), followed by MBAR (r2 = 0.80), BAR (r2 = 0.73), MM/PBSA (r2 = 0.73) and MM/GBSA (r2 = 0.47). These results provide valuable information to increase understanding about E-selectin-oligosaccharide interactions and conduct further research aimed at designing novel ligands targeting this protein.
Assuntos
Selectina E/química , Oligossacarídeos/química , Ligação de Hidrogênio , Simulação de Dinâmica Molecular , Antígeno Sialil Lewis X , Eletricidade EstáticaRESUMO
In the present study, we evaluated 457 patent applications filed for crystalline forms of nonprotein drugs during the period 1995-2005 in Brazil. Online searches were conducted using the Instituto Nacional da Propriedade Industrial patent database and the Derwent Innovations Index(®). It was found that no patent applications in this area were filed by Brazilian applicants. It was also noted that only 61% of patent applications included the characterization of three or more crystalline phase techniques. In most applications, no determination of purity was provided for chemical and/or crystalline phases. In a subset of patent applications, those for blockbuster drugs, we found that approximately 90% did not meet Instituto Nacional da Propriedade Industrial acceptance criteria nor the criteria developed in this study. These results reveal that appropriate and thorough characterization of the crystalline forms of drugs is, indeed, lacking in patent applications.