Análise estrutural de ciclodextrinas: um estudo comparativo entre métodos teóricos clássicos e quânticos Structural analysis of cyclodextrins: a comparative study of classical and quantum mechanical methods

<abstract language="eng">In the present work, we analyzed the accuracy of distinct theoretical methods to reproduce the solid state structures of cyclodextrins. The a, b and g-cyclodextrins (CD) were considered and also their hydrates with included water molecules: a-CD.2H2O, b-CD.10H2O and g-CD.12H2O. The geometries were fully optimized using Molecular Mechanics (MM2), semiempirical (AM1 and PM3) and ab initio (HF/3-21G) methods and quantitatively compared with experimental data from X ray diffraction. The results obtained from the classical MM2 method were in best agreement with the experiment. The semiempirical and ab initio structures were also in satisfactory accordance with the experimental data. In general, the PM3 method was found to be more suitable than the AM1 to describe the CD geometries, mainly when the intramolecular hydrogen bonds are considered

Computational investigation on the host–guest inclusion process of norfloxacin into β-cyclodextrin

A theoretical 1H NMR spectroscopy and thermodynamic analysis of the host–guest inclusion process involving the norfloxacin (NFX) into β-cyclodextrin (β-CD) was carried out. DFT structure and stabilization energies were obtained in both gas and aqueous phases. We could establish that the complex formation is enthalpy driven, and the hydrogen bonds established between NFX and β-CD play a major role in the complex stabilization. Besides, a theoretical 1H NMR analysis has shown to be a supplementary proceeding to predict appropriately the inclusion mode of norfloxacin molecule into the β-CD. In this work, a theoretical study of the NFX@β-CD complex is reported for the first time, seeking a deep understanding of topology and thermodynamics of the inclusion complex formation

Theoretical investigation on the molecular inclusion process of prilocaine into p-sulfonic acid calix[6]arene

The present letter reports, for the first time, results from a theoretical analysis of the inclusion process involving the prilocaine into the p-sulfonic acid calix[6]arene. Structure and stabilization energies were calculated, in both gas and aqueous phases, using a sequential methodology based on semiempirical and Density Functional Theory (DFT) calculations. From the results, a qualitative structure property relationship could be established with some main structural features being relevant for inclusion complex stabilization: (i) the hydrogen bonds established between guest and host molecules, (ii) the dispersion effect and (iii) the inclusion mode of guest molecule into the host cavity

Theoretical and experimental study of inclusion complexes formed by isoniazid and modified β-Cyclodextrins: 1H NMR structural determination and antibacterial activity evaluation

Me-β-cyclodextrin (Me-βCD) and HP-β-cyclodextrin (HP-βCD) inclusion complexes with isoniazid (INH) were prepared with the aim of modulating the physicochemical and biopharmaceutical properties of the guest molecule, a well-known antibuberculosis drug. The architectures of the complexes were initially proposed according to NMR data Job plot and ROESY followed by density functional theory (DFT) calculations of (1)H NMR spectra using the PBE1PBE functional and 6-31G(d,p) basis set, including the water solvent effect with the polarizable continuum model (PCM), for various inclusion modes, providing support for the experimental proposal. An analysis of the (1)H NMR chemical shift values for the isoniazid (H6',8' and H5',9') and cyclodextrins (H3,5) C(1)H hydrogens, which are known to be very adequately described by the DFT methodology, revealed them to be extremely useful, promptly confirming the inclusion complex formation. An included mode which describes Me-βCD partially enclosing the hydrazide group of the INH is predicted as the most favorable supramolecular structure that can be used to explain the physicochemical properties of the encapsulated drug. Antibacterial activity was also evaluated, and the results indicated the inclusion complexes are a potential strategy for tuberculosis treatment