Etude des équilibres de complexation par des cyclodextrines

Abstract

Local anesthetics (LAs) are agents that reversibly block nerve conduction. These are aminoamides or aminoesters. This work reports a combined experimental and theoretical study on the complexation reaction of the three local anesthetics, ProcHCl, TetracHCl and LidoHCl by a β-CD complexing agent. Characterization by UV-Vis, fluorescence (emission spectroscopy) and (1H) NMR spectroscopy shows that β-CD has the ability to encapsulate tois (ALs). We have reported the solvent effect by examining three dipole moments (ALs) namely in various mixtures of solvents. The absorption maxima of these (ALs) depend on the polarity of the solvent. The two transitions π-π* and n -π* which respectively indicate a bathochromic and hypsochromic shift are observed during the increase in the polarity of the solvents for the local andesites studied. Examination of the association constants by the polaremitric technique shows that the β-CD/ProcHCl and β-CD/TetracHCl complexes are more stable than βCD/LidoHCl. Quantum chemical calculations were carried out to study the complexation of Lidocaine hydrochloride with beta cyclodextrin (β-CD) in the gas phase to justify the formation of the complex. The analysis of the thermodynamic quantities shows that the formation of this complex is thermodynamically preferable and that its geometry is regular, on the other hand the analysis of the orbits (NBO) shows that the Van der Waals forces are responsible for the stability of this complex. Overall, the results of this study deepen our knowledge of molecular encapsulation systems using DCs, helping to expand the use of local anesthetics in complexed form in pharmaceutical formulations.