Etude des réactions de complexation mettant en jeu des cyclodextrines et des biomolécules

Abstract

This work reports a combined experimental and computational study on the complexation reaction of procaine hydrochlorate by three complexing agents: α-CD, -CD and HP--CD. Characterization by UV-Vis spectroscopy, fluorescence and one-dimensional and two-dimensional nuclear magnetic resonance shows that -CD and HP--CD have the ability to encapsulate procaine hydrochloride, while no effect on the spectral informations of this drug has only been recorded in the presence of α-CD. Examination of association constants indicates that the ProcHCl/-CD complex is more stable compared to ProcHCl/HP--CD. Quantum-chemical calculations were performed to study the complexation of procaine hydrochloride with beta cyclodextrin (β-CD) in the gas phase and in water. The inclusion process was optimized by the semi empirical method PM3 and the obtained complex structure was further refined by ONIOM method. Given the energy profile, the configuration of the complex formed indicates that the benzene ring is completely included in the cavity of the β-CD. The thermodynamic parameters analysis has shown that the procaine/β-CD complexation is enthalpically favorable, and the complex is well structured. Natural bond orbital (NBO) analysis indicates that the procaine/β-CD complex is mainly stabilized by Van der Waals forces.