Spectral analysis of inclusion complex formed by Omeprazole and 2- Hydroxypropyl β-cyclodextrin
The effects of inclusion of omeprazole in the cavity of hydroxypropyl β-cyclodextrin on the absorbance, fluorescence, twisted intermolecular charge transfer (TICT), lifetime of emission decay, association constants, proton shifts and ΔG in aqueous solution were investigated by adopting spectroscopic methods. OMP forms 1:1 inclusion complex at low concentrations of HP-β-CD and 1:2 inclusion complex at higher concentrations of the CD, which was confirmed by UV absorbance, emission, Job plot and 1H NMR studies. FTIR spectra also supported the formation of both types of inclusion complexes. The association constants and negative ΔG values were favorable for the formation of both types of inclusion complexes. The normal band of shorter wavelength (SW) appeared due to emission from locally excited (LE) state and was slightly blue-shifted. At the same time, the band of long wavelength (LW) was due to emission from the TICT, and was slightly red shifted. In the 1:1 complex, H8a, H8b and H13 protons of Benz imidazole moiety get in the cyclodextrin cavity, but in 1:2 complex, protons of H6 and H7 of pyridine ring in OMP also take part in complexation. These results were corroborated by molecular modeling calculations by PM3 method. This study recommends that HP-β-CD would be a suitable host to omeprazole for formulating various liquid and solid pharmaceuticals of the drug.