Preparation, characterization and binding behaviors of host-guest inclusion complexes of metoclopramide hydrochloride with α- and β-cyclodextrin molecules

Abstract

The supramolecular interaction of metoclopramide hydrochloride (MP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) has been inspected by ultraviolet–visible (UV–vis) light, infra-red (IR) light, fluorescence and 1H NMR spectroscopy. The formation of an inclusion complex greatly affects the physical–chemical properties of the guest molecules, such as solubility, chemical reactivity and the spectroscopic and electrochemical properties. Thus the changes in the spectral properties and physico-chemical properties confirm the inclusion complex formation. Surface tension, conductivity studies and Job's plot indicate a 1: 1 stoichiometry of the MP:CD host–guest inclusion complexes. The binding/association constants have been evaluated by both UV–Vis and fluorescence spectroscopic study indicating a higher degree of encapsulation for β-cyclodextrin (β-CD). Furthermore, the negative value of thermodynamic parameter (ΔG°) of the host-guest system suggests that the inclusion process proceeded spontaneously at 298.15 K. Based on the NMR data, the plausible mode of interaction of MP:α-CD and MP:β-CD complexes were proposed, which suggested that lipophilic aromatic ring of the MP entered into the cavity of CDs from the wider side, with the amide (CONH) and methoxy (-OMe) residues inside the CD cavity.