Preparation and physicochemical characterization of the supramolecular inclusion complex of naringin dihydrochalcone and hydroxypropyl-β-cyclodextrin

Naringin dihydrochalcone (naringin DC) is an intense sweetener and a strong antioxidant with potential applications in many food and pharmaceutical products. However, its low water solubility impedes the realization of these applications. This study investigated the feasibility of using hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to form a supramolecular inclusion complex with naringin DC to improve its solubility. The inclusion complex was prepared by stirring an equal molar solution of naringin DC and HP-beta-CD at 30 degrees C for 24 h, followed by freeze-drying. The resultant complex was characterized by ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetty (DSC), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and proton nuclear magnetic resonance spectroscopy (H-1-NMR) to determine its spectral, phase transitional and morphological properties and to elucidate its conformational structure. Results showed clearly the formation of a supramolecular complex in which the guest molecule, naringin DC, was entrapped inside the cavity of the host, HP-beta-CD. The close association between naringin DC and HP-beta-CD resulted in changes in some of the characteristic spectral, phase transitional and morphological properties of naringin DC. Furthermore, H-1-NMR analyses demonstrated that it was the B ring of naringin DC that was inserted into the HP-beta-CD cavity to form the supramolecular complex. (C) 2013 Elsevier Ltd. All rights reserved.