Formation of Inclusion Complexes of 2-Hydroxypropyl β-Cyclodextrin with 2-Hydroxychalcone: Experimental and Theoretical Study

The formation of inclusion complexes of 2-hydroxypropyl-β-cyclodextrin (HP β-CD) with 2-hydroxychalcone (2HOCH) in solution and solid state was investigated using UV–Visible, fluorescence, Fourier transform-infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscope (SEM) techniques. The results obtained confirmed that 2HOCH formed the stable inclusion complex with HP β-CD. Moreover, the spectral data and Benesi–Hildebrand plots results indicated that the stoichiometry of the inclusion complex was 1:1. Theoretically, the structure of the inclusion complexes and the physical parameters such as complexation energy, highest occupied molecular orbital–lowest unoccupied molecular orbital, and energy gap were obtained using the DFT/B3LYP/6-311G method. It was found that the complexation energy for orientation B was lower than that for orientation A as evidenced by the theoretical calculations. Moreover, the carbonyl group of molecules was located outside of the cyclodextrin cavity while the hydroxyl group was located inside the cavity. The antioxidant capacity and antibacterial responses of the inclusion complexes and, for comparison, the parent compounds were also carried out.