Study on inclusion behavior of tangeretin with β-cyclodextrin and its derivatives

Using β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin and 2, 3, 6-trimethyl-β-cyclodextrin as the host and tangeretin (TAN) as the guest, three new host-guest inclusion complexes were successfully prepared by the saturated solution method. The host-guest inclusion complexes were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). The possible inclusion mode of the inclusion complexes were deduced by proton nuclear magnetic resonance spectroscopy (¹H NMR, 2D NMR) and molecular docking calculations. The inclusion stoichiometric ratio, water solubility and stability of TAN and three cyclodextrins were studied by ultraviolet-visible spectroscopy (UV-Vis). The experimental results showed that the three inclusion complexes were successfully prepared. The inclusion host-guest stoichiometric ratio was 1∶1. The TAN entered the cavity from the wide side end of the cyclodextrin by the A ring of the TAN, and the TAN penetrated the cavity of CDs. In addition, TAN and three kinds of cyclodextrins are easier to form inclusion complexes at pH=3.0. The water solubility and stability of TAN were significantly improved after inclusion, which provided a theoretical basis for the pharmaceutical preparation of TAN.