Preparation, characterization and solubilization evaluation of two novel host-guest complexes based on two different functional groups of modified β-cyclodextrins and 20(S)-protopanaxatriol

Due to the poor solubility of 20(S)-protopanaxatriol (PPT), its application was seriously limited. To solve the problems, a novel mono [6-(1,3-diamino-2-hydroxy)-propyl-6-deoxyl-beta-CD (H1) was designed and synthesized. The two inclusion complexes of H1 and mono [6-(3,3'-oxybis (ethyleneoxy)bis (propylamino))-6-deoxyl-beta-CD (H2) with PPT were prepared and characterized by UV, NMR, FT-IR, XRD and SEM. The Job's method indicates that the stoichiometry of all inclusion complexes were 1:1. The ROESY spectrum demonstrated that the A-ring and B-ring of PPT integrated into the H1 cavity, and the side chain of H1 is shallowly self-included into the CD cavity. Meanwhile, the A-ring of PPT partly penetrate into H2 cavity, while the side chain of H2 is deeply self-included into the CD cavity through the inducedfit interaction. UV-Vis spectral demonstrated that the complex stability constant (K-S) of H2 towards PPT was higher than that of H1. The binding ability is discussed according to the size/shape fit concept and hydrogen bond interaction between host and guest. The water solubility of PPT is significantly increased 133 and 532 times after inclusion of H1 and H2, respectively. Therefore, the H1 and H2 can improve the solubility of PPT, broadening the field of application in herbal medicine and health protection foods. (C) 2019 Elsevier B.V. All rights reserved.