Abstract: In order to select a suitable cyclodextrin (CD) for the inclusion complexation of glabridin (GLD), the inclusion capacity of different CDs for GLD was studied by molecular docking and phase solubility method. The effects of different drying methods and GLD/CD ratios on the inclusion rate, drug loading and solubility of solid inclusion complexes were investigated. The morphology of inclusion complexes, the existing form of GLD in inclusion complexes, the interaction between GLD and CD and the spatial conformation of inclusion complexes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and molecular docking, respectively. The dissolution properties of GLD before and after inclusion complexation were investigated by in vitro dissolution experiments. Methylthiazolyl tetrazolium (MTT) assay was used to compare the inhibitory effect of GLD and its inclusion complexes on the proliferation of human hepatoma cell line (HepG-2). The results showed that various CDs could form 1:1 inclusion complexes with GLD, and 2-sulfobutyl-β-CD (2-SBE-β-CD) had a better capability to include GLD than other CDs and their derivatives. There was no significant difference in the inclusion rate or drug loading of GLD/2-SBE-β-CD solid inclusion complexes prepared by different preparation methods, but the water solubility of the inclusion complexes was different. Appropriately increasing the ratio of GLD to 2-SBE-β-CD reduced the inclusion rate to a certain extent but significantly increased the drug loading. The inclusion rate and drug loading of the GLD/2-SBE-β-CD solid inclusion complex prepared with a 1.5:1 molar ratio between GLD and 2-SBE-β-CD by freeze-drying method were 86.09% and 22.39%, respectively. The saturated solubility of the inclusion compounds prepared with a 1:1 molar ratio between GLD and 2-SBE-β-CD by freeze-drying, spray-drying and kneading were all greater than 83 mg/mL. These inclusion complexes had significantly different morphology, but GLD existed in an amorphous structure in all of them. However, there was no significant difference in the dissolution properties of the inclusion complexes. The cumulative dissolution rates of the GLD/2-SBE-β-CD inclusion complexes in gastric and intestinal fluid were significantly higher than that of GLD and its physical mixture with 2-SBE-β-CD. The GLD/2-SBE-β-CD inclusion complexes had significantly enhanced anti-proliferative activity on HepG-2 cells compared with GLD/H2O. The results of this study confirm that the superiority of 2-SBE-β-CD as a GLD carrier is expected to broaden the application of GLD in food, health products and other fields.

Key words: glabridin; cyclodextrin; solid inclusion complex; preparation; optimization; characterization; dissolution; anti-cell proliferation activity