Inclusion Effect and Solution Properties of Hydroxypropyl-β-Cyclodextrin on Ferulic-Nicotinamide Cocrystal

To investigate the effect of the inclusion interaction of cyclodextrin-based materials on the properties of plant active substances, ferulic acid-nicotinamide cocrystal（FA-NIC）/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complexes were prepared. The inclusion behavior of HP-β-CD towards FA-NIC cocrystals and the solution properties were studied. Phase solubility curves and Job’s plots indicated that FA-NIC cocrystals form inclusion complexes with HP-β-CD at a molar ratio of 1∶1. Results from X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy demonstrated that hydrogen bonding interactions exist between the FA-NIC cocrystals encapsulated in the hydrophobic cavity of HP-β-CD and the hydroxyl groups of HP-β-CD. Due to the hydrophobic interactions between the C−H bonds and glycosidic bonds in the hydrophobic cavity of HP-β-CD and FA-NIC cocrystals, FA exhibited enhanced ultraviolet (UV) absorption and fluorescence intensity. Compared with pure FA, the equilibrium solubility in water, UV light stability, and DPPH（1,1-diphenyl-2-picrylhydrazyl） free radical scavenging rate of FA in the FA-NIC/HP-β-CD inclusion complex were increased by 5.7-fold, 17.9 percentage points, and approximately 1-fold, respectively.