Preparation, Characterization and Antioxidant Activity of Inclusion Complex of Bakuchiol with Hydroxypropyl-β-cyclodextrin

Bakuchiol isolated from Psoralea corylifolia is a naturally occurring prenylated phenolic monoterpene with a variety of bioactivities. The aim of this study was to improve the water solubility and thermal stability of bakuchiol through complexing it with hydroxypropyl-β-cyclodextrin(HP-β-CD). The bakuchiol/HP-β-CD inclusion complex’s behavior and characterization were investigated by ultraviolet-visible(UV-vis) spectroscopy, Fourier transform infrared spectroscopy(FT-IR), thermogravimetric analysis(TGA),X-ray diffraction(XRD),~1H nuclear magnetic resonance(NMR), and two-dimensional(2 D) NMR. The obtained results indicated the formation of 1∶1 inclusion complex for bakuchiol with HP-β-CD. Water solubility of bakuchiol was significantly improved by complexation with HP-β-CD as demonstrated by phase solubility studies. The encapsulation of bakuchiol was confirmed by UV-vis, FT-IR, and XRD. The thermal stability was effectively enhanced by TGA and derivative thermogravimetry(DTG) analysis. In vitro antioxidant activity showed that bakuchiol/HP-β-CD inclusion complex had a little higher antioxidant ability than free bakuchiol. Moreover, we got the possible inclusion mode for the bakuchiol/HP-β-CD inclusion complex through NMR analysis. These results suggest that the inclusion complex can be a potentially useful approach in the design of novel formulations of bakuchiol for medical applications.