Characterization of glabridin/hydroxypropyl-β-cyclodextrin inclusion complex with robust solubility and enhanced bioactivity

Various biological activities of glabridin have been reported in literature, however, the bioavailability and clinical application was limited by its low water solubility. In this study, we developed a novel inclusion complex of glabridin and hydroxypropyl-β-cyclodextrin (HP-β-CD) that features improved solubility and bioactivity. The formation of the inclusion complex was supported by data from FT-IR, PXRD, SEM and NMR. Specifically, the NMR results indicated that the aromatic ring of glabridin was merged into and located at the narrow side the cavity of HP-β-CD. The in vitro tests showed that the formation of the inclusion complex led to 9 times increase in the DPPH radical-scavenging capacity and 20 times increase in the tyrosinase inhibitory activity compared to the free glabridin at the same concentration. Therefore, the glabridin/HP-β-CD inclusion complex adds a promising strategy for the clinical application of glabridin in the future.