Inclusion complex of quercetin with sulfobutylether β-cyclodextrin: preparation, characterization, antioxidant and antibacterial activities and the inclusion mechanism

Quercetin (QCT) has a variety of pharmacological effects, such as antioxidant, antibacterial, anticancer, anticardiovascular and antiaging effects. However, its poor water solubility, stability and bioavailability limit its applications. The special structure of cyclodextrins and their derivatives with a hydrophobic inner cavity and hydrophilic outer wall can load a variety of hydrophobic drugs of a suitable size and shape, thereby improving the stability and solubility of these molecules. In this study, an inclusion complex of quercetin and sulfobutylether-β-cyclodextrin was prepared. It was characterized via FT-IR, UV, 1 H NMR, XRD, DSC, and SEM analysis, which revealed the successful formation of the inclusion complex. In vitro biological activity estimations were carried out and the results indicated that the inclusion complex displayed higher antioxidative and antibacterial properties compared with free QCT. In addition, the mechanisms of inclusion were explored using 1 H NMR analysis and docking calculations, thus providing a theoretical basis for obtaining an inclusion complex. Sulfobutylether β-cyclodextrin can significantly improve the antioxidant and antibacterial activities of quercetin through the formation of an inclusion complex, and their interactions have been elucidated.