Characterization and Enhanced Antioxidant Activity of the Cysteinyl ß-Cyclodextrin-Baicalein Inclusion Complex.

Baicalein is a type of flavonoid isolated from the roots of a medicinal plant, Scutellaria baicalensis. Although it has attracted considerable attention due to its antiviral, anti-tumor, and anti-inflammatory activities, its limited aqueous solubility inhibits the clinical application of this flavonoid. The present study aimed to prepare and characterize a host-guest complex in an effort to improve the solubility and antioxidant activity of baicalein. The host molecule is a macrocyclic ß-cyclodextrin (ß-CD) functionalized with cysteine for a synergetic effect. The structure of the synthesized cysteinyl ß-CD was analyzed using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The inclusion complex with baicalein was studied by UV-vis, NMR spectroscopy, scanning electron microscopy, and X-ray powder diffractometry. The formed cysteinyl ß-CD/baicalein inclusion complex efficiently improved the solubility and antioxidant ability of baicalein. Therefore, we suggest that the present cysteinyl ß-CD is a potential host molecule for inclusion complexation and for bioavailability augmentation.