Characterization and enhanced antioxidant activity of the inclusion complexes of baicalin with p-sulfonatocalix[n]arenes

Baicalin, one of the main active constituents of the isolated root of Scutellaria baicalensis. It has many health-promoting properties. However, it is easy to be oxidized that impedes its application in the practical life. In this study, the inclusion complexes of baicalin with p-sulfonatocalix[n]arenes were studied by fluorescence spectroscopy, ultraviolet-visible spectroscopy (UV-vis), fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and atomic force microscopy. The results showed that baicalin was able to form inclusion complexes with p-sulfonatocalix[n]arenes in a molar ratio of 1:1 and the association constants (K) were different at different pH. Meanwhile, the antioxidant ability and stability experiments of baicalin and the inclusion complexes were done. The experimental results indicated that both the stability and the antioxidant activity of baicalin significantly increased by the formation of inclusion complexes with p-sulfonatocalix[n]arenes.