Multispectroscopic and computational evaluation of the binding of flavonoids with bovine serum albumin in the presence of Cu2+

Bovine serum albumin (BSA) has the potential application of establishing a delivery system for flavonoids. However, the effect of copper on the binding of flavonoids with BSA is unclear. Therefore, the binding of six flavonoids with BSA containing Cu 2+ was investigated using UV–vis, fluorescence, and molecular docking. The UV–vis spectral changes demonstrated the formation of flavonoid-Cu 2+ complexes. The fluorescence quenching results suggested that the chelation of Cu 2+ increased the binding affinity of galangin and baicalin to the BSA but decreased the binding capacity of chrysin, baicalein, luteolin, and vitexin. Synchronous fluorescence data revealed that Cu 2+ could influence the secondary structure conformation of BSA binding with flavonoids, which was further confirmed by ANS-binding fluorescence, circular dichroism, and molecular docking. These findings demonstrate that the complexation of Cu 2+ significantly affects the binding of flavonoids with BSA, which provides the theoretical basis for the development of natural product-metal complex functional foods.