ARTICLE; PHARMACEUTICAL BIOTECHNOLOGY Binding of dihydromyricetin and its metal ion complexes with bovine serum albumin

The binding mechanisms of the interaction of three dihydromyricetin (DMY)metal complexes (DMYCu (II) complex, DMYMn (II) complex, DMYZn (II) complex) and DMY with bovine serum albumin (BSA) were investigated using fluorescence and ultraviolet spectroscopy at different temperatures. The results indicated some differences in the binding process between different DMYmetal complexes and BSA compared with that of free DMY. All of the complexes and DMY quenched the fluorescence of BSA based on static mode combined with radiationless energy transfer, yet having different binding distance based on the F€orster theory. Different DMYmetal complexes can change the binding constants. The binding constants increase for DMYCu (II) and DMYMn (II) complexes, whereas the opposite is true for the DMYZn (II) complex compared to the one with free DMY. The DMYmetal complexes can also affect the types of the interaction. The van der Waals forces and hydrogen bonding may play a major role in the interaction of free DMY with BSA, while for the three complexes, the nature of the binding forces lies in hydrophobic forces and hydrogen bonding based on the thermodynamic parameters