Study of the interactions of forsythiaside and rutin with acetylcholinesterase (AChE).

Acetylcholinesterase (AChE) inhibitors have been considered as candidates for the treatment of Alzheimer's disease (AD) and have been utilized in clinical trials. In the present study, the interactions of forsythiaside and rutin with AChE have been investigated, after discovering the inhibitory AChE activity of the two compounds. Forsythiaside and rutin both can bind to AChE to form forsythiaside-AChE and rutin-AChE complex, and thus quench the intrinsic fluorescence of AChE. The quenching mechanism, the binding sites, the binding forces, the binding constants and the energy transfer involved were studied in details. Forsythiaside and rutin show some properties in common, including the stoichiometric binding ratio of 1:1 with AChE and the full quenching of AChE fluorescence. At the same time, the two compounds distinctly present some different characters, for example, the binding constant of rutin is less than that of forsythiaside, and the interaction force and the affinity between forsythiaside and AChE are much bigger than that of rutin. Spectroscopy data and docking analysis powerfully support the findings that forsythiaside inhibit AChE activity more strongly than rutin. The current study will provide the better understanding on the nature of the possible interactions between forsythiaside and rutin with AChE.