Different Effects of Forsythoside E on Acetylcholinesterase and Butyrylcholinesterase by Fluorescent Spectroscopy

Forsythoside E is one of the major secondary metabolites in Forsythia suspensa . The interactions between forsythoside E and two types of cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were investigated in PBS buffer (pH 7.40) by using multispectroscopic techniques. Forsythoside E increased the fluorescence intensity of AChE but quenched the fluorescence of BChE. Synchronous fluorescence studies showed that forsythoside E mainly acts on tyrosine residues of AChE and tryptophan residues of BChE. It was also proved that the complex between the compound and cholinesterases formed spontaneously at a stoichiometric ratio of 1:1 via multispectral technology. Finally, forsythoside E inhibited the activities of cholinesterases with similar IC 50 values of 1.08 mM for AChE and 0.92 mM for BChE. The results illuminate the details of the interaction between forsythoside E and cholinesterases.