The Interaction Between Two Metabolites of Polygala tenuifolia and Cholinesterases

Abstract

Objective: The work aimed to compare the binding between the two main components of Polygala tenuifolia Willd. and two cholinesterases (ChEs) by using a variety of spectral techniques. Methods: Two main components of Polygala tenuifolia Willd. included Tenuifolin (Ten) and Onjisaponin B (Onj B), and two ChEs included acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Results: The UV-visible absorption spectra results showed that Ten had no effect on the structure of ChEs, and the combination of Onj B with ChEs changed its structure. Onj B statically quenched the endogenous fluorescence of both of ChEs, Ten dynamically quenched the endogenous fluorescence of AChE with no effect on BChE. The fluorescence quenching rate of ChEs by Onj B was much higher than that of AChE by Ten, and only one binding site of each protein spontaneously interacted with the compound to bind to or collide. Synchronous fluorescence results showed that Ten and Onj B quenched the fluorescence intensity by affecting tryptophan and tyrosine residues in cholinesterases, respectively. Hydrophobic force played an important role in the interaction between Ten and AChE, and van der Waals force and hydrogen bond were the main driving forces for the binding of Onj B to ChEs. The Enzyme activity test showed that Onj B inhibited ChE activity, and Ten never inhibited ChE activity. Conclusion: Onj B has the potential to inhibit ChE activity and increase the neurotransmitter acetylcholine content in the nerve system, improving the Alzheimer's disease (AD).