Molecular interaction studies of acetylcholinesterase with potential acetylcholinesterase inhibitors from the root of Rhodiola crenulata using molecular docking and isothermal titration calorimetry methods

(-)-Epicatechin gallate ((-)-ECG), 1,2,3,4,6-O-pentagalloylglucose (PGG), rhodionin, herbacetin and rhodiosin isolated from the root of Rhodiola crenulata exhibited potent, dose-dependent inhibitory effects on acetylcholinesterase (AChE) with IC₅₀ ranged from 57.50±5.83 to 2.43±0.34μg/mL. With the aim of explaining the differences in activity of these active ingredients and clarifying how they inhibit AChE, the AChE-inhibitor interactions were further explored using molecular docking and isothermal titration calorimetry (ITC) methods in the present study. Molecular docking studies revealed that all compounds except PGG showed binding energy values ranging from -10.30 to -8.00kcal/mol while the binding energy of galantamine, a known AChE Inhibitor, was -9.53kcal/mol; they inhibited the AChE by binding into the ligand pocket with the similar binding pattern to that of galantamine by interacting with Glu199 of AChE. Inhibition constant of these active ingredients had a positive correlation with binding energy. The interaction between AChE and PGG was further evaluated with the ITC method and the results indicated that the PGG-AChE interaction was relevant to AChE concentration. The results revealed a possible mechanism for the AChE inhibition activity of these bioactive ingredients, which may provide some help in lead compounds optimization in the future.