Proposing novel natural compounds against Alzheimer's disease targeting acetylcholinesterase.

Alzheimer's disease (AD) is a neurodegenerative disorder considered as a global public health threat influencing many people. Despite the concerning rise in the affected population, there is still a shortage of potent and safe therapeutic agents. The aim of this research is to discover novel natural source molecules with high therapeutic effects, stability and less toxicity for the treatment of AD, specifically targeting acetylcholinesterase (AChE). This research can be divided into two steps: in silico search for molecules by systematic simulations and in vitro experimental validations. We identified five leading compounds, namely Queuine, Etoperidone, Thiamine, Ademetionine and Tetrahydrofolic acid by screening natural molecule database, conducting molecular docking and druggability evaluations. Stability of the complexes were investigated by Molecular Dynamics simulations and free energy calculations were conducted by Molecular Mechanics Generalized Born Surface Area method. All five complexes were stable within the binding catalytic site (CAS) of AChE, with the exception of Queuine which remains stable on the peripheral site (PAS). On the other hand Etoperidone both interacts with CAS and PAS sites showing dual binding properties. Binding free energy values of Queuine and Etoperidone were -71.9 and -91.0 kcal/mol respectively, being comparable to control molecules Galantamine (-71.3 kcal/mol) and Donepezil (-80.9 kcal/mol). Computational results were validated through in vitro experiments using the SH-SY5Y(neuroblastoma) cell line with Real Time Cell Analysis (RTCA) and cell viability assays. The results showed that the selected doses were effective with half inhibitory concentrations estimated to be: Queuine (IC50 = 70,90 μM), Etoperidone (IC50 = 712,80 μM), Thiamine (IC50 = 18780,34 μM), Galantamine (IC50 = 556,01 μM) and Donepezil (IC50 = 222,23 μM), respectively. The promising results for these molecules suggest the development of the next step in vivo animal testing and provide hope for natural therapeutic aids in the treatment of AD.