Inhibition of acetylcholinesterase by Solanum tuberosum glycoalkaloids: Integrated In Vivo evaluation, docking, molecular dynamics, and MM-GBSA analyses

Abstract

Glycoalkaloids from Solanum tuberosum have been found to inhibit acetylcholinesterase (AChE) and their concentrations tend to increase when exposed to light implicating the compound in both neurotoxic and therapeutic roles. The current work dealt with the bioaccumulation of glycoalkaloids in potatoes exposed to light, which determined the consequent in vivo inhibition of AChE, which, in particular, investigated the dynamical stability and binding energy of glycoalkaloids to AChE using molecular dynamics (MD) and MM-GBSA free energy calculations. Fresh tubers were exposed to natural ultraviolet sunlight for a period of four weeks, total glycoalkaloids (TGA) were quantified and then injected to male rats at a dose of 1-10 milligrams per kilogram with a negative control group of rats injected with a saline solution. AChE activity in brain homogenates was determined by an acetyl thiocholine assay. In silico , AChE (PDB ID 7E3H) was used to dock alpha-solanidine and alpha-α-α-chaconinee. PyRx, version 0.8. For MD simulations, (Donepezil (ID 3152), a-solanidine (PubChem 9529171), and donepezil (ID 1500) complex donepezil, and a-solanidine and the second ligands (PubChem 442971) were subjected to 100-nanosecond explicit solvent simulations (MD simulation) via the OPLS4/TIP3P force field with NPT ensemble, after Prime MM-GBSA analyses was done. Light exposure caused significant increase in TGA concentrations of 230-300 mg kg-1 and inhibition of AChE which is dose dependent causing maximal inhibition of 76.8 % at 10 mg/kg. Docking results showed high binding affinities, from alpha-solanidine (-9.2 kcal per mol), alpha-α-α-chaconineee (-9.1 kcal per mol), and Donepezil (-11.7 kcal per mol). MD simulations showed rapid equilibration; the protein Ca RMSD and rmsd showed little change of about 1.3-1.6 A for Donepezil and alpha solanine complex while that of 442971 showed RMSD more than 2.0 A after about 60 ns. Ligand RMSD values were as follows: Donepezil was below 3, a-solanidine varied between 5-7, 442971 went above 10 for transient dissociation. Hydrogen-bonds interaction was maintained for Donepezil (1-2 bonds) and alpha-solanidine (3-7 bonds), while it declined to near zero (40 nano seconds approximately) for 442971. MM-GBSA calculations ranked the binding free energies as follows: Donepezil (-31.48 +- 2.34 kcal/mol) > a-solanidine (-26.21 +-2.67 kcal/mol) > 442971 (-16.01 +- 3.12 kcal/mol). In silico ADMET profiling indicated poor oral absorption (low HIA), lack of BBB permeability, and P-gp substrate liability for α-solanine and α-chaconine, alongside predicted safety flags, suggesting limited CNS drug-likeness despite strong AChE binding Long period exposure to light leads to increased accumulation of GAKs in potato which in turn potently inhibited AChE activity in vivo . The results of the MD and free energy calculations confirm that a-solanidine is a more stable and energetically favourable scaffold compared to alpha-α-chaconine, but not as potent as Donepezil. These results draw attention to the two-fold consequences of exposure to high glycoalkaloid levels, and the implications of this in both the risk and potential therapeutic potential of cholinergic dysfunction.