Role of triterpenoid derivatives from Centella asiatica as quantum chemical calculations

To date, the treatment for Alzheimer's disease (AD) has focused on the cholinergic hypothesis, particularly through the inhibition of acetylcholinesterase (AChE). Asiatic acid, madecassic acid, asiaticoside, and madecassoside, which are triterpenoid derivatives from Centella asiatica, have previously been reported to exhibit the AChE inhibitory activity. This study aimed to investigate their binding modes and to determine efficient computational methods for analyzing their interactions with AChE. Molecular dynamics simulations demonstrated that most of their equilibrated structures remained within the AChE binding site. Principal component analysis and free energy landscape (FEL) confirmed their stability of the binding. Among the evaluated methods, the MM-(ALPB)SA binding energies, when combined with ligand surface binding efficiency index, showed the best correlation with experimental binding free energy. Density functional theory (DFT) calculations revealed the common key interaction between triterpenoids and AChE, including hydrogen bonds (Tyr124, Arg296, Tyr337, and Tyr341), H-π (Tyr341) and van der Waals (Trp86) interactions. Additionally, pharmacokinetics and drug-likeness predictions indicated that madecassic acid and asiatic acid are promising candidates for drug development. This study highlights the potential of triterpenoid derivatives in AChE inhibition and provides valuable insights into their binding efficiency, which could contribute to future drug discovery targeting Alzheimer's disease.