DFT Studies and Acetylcholinesterase Inhibition Capacity Analysis of an Adamantane-Isothiourea Derivative via Docking and MD Calculations

In this work, 4-bromobenzyl(Z)-N'-(adamantan-1-yl)-4-phenylpiperazine-1-carbothioimidate (4BAPC), an adamantane-isothiourea derivative, was studied through density functional theory (DFT) at the M06-2X/6 − 311 + G(2df,2p) level of theory, where its structural, vibrational, and quantum-chemical properties were comprehensively described. The analysis of the IR and Raman frequencies, with the help of potential energy distribution (PED) calculation, allowed the assignment of several characteristic vibrations that may be used in the identification of other adamantane-isothiourea derivatives. Solvation-free energy (SFE) calculations in water, ethanol, acetone, and chloroform were carried out, where acetone and chloroform showed the most negative values, −23.34 and −23.33 kcal/mol, respectively, suggesting that these two solvents better solubilize 4BAPC. Also, the SFE value in water, −10.49 kcal/mol, indicates good solubility in an aqueous medium. FMOs, MEP, ALIE surfaces, and Fukui indices calculations allowed to identify that the most reactive sites of 4BAPC comprise the aromatic rings and piperazine moiety. Acetylcholinesterase (AChE) inhibition capacity presented by 4BAPC was evaluated through molecular docking and molecular dynamics (MD) calculations. Docking binding affinity and MMPBSA binding energy showed, respectively, values of −9.2 and −29.954 kcal/mol, which indicates strong evidence for the AChE inhibitory potential by 4BAPC.