Isatin derived morpholine and piperazine derivatives as acetylcholinesterase inhibitors

The present study focus on the design and synthesis of two classes of hydrazones of isatin derivatives bearing morpholine and piperazine units (IHP1-IHP6 and IHM1-IHM6). The molecules have been further investigated for their in vitro cholinesterases inhibition studies. As per the enzyme inhibition study, IHM2 showed high inhibitory activity against hAChE with an IC50 value of 1.60 ± 0.51 μM indicating that substitution of chlorine at C-5 position of isatin ring and presence of morpholine moiety displayed the higher inhibitory activity towards hAChE. The lead molecules were further evaluated for their CNS druglikeness by using PAMPA assay. As from the PAMPA assay, it was demonstrated that IHM2 showed significant CNS permeability having Pe value greater than 4.0×10⁻⁶ cm/s. Docking studies, performed to understand the binding mode of IHM2 with hAChE, resulted in a docking score of -10.250 kcal/mol, with the compound showing hydrogen bonding with Phe 295, Ser 293 and pi-pi stacking interaction with Phe 338. Molecular dynamics simulations indicated a significant stability of IHM2-hAChE complex over a time period of 100 ns. In addition, IHM2 possess favourable ADME properties with goog blood-brain barrier permeability. Overall, lead molecule IHM2 could be a promising AChE inhibitor to treat various neurodegenerative disorders.