Some heterocycles connected to substituted piperazine by 1,3,4-oxadiazole linker: Design, synthesis, anticholinesterase and antioxidant activity

Abstract

AD is a multifactorial neurodegenerative disease that has caused morbidity and mortality on a global scale. Currently, there are only a few drugs used in the treatment of AD. Although many compounds that aim at new targets have reached clinical trials, none have been approved. However, discovering efficient drugs for AD treatment is one of the biggest challenges for pharmaceutical research and requires strong support. In this paper, we aim to design a series of indole, benzothiophene, and thiophene bearing 1,3,4-oxadiazole linker to the piperazine basic center and evaluate for their antioxidant and inhibitory activity against both cholinesterase enzymes. Among the compounds, 6a, 7b, and 8b exhibited moderate cationic radical scavenging activities with IC50 values ranging from 20.39 to 30.10 μM. The inhibitory activity results revealed that compounds 5c (IC50 for AChE = 53.91 μM and for BChE = 55.81 μM) and 6c (IC50 for AChE = 54.42 μM and BChE = 45.82 μM) bearing 2-fluorophenyl piperazine moiety showed both AChE and BChE inhibition with moderate IC50 values. To explore the binding properties of the target compounds into the active site of the enzyme, a molecular docking study was carried out using MOE software. The docking study showed that compound 6c targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE/BChE and formed important interactions with key residues. Moreover, theoretical physicochemical properties of the best active compound 6c were calculated by the SwissADME web service. It obeyed Lipinski's rule of five and had high GI absorption (gastrointestinal absorption) and good permeating to the blood-brain barrier (BBB). The compound 6c can be considered a promising compound and provides us directions for further research of anti-AD agent development.