Recent Studies on Heterocyclic Cholinesterase Inhibitors Against Alzheimer's Disease.

Alzheimer's disease is a progressive and neurodegenerative disease characterized by impairment in emotion, language, memory, and cognitive judgment. There are many factors related to Alzheimer's disease, such as amyloid beta plaques (Aβ) due to impaired metabolism of amyloid precursor protein (APP), tau hyperphosphorylation, and accumulation of neurofibrillary tangles, and disruption of the cholinergic system. Disruption of the cholinergic system responsible for cognitive function and memory processes is one of the important causes of Alzheimer's disease. Therefore, cholinesterase (acetylcholinesterase and butyrylcholinesterase) inhibitors that maintain choline (acetylcholine and butyrylcholine) levels in the synaptic gap play an important role in the symptomatic treatment of Alzheimer's disease. Numerous studies have been carried out against Alzheimer's disease involving acetylcholinesterase and butyrylcholinesterase inhibitors. However, there are very few drugs (tacrine, rivastigmine, galantamine, and donepezil) approved as cholinesterase inhibitors. Therefore, cholinesterase inhibitors are needed against Alzheimer's disease. This review is focused on using heterocyclic rings that show remarkable cholinesterase inhibitory activity for Alzheimer's disease. In this review, chemical structures and structure-activity relationships of recently reported cholinesterase inhibitors are emphasized. This review will give important ideas to medicinal chemists in the discovery and development of potent cholinesterase inhibitors in their future studies.