A comprehensive review on therapeutics and diagnostic agents targeting acetyl and butyryl cholinesterases for AD.

Alzheimer's disease (AD) is a progressive, irreversible, and multifaceted neurodegenerative disorder characterized by cognitive decline, memory loss, and behavioral impairment, posing a major global health challenge. Its multifactorial pathology includes cholinergic dysfunction, amyloid-β deposition, tau hyperphosphorylation, oxidative stress, and neuroinflammation. Among these, impairment of the cholinergic system, characterized by reduced acetylcholine levels, plays a crucial role in cognitive deficits. The enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), which hydrolyze acetylcholine, are closely involved in disease progression and serve as important therapeutic and diagnostic targets in AD. This book chapter provides a comprehensive overview of therapeutic and diagnostic agents targeting AChE and BChE in AD, and discusses small-molecule inhibitors, multifunctional ligands, and emerging strategies to modulate cholinesterase activity and restore cholinergic neurotransmission, alleviating disease symptoms. In addition, the chapter highlights advances in diagnostic approaches using fluorescent probes, particularly near-infrared (NIR) probes, for selective detection and imaging of AChE and BChE, including their molecular design, photophysical properties, enzyme selectivity, and mechanisms of action, all of which are critically examined. Targeting AChE and BChE offers a dual advantage in AD by enabling both symptomatic treatment and early-stage diagnosis. This chapter aims to present a clear and comprehensive overview of recent advances in therapeutic and diagnostic approaches, offering meaningful insights for researchers in developing effective strategies for the treatment and monitoring of AD.