Marine‐Derived Chitosan Oligosaccharides and Their Derivatives: A New Hope for Alzheimer's Prevention and Treatment – A Critical Review

Alzheimer's disease (AD) is a progressive degenerative disease of the central nervous system. Its clinical manifestations are mainly cognitive and memory disorders, and its incidence rate and mortality are increasing year by year. Chitosan oligosaccharides (COS), also known as β-1,4-oligoglucosamine, are natural alkaline polysaccharides and the only positively charged ones in nature. Due to its low molecular weight, good water solubility, and excellent biocompatibility, non-toxicity, and biodegradability, in recent years, it has received increasing attention from domestic and foreign researchers and enterprises. COS is of great significance in the prevention and treatment of AD; the main mechanisms of action include inhibiting acetylcholinesterase and beta-secretase activity, preventing abnormal phosphorylation of tau protein, chelating copper ions, protecting neuronal cells, and exhibiting antioxidant effects. This review primarily combines the latest research results, both domestic and international, to summarize and analyze the anti-AD effects and possible mechanisms of COS, aiming to provide the theoretical basis and the reference for the in-depth study of COS in the fields of biomedicine and functional foods and for its wider application in the fields of medicine and health food.