Chitosan oligosaccharide (COS): An overview

The frequently studied polysaccharide, chitosan oligosaccharide/chitooligosaccharide (COS) is the major degradation product of chitosan/chitin via chemical hydrolysis or enzymatic degradation involving deacetylation and depolymerization processes. Innumerable studies have revealed in the recent decade that COS has various promising biomedical implications in the past analysis, current developments and potential applications in a biomedical, pharmaceutical and agricultural sector. Innovations into COS derivatization has broadened its application in cosmeceutical and nutraceutical productions as well as in water treatment and environmental safety. In relation to its parent biomaterials and other available polysaccharides, COS has low molecular weight (Mw), higher degree of deacetylation (DD), higher degree of polymerization (DP), less viscous and complete water solubility, which endowed it with significant biological properties like antimicrobial, antioxidant, anti-inflammatory and antihypertensive, as well as drug/DNA delivery ability. In addition, it is also revealed to exhibit antidiabetic, anti-obesity, anti-HIV-1, anti-Alzheimer's disease, hypocholesterolemic, calcium absorption and hemostatic effects. Furthermore, COS is shown to have higher cellular transduction and completely absorbable via intestinal epithelium due to its cationic sphere exposed on the more exposed shorter N-glucosamine (N-Glc) units. This paper narrates the recent developments in COS biomedical applications while paying considerable attention to its physicochemical properties and its chemical composition. Its pharmacokinetic aspects are also briefly discussed while highlighting potential overdose or lethal dosing. In addition, due to its multiple NGlc unit composition and vulnerability to degradation, its safety is given significant attention. Finally, a suggestion is made for extensive study on COS anti-HIV effects with well-refined batches. •COS physicochemical properties and reactive functional groups are highlighted as correlated to chemical modifications.•Pharmacokinetic aspects of COS and its derivatives with insight into therapeutic dosage formulations.•COS multiple biological activities and promising biomedical applications with recent developments are narrated.•Anti-HIV-1 effects of COS are scarcely studied, thus suggested for in-depth study.•Thorough safety and chemical analysis is crucially suggested with COS exposure to chemical, enzymatic and thermal exposure.