chitooligosaccharides

Chitooligosaccharides (COS) are low molecular weight oligomers derived from chitin or chitosan. They consist of short chains of β-(1→4)-linked units of D-glucosamine (GlcN) and N-acetyl-D-glucosamine (GlcNAc). COS typically have a degree of polymerization (DP) of about 2 to 20, though distributions up to 50 have been reported depending on source and preparation. They are more water-soluble than the parent polymers, and their physicochemical properties depend on the degree of acetylation (DA) and pH.

COS are produced by acid hydrolysis of chitin or chitosan or by enzymatic degradation using chitinases or chitosanases. Purification yields fractions with defined DP and acetylation patterns. The pattern of acetylation, whether random or blocky, and the overall DA influence solubility, conformation, and biological activity.

Biological activities of COS have been reported across plants, microbes, and animals. In plants, COS can act as defense elicitors and stimulate resistance responses. In microbes and animals, they show antimicrobial and antifungal activity, antioxidant effects, anti-inflammatory and immunomodulatory potential, and, in some contexts, antiviral activity. COS also conform to uses as biomaterial carriers for drug delivery and as components in wound dressings, cosmetics, and functional foods. Their effects are often concentration- and context-dependent and depend on DP, DA, and pattern of acetylation.

Safety and regulation vary by application and jurisdiction. COS are generally regarded as biocompatible and have been investigated for agricultural, pharmaceutical, and cosmetic uses, but standardization of size, composition, and purity remains a challenge. When used, safety assessments and labeling should reflect their origin from chitin/chitosan, derived from crustacean sources in some cases.