Biological Activities of Chitin Oligosaccharides and Their Derivatives

Abstract

Chitin, a polymer of N-acetyl glucosamine (GlcNAc), (1-4)-linked 2-acetamido-2-deoxy-β-D-glucan, is widely distributed among invertebrates and crustaceans as structural material in their exoskeletons and fungal cell walls. Chitin and its derivatives have important biological properties that have potentials for a wide variety of applications such as immunostimulatory, enzyme inhibitory, antimicrobial, anticancer, anticholesteremic, anticoagulant and wound- healing agents. However, chitin is an insoluble polymer in water and this property is the major limiting factor for its utilization in living systems. Until now, there are few reports on biological activities of chitin oligosaccharides (NA-COSs) in live cells. The objectives of this research are to produce NA-COSs with different molecular weights which are soluble in water and to synthesize aminoethyl-chitooligosaccharide (AE-COS), a derivative of chitooligosaccharide (COS), with enhanced biological activities. Furthermore, their biological activities such as antioxidant, anti-inflammatory, and enzyme inhibitory activity were investigated. NA-COSs were produced by the hydrolysis of crab shells using hydrochloric acid and filtration through an ultrafiltration (UF) membrane with molecular weight cut off (MWCO) 3kDa and 1kDa. In addition, AE-COS was synthesized by grafting 2-chloroethylamino hydrochloride onto COS at C-6 position and their chemical structures and molecular weights (MW) were determined by FT-IR, NMR, and MALDI-TOF MS. Antioxidant activities of low MW NA-COS was observed in-vitro using electron spin resonance (ESR) spectroscopy. In cell system, NA-COS with MW range (1-3 kDa) exhibited higher antioxidant activities than NA-COS with the MW below (1kDa) and AE-COS higher than COS, respectively. They also showed inhibitory effect against reactive oxygen species (ROS) on activity of myeloperoxidase (MPO) and oxidation of DNA and protein. Furthermore, they decreased intracellular H₂O₂ level in 2′,7′-dichlorofluorescein (DCF) assay, but the intracellular glutathione (GSH) level was significantly increased in a time dependent manner. Both NA-COSs and AE-COS inhibit the production of nitric oxide (NO) and major inflammatory mediators. Anti-inflammatory effect of these compounds was observed via regulation of iNOS, COX-2, TNF-α, and IL-1β gene and protein expression in live cells exposed to bacterial lipopolysaccharide (LPS) in RT-PCR and Western blot analyses. Furthermore, NA-COSs and AE-COS showed the inhibitory effect on matrix metalloproteinases (MMP-2, -9) expression and angiotensin I converting enzyme (ACE), respectively. The present study provides a possible application of chitin oligosaccharides and their derivatives as food supplement, nutraceuticals, and cosmeceuticals because of their antioxidant activity. Furthermore, they can also be used as a therapeutic agent in the treatment of inflammatory diseases.