Determination of Physicochemical Parameters and Structural Elucidation of Crab-shell Chitosan, and Antioxidant Activity Study of Oligochitosan-encapsulated Crab-shell Chitosan

Chitin obtained after demineralization and deproteinization of pulverized crab shells was deacetylated in strictly alkaline medium of caustic soda to yield high molecular weight nano-crystalline crab-shell chitosan (HMWNC) with Mw of 350 kDa, 71% DDA, particle size of 76 nm, 7.4% moisture content and 1% ash content. The current work involved encapsulation of commercial chitosan oligosaccharide (COS) with average Mw < 3000 Da and 87% DDA in HMWNC, and such an encapsulation of COS as a pharmaceutical ingredient into HMWNC was carried out to bring about an enhancement in bioavailability of COS in target cells. This was revealed by higher in vitro antioxidant activity of HMWNC encapsulated chitosan oligosaccharide (COS-HMWNC) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals (IC50 = 512.6±14.4 g/mL) than COS and HMWNC with less than 50% inhibition at 1000 g/mL. The antioxidant t activity was found to increase with the decrease in molecular weight and increase in DDA. The encapsulation of COS molecules in HMWNC was found to provide with a facile way of enhancement in the antioxidant activity of COS.