Structural characterization and antioxidant activity of polysaccharides extracted from Chinese yam by a cellulase-assisted method

Cellulase-assisted extraction of Chinese yam polysaccharides was investigated in the present study. The optimized method generated a polysaccharide yield of 10.6 % (w/w) from Chinese yam in 80 min using 8000 U/g of cellulose. Three polysaccharide fractions (CYP1, CYP2 and CYP3) were purified by Cellulose DEAE-52, and their structures and antioxidant activities were determined. There were five monosaccharides, namely arabinose, galactose, glucose, mannose, and galacturonic acid, in both CYP2 and CYP3, but in CYP1, there were only four monosaccharides, as galacturonic acid was missing. CYP1 and CPY2 were heteropolysaccharides; CYP3 was a homogeneous polysaccharide. Moreover, CYP3 showed the strongest antioxidant activity. Thus, methylation and NMR analysis were further applied to elucidate the detailed structure of CYP3. The backbone of CYP3 is composed of 1,2,4-linked-D- Glcp and 1,3,6-linked-D- Glcp. Bioactivity evaluation showed that CYP3 exhibited significant antioxidant activity in vitro, supporting the potential application of CYP3 as an antioxidant in food processing, pharmaceuticals and other applications.