Extraction, derivatization and antioxidant activities of onion polysaccharide.

The preparation of purified polysaccharides was described from fresh onions by hot water extraction, protein removal and dialysis treatment. The structure of onion polysaccharide was confirmed by 13C NMR, DEPT, COSY, HSQC and HMBC. In order to study the structure-activity relationship of onion polysaccharide, the derivatives of onion polysaccharide including acetylated onion polysaccharide and phosphoric onion polysaccharide were prepared. On this basis, the antioxidant activities of onion polysaccharide and its derivatives were tested in vitro. The results showed that onion polysaccharides and its derivatives had a good antioxidant activity, and the activity of phosphorylated polysaccharide was similar to that of Vc positive control.