Extraction, derivatization and antioxidant activity of cucumber polysaccharide

The aim of this study was to investigate the effects of derivatization on the antioxidant activity of cucumber polysaccharide. Cucumber polysaccharide was extracted with hot water, and then modified by carboxymethylation and sulfation, respectively. The structures of cucumber polysaccharide and its derivatives were characterized by FT-IR and ¹³C NMR. The content and substitution degree of cucumber polysaccharide and its derivatives were determined by UV absorption spectrophotometry. Antioxidant activities of cucumber polysaccharide and its derivatives were determined by hydroxyl radical scavenging ability and iron ion reducing ability. The results showed that the content of cucumber polysaccharide and its derivatives was 20.60%, 44.07% and 31.20% respectively, and the substitution degree of carboxymethylated and sulfated cucumber polysaccharide was 0.18 and 0.65, respectively. Cucumber polysaccharide itself had strong hydroxyl radical scavenging ability (80%) and reducing ability, and it had high antioxidant activity, while the carboxymethylation and sulfation modification of cucumber polysaccharide reduced its antioxidant activity.