The hydroxyl radical scavenging activity of chitosan, hyaluronan, starch and their O-carboxymethylated derivatives

In order to study the effect of active hydroxyl and amino groups on scavenging activity against hydroxyl radicals of polysaccharides, three kinds of carboxymethylated polysaccharides (carboxymethyl chitosan (O-CM-chitosan), carboxymethyl hyaluronan (CMHA), and carboxymethyl starch (CMS)) were prepared and their antioxidant activities against hydroxyl radicals were assessed, respectively. Results showed that O-CM-chitosan had lower scavenging ability on hydroxyl radicals than chitosan. CMHA and CMS had the same tendency. For the three kinds of polysaccharides, scavenging ability on hydroxyl radicals was found to be in the order of chitosan > HA > starch. The scavenging ability of carboxymethylated polysaccharides had the same order as related to its corresponding polysaccharides at higher concentrations (≧0.8 mg/ml). There were not only hydroxyl groups but also amino or acetamino (CH3CONH–) groups in the molecules of chitosan and HA, but only hydroxyl group for starch. It was suggested that the sequence influence the scavenging activity against hydroxyl radicals might be amino group > acetamide group > hydroxyl group.