The isolation and antioxidant activity of polysaccharides from the marine microalgae Isochrysis galbana

Three polysaccharides, IPSI-A, IPSI-B and IPSII, were successfully isolated from the marine microalgae Isochrysis galbana through a combination of anion-exchange column chromatography and repeated gel chromatography. These three polysaccharides were demonstrated to have moderate scavenging activities against superoxide and hydroxyl radicals and moderate reductive power in a concentration-dependent manner. The IPSII demonstrated more effective antioxidant activities than IPSI-A and IPSI-B. IPSII had a molecular weight of 15.934 kDa belonging to a β-type heteropolysaccharide with a pyran group and primarily contained mannose with variable amounts of glucose, galactose and rhamnose based on an analysis of infrared spectroscopy (IR), electrospray ionization-mass spectrometry (ESI-MS) and (1)H nuclear magnetic resonance ((1)H NMR).