Purification, physico-chemical properties and antioxidant activity of polysaccharides from Sargassum fusiforme by hydrogen peroxide/ascorbic acid-assisted extraction

The biological activities of Sargassum fusiforme polysaccharides (SFP) were affected significantly by the extraction method. In order to screen the optimum extraction technology for SFP with high yield and biological activities, six extraction methods, including hot water extraction (HWE), acid-assisted extraction (ACAE), alkali-assisted extraction (ALAE), ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) and hydrogen peroxide/ascorbic acid-assisted extraction (HAE) were compared for the preparation of SFP. Based on the yield and in vitro antioxidant activity of the crude polysaccharides obtained by the six extraction methods, HAE was selected for the extraction of SFP. The SFP prepared by HAE (H-SFP) was purified by cellulose DEAE-52 ion-exchange chromatography, obtaining two purified fractions, namely H-SFP3 and H-SFP5. The analyses of their chemical composition, physico-chemical properties and the antioxidant capacity were performed. It was found that the crude SFP and the purified fractions possessed considerable ability to scavenge DPPH, hydroxyl and ABTS•+ radicals. These polysaccharide fractions were also found to effectively reduce the reactive oxygen species (ROS) level and increase the superoxide dismutase (SOD) activity in H2O2-induced oxidative stress RAW264.7 cells. The SFP prepared by the HAE has the potential as a natural non-toxic antioxidant and can be used as an ingredient in functional foods.