Effect of ultrasound-assisted extraction on antioxidant properties of water-soluble sulfated polysaccharides from Enteromorpha intestinalis

Effect of different temperature (30 to 90 °C), time (10 to 70 min) and pH (4 to 9) conditions were investigated on the extraction efficiency of polysaccharides from seaweed E. intestinalis. Results showed that the extraction temperature had the highest effect on the enhancement of polysaccharide content. The highest polysaccharide extraction yield was achieved at 90 °C, 30 min and pH 8. Therefore, antioxidant effects of polysaccharides obtained at temperatures 30, 70 and 90 °C, times 10, 30 and 50 min, and pH 4, 7 and 8 with significant yield differences were evaluated. DPPH radical scavenging activity, ferric reducing power and total antioxidant activity were employed in order to evaluate the antioxidant properties of polysaccharides. The maximum DPPH radical scavenging activity was obtained for polysaccharides of 30 °C (73.90%), 30 min (95.08%) and pH 7 (75.61%). The highest reducing power was achieved for polysaccharides of 70 °C (97.49%), 50 min (99.05%) and pH 8 (97.49%). The maximum total antioxidant activity was obtained for polysaccharides of 70 °C (49.97), 10 min (62.32) and pH 7 (59.11 mg ascorbic acid/ g dried seaweed powder?). Overall, findings of current study suggest that the polysaccharides from green seaweed E. intestinalis possess antioxidant capacity and that the use of high temperature, long time and acidic or basic pH in extraction process results in diminishing this antioxidant capacity.