Ultrasound-assisted extraction of polysaccharides from brown alga (Sargassum angustifolium): structural characterization, antioxidant, and antitumor activities

In this study, crude polysaccharide of Sargassum angustifolium (PSA) was extracted with an extraction efficiency of 7.14% and a molecular weight of 1831.55 kDa. Then two fractions PSA-1 and PSA-2 with yields of 38.12% and 61.07% and molecular weights of 809.2 and 644.1 kDa were obtained by a DEAE column. Based on the results, fucose (40.41%), glucose (19.30%) and galactose (27.13%) were identified as the dominant monosaccharides in polysaccharides. The IC50 value of DPPH free radical scavenging by PSA, PSA-1 and PSA-2 was 0.32, 0.24 and 0.19 mg/mL, respectively. Also, the IC50 value of ABTS radical scavenging by PSA, PSA-1 and PSA-2 was estimated at about 0.24, 0.17 and 0.14 mg/mL, respectively. According to the results, Fraction PSA-2 had the highest antioxidant activity. In this study, the ability of all fractions to inhibit Hela cancer cells was determined, and the most significant effect was observed by fraction PSA-2. The inhibition rate of HeLa cells by PSA and PSA-1 and PSA-2, at a concentration of 0.4 mg/mL was about 40.56% and 51.70% and 70.81%, respectively. Therefore, S. angustifolium polysaccharide, especially fraction PSA-2, can be introduced as a natural compound with anticancer and antioxidant activity for food and pharmaceutical applications.