Potential Antioxidant Capacity of Sulfated Polysaccharides from the Edible Marine Brown Seaweed Fucus vesiculosus

Fucus vesiculosus was sequentially extracted with water at 22 °C (fraction 1 (F1)) and 60 °C (F2), and with 0.1 M HCl (F3) and 2 M KOH (F4) at 37 °C. Soluble fractions (42.3% yield) were composed of neutral sugars (18.9−48 g/100 g), uronic acids (8.8−52.8 g/100 g), sulfate (2.4−11.5 g/100 g), small amounts of protein (<1−6.1 g/100 g), and nondialyzable polyphenols (0.1−2.7 g/100 g). The main neutral sugars were fucose, glucose, galactose, and xylose. Infrared (IR) spectra of the fractions showed absorption bands at 820−850 and 1225−1250 cm-1 for sulfate. F1, F2, and F4 also exhibited an absorption band at 1425 cm-1, due to uronic acids, and their IR spectra resembled that of alginate. F3 had an IR spectrum similar to that of fucoidan with an average molecular weight of 1.6 × 106 Da, calculated by molecular exclusion high-performance liquid chromatography. The presence of fucose in this polysaccharide was confirmed by 1H NMR spectroscopy. This fraction showed the highest potential to be antioxidant by the ferric reducing antioxidant power (FRAP) assay, followed by the alkali- and water-soluble fractions. Sulfated polysaccharides from edible seaweeds potentially could be used as natural antioxidants by the food industry. Keywords: Edible seaweed; sulfated polysaccharide; antioxidant capacity; ferric reducing ability; Fucus vesiculosus