Extraction and Characterization of Fucoidan from Fucus vesiculosus

Fucoidan with an average Mw of 735 kDa was provided by MMBI KSC RAS, Murmansk, Russia. Fucoidan was extracted from F. vesiculosus by ultrasound-assisted extraction [72 (link)] according to the procedure described previously [18 (link)]. The yield of fucoidan was 4.9% by mass. Fucoidan contained 79.5% of neutral carbohydrates, 27.0% of sulfate residues, and 0.7% of uronic acid. Carbohydrates were represented by fucose (73.5 mol%), glucose (11.8 mol%), galactose (3.7 mol%), xylose (6.6 mol%), mannose (0.2 mol%), and arabinose (0.2 mol%). The molar ratio of fucose, glucose, galactose, xylose, mannose, and arabinose was 1.0:0.16:0.05:0.09:0.03:0.03, respectively, as evidenced by high performance liquid chromatography (HPLC) [18 (link)]. According to the literature data, fucoidans from Fucus spp. are represented mainly by (1→3)- and (1→4)-linked α-l-fucopyranose residues [3 (link),36 (link)]. Electrospray ionization mass spectrometry evidenced that sulfate groups are attached mostly at C-2 and sometimes at C-4 of sugar residues in fucoidans from brown seaweeds [73 (link)].
The concentration of total polyphenols was determined with Folin–Ciocalteu reagent as described previously [74 (link)]. Phloroglucinol (Sigma, St. Louis, MO, USA) was used as reference. The total polyphenol content was 4.7 ± 0.5 mg PGEq g⁻¹ (milligram of Phloroglucinol equivalent PGEq per 1 g fucoidan).