Abstract

The water soluble protein-sulfated fucan (PSF) complex isolated from the body wall of Stichopus japonicus was fractionated using an anion-exchange chromatography to obtain four purified fractions (F₁, F₂, F₃, and F₄) and to investigate their structural characteristics and immuno-enhancing activities. The crude PSF and fractions mostly consisted of neutral sugars, proteins and sulfates in various proportions. Fucose was their major monosaccharide unit with small portion of mannose, glucose and galactose. The molecular weight (M_w) of the crude PSF and fractions ranged from 323.6 × 10³ to 3630.0 × 10³ g/mol. The crude PSF, F₂, and F₃ were potent stimulator of RAW264.7 cells inducing marked nitric oxide (NO) and cytokines production. The glycosidic linkage of polysaccharides was evaluated using GC–MS and confirmed by 2D-NMR. The main backbone of highly immunostimulating F₃ fraction was (1 → 3)-α-l-linked fucosyl residue with sulfation at C-2 and/or C-4.