Water-soluble polysaccharides from Ulva intestinalis : Molecular properties, structural elucidation and immunomodulatory activities

Water-soluble sulfated polysaccharides extracted from Ulva intestinalis and fractionated using DEAE Sepharose fast flow column to identify their molecular properties and macrophage cells stimulating activities. Crude and fractions (F 1 and F 2 ) were formed of neutral sugars (58.7–74.7%), sulfates (6.2–24.5%), uronic acids (4.9–5.9%) and proteins (3.2–10.4%). Different levels of sugar constituents including rhamnose (30.1–39.1%), glucose (39.0–48.4%), galactose (0.0–15.8%), xylose (8.5–11.3) and arabinose (0.0–5.1%). The molecular weight ( M w ) of crude and fractionated polysaccharides ranged from 87.1 × 10 3 to 194.1 × 10 3 (g/mol). Crude polysaccharides were not toxic to RAW264.7 cells and fractions induced cell proliferation. Fraction F 1 stimulated RAW264.7 cells to release considerable amounts of nitric oxide, IL-1β, TNF-α, IL-6, IL-10 and IL-12 cytokines. The main backbone of the most immunostimulating polysaccharide (F 1 ) was consisted of mixed linkages of (1 → 2)-linked rhamnose and (1 → 2)-linked glucose residues.