Water-soluble anionic macromolecules isolated from Codium fragile and fractionated using ion-exchange chromatography were investigated to determine their molecular characteristics and immunostimulating activity. The crude molecules and fractions (F1, F2, and F3) consisted mostly of carbohydrates (44.1-80.5%), sulfates (3.2-22.2%) and proteins (3.0-15.7%) with small amounts of uronic acids (1.1-4.2%), and included different levels of mannose (91.3-18.7%), glucose (62.7-8.6%) and galactose (37.5-59.5%). These molecules contained one or two subfractions with molecular weights (Mw) ranging from 148×10(3) to 4879×10(3)g/mol. The crude, F1 and F2 stimulated RAW264.7 cells to produce considerable amounts of pro-inflammatory mediator nitric oxide (NO) and cytokines. The treatment of sample molecules facilitated the degradation of Iκ-B and phosphorylation of MAPK in RAW264.7 cells, suggesting that they might stimulate RAW264.7 cells through the activation of NF-κB and MAPK pathway. Proteins in fraction F2 were essential to possess its bioactivity and its main backbone was composed of mixed linkages of (1→3)-α and β-d-mannan.
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