Molecular characteristics of sulfated polysaccharides from Monostroma nitidum and their in vitro anticancer and immunomodulatory activities

Abstract

We investigated water-soluble sulfated polysaccharides isolated from Monostroma nitidum using ion-exchange chromatography to determine their molecular characteristics and biological activities. The crude and fractionated polysaccharides (F(1), F(2), and F(3)) consisted mostly of carbohydrates (58.3-91.9%), uronic acids (0-21.8%) and sulfates (1.8-17.7%) as well as varying amounts of proteins (1.6-9.4%). Their monosaccharide levels were significantly different including rhamnose (0-95.7%) and glucose (0-98.6%) content with small amounts of xylose (0.8-4.3%). These polysaccharides contained one or two subfractions with average molecular weights (M(w)) ranging from 94.4 to 1387×10(3) g/mol. The in vitro inhibitory activity (≤75%) of the polysaccharides on a human cancer cell line (AGS) suggested that the polysaccharides had direct cytotoxic effects on the cancer cells. In addition, these hetero-polysaccharides (from the crude and F(1) and F(2) fractions) stimulated a macrophage cell line, Raw 264.7 cells, inducing considerable NO and PGE(2), production, which suggested that they could be strong immunomodulators.