Biological properties of ulvan, a new source of green seaweed sulfated polysaccharides, on cultured normal and cancerous colonic epithelial tells

Ulvans (from Ulva lactuca) constitute a dietary fiber structurally similar to the mammalian glycosaminoglycans but with unexplored biological or cytot oxic activities. From native low-viscosity preparations containing 33.5 mol ar % and 18.4 molar % of sulfate residues and uronic acid residues, respect ively, we derived desulfated, reduced and desulfated-reduced polysaccharide s with respectively 5.2, 2.9, and 4.5-4.9 molar % of sulfate residues and u ronic acid residues. The effects of these preparations were examined on the adhesion, proliferation and differentiation of normal or tumoral colonic e pithelial cells cultured in conventional (0.3-0.8 x 10(6) cells/ml) or rota ting bioreactor (3-8 x 10(6) cells/ml) culture conditions. in conventional culture conditions, ulvan modified the adhesion phase and the proliferation of normal colonic cells and undifferentiated HT-29 cells according to thei r molecular weights and to the relative molar proportion of sulfate residue s. From the native polysaccharides, we have screened sulfated ulvans (MW < 5,000) which inhibited the Caco-2 cell proliferation/differentiation progra m by inducing a low cell reactivity to Ulex europeaus-1 lectins in defined (p < 0.001) or serum-supplemented media (p < 0.01) but were inactive on nor mal colonocytes. In conclusion, this dietary fiber could be a source of oli gosaccharides with a bioactivity, a cytotoxicity or a cytostaticity targete d to normal or cancerous epithelial cells.