CHARACTERIZATION AND THERMAL-BEHAVIOR OF 6 SULFATED POLYSACCHARIDES FROM SEAWEEDS

The composition of water soluble polysaccharides from Halymenia ceylanica, Grateloupia filicina, Pterocladia capillacea, Ulva arasakii, Helminthocladia australis and Liagoropsis schramni were analyzed by high performance anion exchange chromatography. The IR and C-13-NMR spectra of these polysaccharides were also investigated. The Pterocladia capillacea agar was a regular, alternating and nearly 'absolute' structure. The G. filicina polysaccharide possessed the 'inter mediate' structure between agar and carrageenan. And H. ceylanica was not well resolved because of its high heterogeneity. In a diluted salt solution the three Rhodophytaceae and the two Helminthocladiaceae polysaccharide molecules showed Gaussian coil behavior with different properties of the polymer-solvent pairs, while Ulvaceae polysaccharide exhibited very different behavior. The thermal behaviors of the polysaccharides were examined by DSC. The thermogram of Pterocladia polysaccharide gel showed three melting-transition endotherms at 40. 75 and 95 degrees C, which might be attributed to the double helix-coil conformation change, the melting of junction zone and the disentangling of the tightest cross-links respectively. There were two endotherms detected on the thermograms of Grateloupia (20-40 and 70 degrees C) and Halymenia (25-50 and 80 degrees C) polysaccharides corresponded to the conformation change and to the aggregation of the random coils. The similar viscometric and thermal behaviors among the polysaccharides in the same family were observed, which could result from their acidic groups, structures and/or conformations, and were useful for the algal taxonomy and applications.