Organic derivatives of algal polysaccharides

A survey of organic derivatives of commercially important red seaweed polys accharides is presented. The most important applications of soluble polysac charides extracted from seaweeds utilize their ability to modify the proper ties of aqueous solutions. The presence of natural substituents and synthet ic derivatives have broadened the area of applicability of phycocolloids. T he ability of polysaccharides, such as agarose to form hydrophilic supports of well defined dimensions has been exploited for the purification of biol ogical molecules. By appropiate modification of the polysaccharide matrices , derivatives useful in the field of medicine, biology and, biotechnology h ave been developed: Selective chemical modifications may facilitate the pre paration of derivatives and conjugates with novel applications. Treatment o f polysaccharides with bromine and periodate may introduce ketone or aldehy de functions, respectively. Neutral polysaccharides, such as agarose and xy lan, were oxidized with aqueous bromine and then coupled with amines to giv e conjugates with potential biological applications. On the other hand, for mation of Schiff bases afforded derivatives with metal chelating properties . One of the recent seaweed polysaccharide manipulation involves conjugates with protein carriers, which can be artificial immunogen. Alginic acid, fr om Lessonia trabeculata and its homoguluronic enriched fraction by reaction with caprolactam gave amido derivatives which formed covalent bonding with tetanic toroid protein. Introduction of keto group in alginic acid, follow ed by selective acetylation gave analogs of Salmonella typhi capsular polys accharide. These analogs can be linked to carrier proteins by reductive ami nation.