Preparation And The Biological Activities Of Phthaloyl κ-Carrageenan

Carrageenans are a family of sulfated polysaccharides prepared by alkaline extraction (and modification) from red seaweed and the first natural sulfated polysaccharides found to have anti-human immunodeficiency virus (HIV) activity. Molecule weight of the natural carrageenans is so large that it is difficult to penetrate biofilm. So The application of carrageenans to clinical is restricted. Depolymerization and O-acylation of carrageenans are favor of improving their bioactivity. In this study, carrageenan polysaccharide was degraded by mild acidic hydrolysis and the oligosaccharide and its acetylated derivative was prepared and their structures were elucidated and their bioactivities were investigated. The main contents are summarized as follows.1. Low-molecular-weightκ-carrageenan (LMW-KC) with the weight-average molecular weight of 25450 and number-average molecular weight of 11132 was achieved by degradingκ-carrageenan (KC) with 0.1 mol/L sulfuric acid for 1h. Compared withκ-carrageenan, the disaccharide repeating units of LMW-KC were not destroyed, and the content of S was not changed.2. O-phthaloyl derivative of LMW-KC was synthesized. The acylation of LMW-KC was performed by use of tetrabutylammonium (TBA) salt of the anionic polysaccharide fragments, phthalic anhydride, 4-dimethylaminopyridine and tributylamine under homogeneous conditions in N,N-dimethylformamide at 60℃for12h. Investigation of FT-IR spectrum of the phthaloylated LMW-KC showed that a ester derivative with phthaloyl group was formed and the phthaloylated LMW-KC successfully formed when LMW-KC reacted with phthalic anhydrade.3. Agglutinative activity of O-phthaloyl derivative of LMW-KC on three types of erythrocyte were investigated. The results show that agglutinative function of derivative was obviously higher than LMW-KC.The scope of agglutinative activity of derivative and LMW-KC were 3.9～8mg/L and 125～1000 mg/L, respectively, which were nearly sixteen times or two hundred fifty times as high as LMW-KC at the same condition.4. Scavenging effect of O- phthaloyl derivative of LMW-KC on superoxide anion and inhibiting effect of them on hemolysis were tested. The results show that ability of scavenging superoxide anion and inhibiting hemolysis of derivative was clearly higher than LMW-KC,the high scavenging rate were 52% and 65 %,respectively.