Extraction,isolation and structural characterization of polysaccharides from a red alga <Emphasis Type="Italic">Gloiopeltis furcata</Emphasis>

Three kinds of polysaccharides:GFW,GFH and GFA,were sequentially extracted from a red alga Gloiopeltis furcata with 25℃ and 85℃ water,and 60℃ 4% NaOH water solution.Based on the defatted alga,the yields of the polysaccharide were 57.9%,2.5% and 2.6%,respectively.Their monosaccharide compositions,average molecular weights and structural characters were determined by gas chromatography(GC),high performance liquid chromatography(HPLC),fourier transform infrared spectroscopy (FTIR)or 13C-NMR spectroscopy.The results showed that GFW,GFH and GFA were all composed of D-galactose(Gal)and 3,6-anhydro-L-galactose(AnG),and particularly GFA also contained xylose(Xyl).The average molecular weights of GFW,GFH and GFA were 22.6 kD,26.5 kD and 49.8kD,respectively,with the respective sulfate content 31.2%,25.1% and 22.7%.The data of FTIR and 13C-NMR confirmed the sulfate ester location at C6 ofgalactose.It is concluded that all the three polysaccharides extracted from Gloiopeltisfurcata were sulfated galactans,two being sulfated-agarose,and one being xylose-containing sulfated galactan.