Isolation and analysis of a novel acidic polysaccharide with glucokinase-stimulating activity from coarse green tea

Water-soluble polysaccharides from coarse green tea were separated by anion-exchange chromatography into five fractions (fraction A [FA], fraction B, fraction C [FC], fraction D and fraction E). Two of these fractions, FA and FC, contained significant glucokinase-stimulating activity (P < 0.05). The major component, FC, showed the most activity, and thus, was further purified by gel filtration chromatography, thereby obtaining fraction C-1 (FC-1) and fraction C-2 (FC-2). The biological activity of the two fractions was investigated, and FC-1 displayed higher glucokinase-stimulating activity (P < 0.01). Chemical tests combined with IR and UV spectroscopy revealed that FC-1 is an acidic polysaccharide without conjugation to protein. Sugars of FC-1 are composed of rhamnose, arabinose, mannose, glucose and galactose in the ratio of 12.57:22.95:4.4:39.34:20.77. Uronic acid analysis by ion chromatography showed that FC-1 contains 8% galacturonic acid, and its molecular weight was estimated to be approximately 6 x 10(4) using a Sephacryl S200 column. These results are different from the observations previously reported, therefore suggesting that FC-1 is a novel polysaccharide.