Purification And Structural Analysis Of The Polysaccharide From Scutellaria Barbata

Scutellaria barbata D.Don is also known as toothbrush grass,it belongs to Labiatae Scutellaria.It is mainly distributed in Argentina,China and Uruguay.As the main active substance of Scutellaria barbata D.Don,polysaccharides have many important biological activities,such as enhancing the anti-tumor ability and increasing the potential anti-aging effects of body,and improving the immunity of body.At present,there are few studies on systematic separation and purification and reports on structural analysis of the polysaccharides of Scutellaria barbata D.Don.In order to deeply understand the composition and structure of the polysaccharides of Scutellaria barbata D.Don,we designed the research content of this topic.The specific results are as follows:The water-soluble polysaccharides,which were referred to as WSBP,were extracted from Scutellaria barbata D.Don by boiling water extraction and ethanol precipitation,the yield was 8.9%,WSBP contained 60.7% total carbohydrates,14.9% uronic acid,35.2% ash and 1.9% protein.Sugar composition analysis indicated that WSBP were mainly composed of glucuronic acid,mannose,galacturonic acid,glucose and galactose,WSBP also contained a small amount of rhamnose and arabinose.WSBP were separated on a DEAE-Cellulose column into two fractions: a Scutellaria barbata D.Don neutral fraction(WSBP-N)by water elution and a Scutellaria barbata D.Don acidic fraction(WSBP-A)by 0.5 M NaCl elution,the yields of them were 50.8% and 20.2% respectively.The acidic fraction was further fractionated by de-esterification enzymolysis,ion-exchange column chromatography and gel column chromatography to obtain three fractions WSBP-A-UD2 a,WSBP-A-UD2 b and WSBP-A-UD3.By means of molecular weight determination?sugar composition analysis?FT-IR?acid hydrolysis?ESI-MS analysis?methylation analysis and NMR analysis,WSBP-A-UD2 b was composed of RG-II domain with molecular weight of 5.1 KDa,the side chain B in it was nonasaccharides with 0 to 1 acetyl group,the side chain A in it was octasaccharides with 0 to 1 methyl group,the structure of one fucose replaced by one galactose also existed.The molecular weight of WSBP-A-UD2 a was 578.1 KDa,the molecular weight of WSBP-A-UD3 was 342.8 KDa,the backbones of WSBP-A-UD2 a and WSBP-A-UD3 were both composed of the linkage forms of 1,2-Man and 1,4-GlcA,the backbones have high degree of branching,with a side chain attached to the O-3 position of Man,the side chain was composed of terminal galactose.There was also a small amount of galactose in WSBP-A-UD3 attached to the side chain in the linkage form of ?-1,6-Galp.