Molecular weight and monosaccharide composition of Astragalus polysaccharides

Two polysaccharides (APS-I and APS-II) were isolated from the water extract of Radix Astragali and purified through ethanol precipitation, deproteination and by ion-exchange and gel-filtration chromatography. Their molecular weight was determined using high performance liquid chromatography and gel permeation chromatography (HPLC-GPC) and their monosaccharide composition was analyzed by TLC and HPLC methods, using a refractive index detector (RID) and an NH(2) column. It was shown that APS-I consisted of arabinose and glucose and APS-II consisted of rhamnose, arabinose and glucose, in a molar ratio of 1:3.45 and 1:6.25:17.86, respectively. The molecular weights (Mw) of APS-I and APS-II were 1,699,100 Da and 1,197,600 Da, respectively.