Extraction, fractionation and physicochemical characterization of water-soluble polysaccharides from Artemisia sphaerocephala Krasch seed

摘要

The extraction and fractionation methods as well as the physicochemical properties of Artemisia sphaerocephala Krasch polysaccharide (ASKP) were studied. ASKP was extracted from the outer layer of the seeds with high ratio of hot water to seeds (400:1, v/w). The yield of water-soluble ASKP was 13.6% (w/w). High performance size exclusion chromatography (HPSEC) results indicated that ASKP had two components with different molecular weights. The high molecular weight (Mw, 551.3 KDa) fraction 60P was separated from the low molecular weight fraction 60S (Mw, 38.7 KDa) by precipitation in 60% (w/v) ammonium sulfate salt solution. Steady flow rheological tests revealed that the apparent viscosity of 1.5% (w/v) ASKP decreased logarithmically with the increasing temperature. Small strain oscillation tests suggested that 4% (w/v) 60P solution was a typical viscous fluid. ASKP was composed of 66.9% (w/w) neutral sugar and 15.8% (w/w) uronic acid; 60P comprised of 55.4% (w/w) neutral sugar and 25.8% (w/w) uronic acid, while in 60S, the percentage of neutral sugar and uronic acid were 87.1% and 10.4%, respectively. Relative monosaccharide composition analysis showed that 60S was composed of 38.3% glucose, 28.1% mannose, 24.2% galactose and 9.4% arabinose, while the 60P fraction contained 80.5% xylose, 10.9% arabinose, 5.0% glucose, 2.3% galactose and 1.2% rhamnose. 60S exhibited the highest surface activity compared to ASKP, 60P, ASKPE (ASKP with protein removed) and 60PE (60P with protein removed) although no protein was detected in this fraction.