Supercritical CO2 extraction and pre-column derivatization of polysaccharides from Artemisia sphaerocephala Krasch. seeds via gas chromatography

Abstract

Optimal process conditions for supercritical CO2 extraction of polysaccharides from Artemisia sphaerocephala Krasch. seeds and their monosaccharides were analyzed to provide a theoretical basis for identification and development. Single-factor experiments and orthogonal designs were performed to determine the effects of extraction conditions on polysaccharide yields. The polysaccharides were fractionated through ion-exchange chromatography, and were shown to be homogeneous via high-performance size-exclusion chromatography (HPSEC). The resultant polysaccharide samples were hydrolyzed with trifluoroacetic acid, and then acetylated and analyzed for monosaccharide composition by gas chromatography. The optimum extraction parameters were established with extraction pressure of 45MPa, extraction temperature of 45°C, flow rate of CO2 at 20L/h, extraction time of 2h, separation pressure of 10MPa, and separation temperature of 56°C. The corresponding A. sphaerocephala Krasch. seeds polysaccharides (ASKR) yield was 18.59% (w/w). The polysaccharide contained mannose, rhamnose, galactose, glucose, arabinose, xylose, and fucose. The predominant monosaccharides in ASKR were glucose (38.48mg/g) and xylose (16.2mg/g). The average molecular weight of ASKR was 551.3±11.2kDa, and its radius of gyration was 22.6±0.5nm based on HPSEC–MALLS–RI system.