Study On The Extraction And Purification Of Arabinogalactan From Larix

In this paper, larch sawdust was as raw materials. Extraction, separation, purification, some physicochemical properties, structure and antioxidant activity in vitro of larch arabinogalactan were studied, which lay the foundation for its further development and utilization.To extract arabinogalactan with water extraction and alcohol precipitation techniques was studied. The optimum extraction technology of larch arabinogalactan was established by single factor and orthogonal tests. The optimum extraction technology was as follows: particle size of raw materials of40to60mesh, extracting temperature of70℃, the solid-liquid ratio of1:10, the extracting time of2h for twice. The optimum ethanol precipitation technology was as follows:the concentrated ratio of the extracting liquid of51, adding95%ethanol and making the final concentration of70%and ethanol precipitation time of20h. In that condition, the yield of arabinogalactan was8.40%.The crude polysaccharide was purified using the lime for deproteinization and active carbon for decolorization. The suitable conditions of deproteinization using the lime were as follows:adding calcium hydroxide of0.04%, heating for40min at70℃. In that condition, the rate of deproteinization was up to96.80%. The suitable conditions of decolorization using active carbon were as follows:adding active carbon of1.0%, decolorizing temperature of40℃, decolorizing time of20min. In that condition, the decolored rate was40.10%.The effects of decolorization and deproteinization of ten kinds of resin were studied, and in the final, the polyamide resin was chosen. The suitable conditions of decolorization and deproteimzation using the polyamide resin were as follows:adding the polyamide resin of5.0%, adsorping12h. In that condition, the decolored rate was64.87%, the rate of deproteinization was85.38%, and the loss rate of arabinogalactan was7.97%.Purified polysaccharide was isolated and purified by DEAE-cellulose(OH-) column, and two kinds of polysaccharide were obtained. They were LAG-1eluted by ditilled water and LAG-2eluted by0.05mol/LNaCl solution. LAG-1and LAG-2were isolated and purified by Sephadex G-75gel column, and LAG-la, LAG-1b and LAG-2a were obtained. High performance gel permeation chromatography of LAG-1b was single and symmetrical peaks, which indicated LAG-lb was homogeneous component. The weight average molecular of LAG-1b was21021Da.The results of physicochemical properties showed that LAG-la, LAG-lb and LAG-2a were soluble in cold water, dilute alkali, and their water solution was transparent; They were not soluble in ethanol, acetone and other organic solvents. They didn’t contain reducing sugar, starch, free protein, phenols and other impurities. The gas chromatography showed LAG-la, LAG-lb and LAG-2a were mainly composed of arabinose and galactose.The results of UV spectrum showed that there were no nucleic acid and protein absorption peaks in LAG-la, LAG-1b and LAG-2a. The results of IR spectrum showed that there both were characteristic absorption peaks of polysaccharide and pyran ring in LAG-la, LAG-lb and LAG-2a, and their sugar ring were β-glycosidic linkage. The experimental results of Iodine-potassium iodide showed that LAG-la, LAG-lb and LAG-2a may exist longer side chains and more branching. The experimental results of congo red showed that LAG-la and LAG-lb were both ordered triple-helical structure, and LAG-2a was not triple-helical structure.The results of antioxidant activity in vitro showed that with increasing concentrations of polysaccharide, the reducing power, the capacity of scavenging hydroxyl free radical and DPPH free radical of LAG-1and LAG-2gradulally increased. And at the same concentration, the antioxidant activity of LAG-2was stronger than LAG-1.