Extraction, Purification And Property Of Neutral Polysaccharide In Garlic (Allium Sativum L.)

Garlic (Allium Sativum L.), which belongs to the lily family has extensive pharmaceutical function, and stores carbohydrates in cloves making up 75% of the dry matter. The crude polysaccharide was isolated from defatted garlic powder with hot water. Based on the single factor experiment, the optimum parameters and scopes are ensured by the method of orthogonal design and the regression equation is established. Neutral polysaccharide B2 was purified by successive procedures, including precipitated by fractional precipitation with ethanol, deproteinized by Sevag method, dialysised with distilled water and further separated by DEAE-cellulose chromatography column. The physical and chemical properties of B2 were also studied in this thesis and the results provide foundation for further research and utilization of garlic. The main experiment results were as follows:1.According to the study, the extraction temperature, time and the ratio of material to water were the main factors that affect the extraction rate of polysaccharide. The optimum parameters were as follows: the extraction temperature is 83.57℃, time is 205.48min, the ratio of material to water is 1:6.97 respectively.2.The purification of garlic polysaccharide. The successive procedures were as follows: first, crude polysaccharide liquor was deproteinized partially by adjusting to pH 4.5 and 8.5, secondly, GPS75 was precipitated with 50%~75%(v/v) ethanol, thirdly, B1 was deproteinized by Sevag method and dialysised with distilled water, fourthly, B2 was further purified by DEAE-cellulose column chromatography and collected according to the peak of the elution curve of water. The purity of GPS75 was 60.2%, of B1 was 89.08, and of B2 was 98.26%.3.The properties of B2. Polysaccharide B2 is composed of fructose and galactose with the molar ratio of 51.46:1. The average molecular weight of B2 is estimated to be 7.1×103 Dalton. The data of IR revealed that B2 is chiefly linked by β-glycosidic bonds. B2 dissolves in water and the solubility is 102g(25℃). It also dissolves in solution of pH 3and pH 11. And B2 cannot be hydrolyzed in solution of pH 3. But B2 doesn't dissolve in some organic solvent such as ethanol, aether and acetone. The melting point of B2 is 231.7～232.5℃. B2 responded negatively to Lane and Eynon's Method, iodostarch reaction and dye reaction of Coomassie Brilliant Blue G-250.4.The viscosity character of crude polysaccharide GPS75 accords with Rheology principle of Newton Liquid in low concentration and of Pseudoplastic Liquid in high concentration.5.Average extraction rate of garlic bulbs was 15.05%, of garlic powder originally from Cangshan was 65.00%, of garlic powder originally from Jinxiang was 60.90%.