Studies On Isolation, Purification And Physicochemical Property Of Highland Barley

Highland barley {Hordeum Vulgare L var. nudum Hook.fi is a kind of characteristic crops in Tibet region .Considerable attention has been focused on it for its abundant P -glucan. In this paper , β-glucan has been extracted by means of hot water with highland barley bran as raw materials .Based on the single factor experiment , technological parameters of extraction has been defined and the effects of factors on extraction has been described. The feasibility of experiment results has been verified.. A P -glucan was obtained from crude β -glucan by removal of protein . precipitation by ethanol , ammonium sulfate fractionation , dialysis, cellulose column chromatography and Sephadex G-100 column chromatography . The optimized conditions of precipitation by ethanol and column chromatography have been determined. Purity and physicochemical property of A P -glucan has also been determined and analyzed. The results showed as follows.1. The content of P -glucan is highest in highland barley bran (5.78% )。 It indicated that P -glucan was found mainly in aleurone layer of highland barley.2. The effect of pretreatment (drying with high temperature and ethanol refluxing )on extraction of P -glucan was not significant.3. The order of major and secondary factors influencing β-glucan extraction was pH , temperature, time and stock ratio. The optimum extraction conditions were: pH 9, 50℃,time 2h, stock ratio 1:15. and two times of extraction. The yield from barley bran was 6.65%,The purified preparation contained 64.72% P -glucan.4. The purification process of P -glucan was confirmed: removal of protein by adjusting pH. ammonium sulfate fractionation. precipitation by ethanol. β-glucan with 88.7% purity was obtained. Then cellulose column chromatography and Sephadex G-100 column chromatography was used to isolate it and A P -glucan with analogous molecular weight was gained.Its ratios was 0.45%.5 .Monosaccharide of A P -glucan was made of glucose. Molecular weight of sample A was 3.0 × 10⁵ Dal, Sample was composed of glucosyl bond.Sample A was insoluble in ethanol, aether and acetone. Its viscosities was 42 mPa · S. [α ]D²⁰ (H₂O) was -95.3 .They had no color reaction with potassium iodide, which explained that they were non-starch polysaccharide. Their reaction with Fehling reagents ,biuret reagents, ferric chloride reagents, CTAB reagents and their absorption in 280nm were negative. These results showed that they did not contain monosaccharide, protein, polyphenols and nucleic acid and they were neutral, polysaccharide.