黑小麦麦麸戊聚糖的提取、纯化与组成分析

Extraction,Purification and Composition Analysis of Pentosan from Black-grained Wheat Bran

对黑小麦麦麸戊聚糖进行提取、纯化及组成分析。分别以H2O、Ba（OH）2和Na（OH）2为提取介质，提取水溶性和水不溶性戊聚糖；采用（NH4）2SO4分级沉淀、乙醇分级沉淀、凝胶过滤柱层析等方法纯化戊聚糖粗提物，分析其得率和组成。结果表明：水提组分（WEP）主要由葡萄糖（Glc）、阿拉伯糖（Ara）和木糖（Xyl）组成，是β-葡聚糖（79％）和戊聚糖（21％）的混合物。NaOH碱提组分（AEP—Na）中Ara和Xyl含量相对较高，以戊聚糖为主要组成（71％），还含有29％的β-葡聚糖。Ba（OH）：碱提组分（AEP—Ba）主要由阿拉伯糖（Ara）和木糖（Xyl）组成，舍有较纯的戊聚糖（96％）。WEP经35％饱和（NH4）2S04溶液沉淀后，戊聚糖含量由纯化前的21％提高到35％。AEP—Na经DEAE—Sepharose CL-6B柱层析．分级组分AEP—Nal的单糖组成的物质的量比，即n（Ara）：n（Xyl）：n（Glc）=0．7：1：1．2，其中戊聚糖的n（Ara）／n（Xyl）=0．7。AEP—Ba经不同浓度乙醇沉淀分级组分的戊聚糖主要由Ara和Xyl组成。其n（Ara）／n（Xyl）在0.38～1．02之间，且Ara的取代度随着乙醇浓度的增加而增大。

Pentosan from black-grained wheat bran was isolated, purified and composition was analyzed. Water soluble and water unsoluble crude pentosan were isolated using water, barium hydroxide, sodium hydroxide as extraction medium and were further purified by ammonium sulphate precipitation, stepwise ethanol precipitation, and gel filtration chromatography methods. Yields and compositions of the fractions were analyzed. The results showed that the water solu-ble fraction WEP was composed of glucose, arabinose, and xylose, which was the mixture of β-glucan and pentosan. AEP-Na had a high content of arabinose and xylose, which had the main component of pentosan （71%） and the minor part of β-glucan （29%）. AEP-Ba contained mainly arabinose and xylose, which contain more pure pentosan （96%）. The content of pentosan in WEP was increased from 21% to 35% after ammonium sulphate fractionatlon. AEP1, which fractioneted on DEAE-Sepharose CL-6B chromatography of AEP, has the monosaccharide mol. ratio of n（Ara）：n（Xyl）：n（Glc） =0.7：1：1.2, with the high n （Ara）/n （Xyl） ratio of 0.7. Fractions by ethanol precipitation of AEP-Ba were composed of arabinose and xylose, and the n （Ara）/n （Xyl） ratio changed from 0.38 to 1.02, which incereased as the concentration of ethanol increased.