多花黄精多糖的分级提取及结构初步分析

Sequential Extraction and Structural Analysis of Polysaccharides from Polygonatum cyrtonema Hua

本文研究了多花黄精多糖的分级提取及化学结构,为进一步开发利用提供理论依据。多花黄精样品粉碎经石油醚脱脂后,经用热水和不同浓度的NaOH溶液分级提取、乙醇沉淀得到多花黄精多糖(Polygonatum cyrtonema Hua polysaccharides)PCP1、PCP2、PCP3、PCP4和PCP5等五个样品,采用糖组成分析、红外光谱分析、分子量及其分布、核磁波谱分析及热稳定性分析的方法分析其理化性质及结构特征。结果表明,五个样品都含有一定量的阿拉伯糖、半乳糖、葡萄糖、甘露糖和半乳糖醛酸,以及少量的木糖和葡萄糖醛酸,但是水提和进一步碱提的多糖样品在单糖相对含量上呈现出了显著的差异;红外光谱结果显示多花黄精多糖具有明显的糖类物质特征吸收峰且是含有吡喃环的酸性多糖;高效凝胶色谱法(HPGPC)测得PCP1、PCP2、PCP3、PCP4和PCP5等五个样品的重均分子量分别为2090 Da、38600 Da、42600 Da、34300 Da和24100 Da;与水提的样品相比,进一步碱提得到的样品分散度高,分子链长短分布不均匀,热稳定性较差;提取时碱液浓度越高,热稳定性越差;13C NMR进一步表明PCP1异头碳构型主要是β型,有少量α型,含有六种糖残基,而进一步碱提得到的PCP3和PCP5的异头碳构型为α型,PCP3含有四种糖残基,PCP5含有两种糖残基。

To provide the theoretical foundation for further development and utilization of Polygonatum cyrtonema Hua, the sequential extraction and structural composition of P. cyrtonema polysaccharides （PCP） were studied. After removal of resin under petroleum ether reflux, crude polysaccharides were extracted from P. cyrtonema by water and different coneentrations of alkaline solution extraction, and alcohol precipitation. Five samples （ PCP1,PCP2,PCP3, PCP4 and PCP5 ） were successfully obtained. Their chemical structures and physical properties were characterized by monosaeeharide analysis, Fourier-transform infrared spectroscopy （ FT-IR ）, molecular weight determination, NMR spectroscopy and thermal analysis. Monosaccharide analysis indicated that the five polysaecharides basically all contained arabinose, galactose, glucose, mannose, xylose, glucuronic acid and galaeturonic acid, but the relative amount of each monosaeeharide were different. The FT-IR spectra revealed that the structure of PCP had the typical characteristics of carbohydrate polymer with pyranoid rings. The average molecular weights （Mw） of the five pelysaeeharides were 2090 Da,38600 Da,42600 Da, 34300 Da and 24100 Da,respectively. Six types of residues of PCP1 were connected by β- and a -glucoside bond. But residues of PCP3 and PCP5 were only connected by ot-glucoside bond. Compared with water extraction sample ,further alkaline solution extraction samples had higher dispersion degree, non-uniform molecular chain distribution and less thermal stability. In addition, it was found that when the concentration of alkaline was higher, the thermal stability was worse. 13 C NMR spectra showed PCP1 anomerie carbon configuration was mainly β type with a small amount of a type, contained six sugar residues. PCP3 and PCP5 anomerie carbon configurations were a type. PCP3 contained four sugar residues and PCP5 contained two sugar residues.