选用蛹虫草粗多糖进行分离纯化,借助二乙氨基乙基纤维素52(DEAE-52)柱层析得到虫草中性多糖(Cordyceps militaris polysaccharide, CMP)。采用紫外可见光谱(UV-visible)和傅里叶变换红外光谱(fourier transform infrared spectroscopy, FT-IR)表征CMP,同时选用气质联用技术(GC-MS)测定单糖组成,并采用多角度激光光散射凝胶渗透色谱和示差联用(gel permeation chromatographymulti-angle laser light scattering-reflective index, GPC-MALLS-RI)测定CMP重均分子质量(MW)和均方根旋转半径(Rg),同时分析CMP在溶液中的构象。此外,对粗多糖和CMP的抗氧化活性进行比较。结果表明:经DEAE-52水洗的中性多糖CMP质量分数为76.63%,比粗多糖(44.95%)纯度提高70.48%;在260 nm和280 nm处均无明显紫外吸收;FT-IR说明CMP为α-构型多糖;其单糖组成为甘露糖、葡萄糖和半乳糖,摩尔比为1∶3.90∶1.51;MW和Rg分别为2.432×107 g/mol,31 nm;CMP在溶液状态下为高枝化度结构。1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)和2,2′-联氨-双-(3-乙基-苯并噻唑啉-6-磺酸)二铵盐(2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid),ABTS)自由基清除实验表明,CMP具有明显的抗氧化活性,且自由基清除率高于粗多糖。
关键词：
蛹虫草; 多糖; 单糖; 分子量; 构型; 抗氧化
A neutral Cordyceps militaris polysaccharide (CMP) from crude Cordyceps militaris polysaccharides was purified by using dicthylaminoethyl 52(DEAE-52)column chromatography. The CMP was characterized by ultraviolet-visible (UV-visible) and fourier transforming infrared spectroscopy (FT-IR). Gas chromatography-mass spectrometry (GC-MS) was applied to analyze the composition of monosaccharides. The weight-average molecular weight (MW) and the radii of gyration (Rg) of CMP were measured by multi-angle laser light scattering (MALLS), gel permeation chromatography (GPC) combined with reflective index detector (GPC-MALLS-RI). The chain conformation of CMP in solution was clarified at the same time. Additionally, the antioxidant activities of crude polysaccharides and CMP were compared. The results showed that CMP purified by DEAE-52 column had higher purity (mass fraction=76.63%), which was approximately 70.48% higher than that of crude polysaccharides (44.95%); The UV-visible spectrum showed that CMP had no significant absorption peaks at 260 nm and 280 nm. FT-IR revealed that CMP was an α-type polysaccharide. The monosaccharide compositions of CMP were mannose, glucose and galactose, with a molar ratio 1∶3.90∶1.51. The MW and Rg of CMP were 2.432×107 g/mol and 31 nm, respectively. Moreover, CMP exhibited a highly branched structure in solution. Furthermore, CMP had stronger DPPH and ABTS radical scavenging capacities than crude polysaccharides, which indicated that CMP possessed significant antioxidant activities.
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