分步醇沉对玛咖多糖单糖组成及抗氧化活性的影响

Effect of Step Alcohol Precipitation on Compositions and Antioxidant Activity of Maca Polysaccharide

目的:分析分步醇沉所得玛咖多糖的单糖组成,并对各部分玛咖多糖的抗氧化能力进行研究。方法:采用水提醇沉法得到玛咖粗多糖,通过分步醇沉对玛咖粗多糖进行分离、纯化;采用气相色谱分析法对各玛咖多糖的单糖组成进行分析;最后采用三氯乙酸法和清除DPPH自由基的方法考察各部分玛咖多糖的抗氧化能力。结果:分步醇沉随乙醇浓度增加依次得到0~40%乙醇多糖部分,40%~50%乙醇多糖部分,50%~60%乙醇多糖部分,60%~70%乙醇多糖部分及70%~80%乙醇多糖部分,依次命名为MP1,MP2,MP3,MP4和MP5;其中收率最大的为MP1,纯度最高的为MP4,分别为0.856%和68.5%;经气相色谱技术分析发现不同体积分数乙醇所得玛咖多糖的单糖组成种类及比例不同;抗氧化能力试验结果表明各部分玛咖多糖的抗氧化能力存在显著性差异,其中抗氧化能力最强的为MP5,MP4抗氧化能力次之,抗氧化能力最弱的为MP1。结论:分步醇沉所得各部分玛咖多糖的抗氧化能力有较大差异,玛咖多糖的抗氧化活性与其单糖组成的种类、比例及其空间构象密切相关,分步醇沉对分离纯化玛咖多糖具有重要意义,为玛咖多糖进一步分离纯化、结构组成和药理研究提供可靠的参考依据。

Objective： To analyze the compositions of polysaccharides in Maca obtained by step alcohol precipitation,and study their antioxidant capacity respectively. Method： The crude Maca polysaccharides were obtained by water extraction and alcohol precipitation method, then separated and purified by step alcohol precipitation. Gas chromatography（ GC） was used to analyze the monosaccharide compositions of Maca polysaccharides. Finally,their antioxidant capacity was studied by trichloroacetic acid method and DPPH free radical scavenging method. Result： 0-40% Ethanol polysaccharide,40%-50% ethanol polysaccharide,50%-60% ethanol polysaccharide,60%-70% ethanol polysaccharide and 70%-80% ethanol polysaccharide were obtained as ethanol concentration was increased by fractional precipitation,and they were named as MP1,MP2,MP3,MP4 and MP5 respectively. Among them,MP1 had the highest yield（ 0. 856%） and MP4 had the highest purity（ 68. 5%）. Gas chromatography results showed that the compositions of Maca polysaccharides including the type and ratio of monosaccharides were different under different ethanol concentrations. Antioxidant capacity test results showed that the antioxidant capabilities of different polysaccharide fractions were obviously different,among which MP5 had the strongest antioxidant capacity,followed by MP4,and MP1 had the weakest antioxidant capacity. Conclusion： There was great difference in antioxidant activity for various Maca polysaccharides fractions,and that was related to the type,proportion and spatial conformation of their monosaccharide compositions. The step alcohol precipitation had important significance for the separation and purification of Maca polysaccharides,and it could provide a reliable reference for the further studies on purification,structure and pharmacology of Maca polysaccharides.