Structure Analysis And Anti-fatigue Activity Of A Polysaccharide From Lepidium Meyenii Walp

Lepidium meyenii Walp(Maca)is a kind of medicinal food,which has good edible value and health function,while the polysaccharide composition in maca has the biological activity of antioxidation and antifatigue.Maca powder as raw material by single factor and orthogonal experiment to optimize the extraction process of maca polysaccharide,and the experimental results show that the optimal extraction conditions:water extraction time is 3 h,extraction temperature,80?,material liquid ratio is 1:20,maca polysaccharide alcohol concentration of 80%ethanol.The raw polysaccharide of Maca was through hot water method leached,and centrifugation was taken to remove the precipitate,ethanol precipitate,except starch,except protein,vacuum freeze-dried to obtain water-soluble maca polysaccharide,which was purified by Sephadex G-200 to obtain maca polysaccharide.The content of polysaccharide was examined to be 92.44%with phenol-sulfuric acid method.Its average molecular weight was estimated to be 2.213×106 Da by High Performance Gel Permeation Chromatography(HPGPC).Monosaccharide analysis showed that the polysaccharide was composed of arabinose,mannose,glucose and galactose with the molar ratio of 2.134:1:2.78:2.82.After Smith degradation,methylation,infrared spectroscopy and NMR,the primary structure of the polysaccharide was identified.The backbone of the polysaccharide was composed of?4)-?-D-Galp-(1?and?4)-?-D-Galp-(1?,while the branches were comprised of?6)-?-D-Glup-(1?,?5)-?-D-Araf-(1?,?3,6)-?-D-Manp-(1?,?3)-?-D-Galp-(1?,and ?-D-Glup-(1?.Its morphological characteristics were identified by Congo red experiments and scanning electron microscopy(SEM)analysis.The results show that Maca polysaccharide does not have a triple-helical conformation in solution;its shape a smooth block structure.The anti-fatigue effect of the polysaccharide was evaluated using exhaustive swimming test and biochemical indexes.The results indicated that high doses of maca polysaccharide can significantly improve the exhaustion of mice swimming time on mice,and biochemical experiments shows that maca polysaccharide can significantly lower the serum urea nitrogen content in mice,improve the glycogen content in mice,increase the enzyme activity of lactic dehydrogenase in mice,so as to reduce the accumulation of lactic acid in mice.