Extraction,Purification,Structure Characterization And Activity Of Maca Polysaccharides

Maca,as a functional food that can be used as medicine and food,has rich nutritional value.Its efficacy of anti-fatigue,improving immunity and enhancing sexual function is widely recognized and has a broad market prospect Nowadays,the research and development of polysaccharides are becoming more and more mature,and they have potential research and application value in many fields such as food,medicine and health care products.However,due to the complex extraction and purification of natural polysaccharides and the low extraction rate,most Maca polysaccharides products in the market are still dominated by crude extracts,and there is the problem of unclear medicinal substances.This study is based on the development of functional food,taking the maca polysaccharide in the raw maca root as the research object,the following four aspects are studied:（1）Optimization of Maca polysaccharides extraction rate:the method of ultrasonic-assisted hot water extraction was used to reduce the extraction temperature,and the response surface method was used to analyze the four major factors affecting the extraction rate of polysaccharides:extraction temperature,extraction time,ultrasonic power and material-to-liquid ratio.The optimization of four factors and three levels was carried out,and the best extraction conditions were obtained:extraction temperature 50℃,ultrasonic power220 W,extraction time 42 min,material-to-liquid ratio 1:32 g·m L^-1.The final maca polysaccharide extraction rate was 11.0%under optimized conditions.（2）Separation,purification and structural characterization of Maca polysaccharides:anion exchange resin DEAE-650M and dextran gel column HW-65F were used to separate the components of maca polysaccharides,and finally three components were obtained,named maca polysaccharides 1（MPS1）,maca polysaccharides 2（MPS2）,maca polysaccharides 3（MPS3）.The structures of maca polysaccharides were characterized from the aspects of monosaccharide composition,molecular weight and glycosidic bond type.（3）Antioxidant and hypolipidemic effects of Maca polysaccharides:the antioxidant activity and hypolipidemic effects of MPS were evaluated by free radical scavenging rate and cholate binding ability,respectively..MPS1 and MPS2 showed strong antioxidant activity and the scavenging rates of for DPPH free radicals were 81.8%and 63.7%,respectively.Moreover,the scavenging rates of MPS1 and MPS2 for hydroxyl free radicals were 56.8%and 76.7%,respectively.In addition,the in vitro binding rates of MPS3 to sodium taurocholate and sodium glycocholate were 49.1%and 32.3%,respectively.These studies have shown that MPS1 and MPS2 have good antioxidant activity,and MPS3 has a certain effect of lowering blood lipids.（4）Macrophage polarization and antitumor effect of Maca polysaccharides:when M0phenotype of macrophages Raw 264.7 were treated with MPS,it was found that the secretion levels of M1 markers tumor necrosis factorα（TNF-α）and NO were enhanced,and the m RNA levels of TNF-αand i NOS（inducible nitric oxide synthase）were also up-regulated,indicating that MPS can induce M1 polarization of macrophages with M0 phenotype;lactic acid,IL-4,and IL-13 were used to induce M2 polarization of macrophages with M0phenotype,and then stimulated with MPS.The results showed that the m RNA levels of Arg1and CD206（M2 markers of macrophages）were down-regulated,and the m RNA levels of TNF-αand i NOS（M1 markers of macrophages）were up-regulated,indicating that MPS can induce M1 polarization of M2 phenotype macrophages.Furthermore,the mouse melanoma cells B16F0 and B16F10 were cultured with the medium of M1 polarized macrophage,and the results showed that the inhibitory effects were obvious,and the main substance that inhibited the vitality of cancer cells was TNF-α.