Extraction,Purification,Structural Characterization And In Vitro Profitability Of Polysaccharides From Polygonatum Cyrtonema Hua

Polygonatum cyrtonema Hua(PCH)is one of the basal plants in the herb genus Polygonatum,as well as a rich herbal resource for medicinal and food use in China,with high nutritional and economic valuations.Modern pharmacological researches have revealed that PCH not only exhibits the efficacy of lowering blood sugar and blood lipid,anti-cancer,anti-inflammatory and anti-bacterial,but also plays a critical role in anti-fatigue,immunomodulation,anti-aging and other pharmacological effects.Polysaccharides consist of a class of natural macromolecular carbohydrates with complex and diverse structures,which are also the main active ingredients in PCH.At present,the research on PCP mainly focused on the optimization of extraction process,characterization of structural properties and investigation of biological activity,but there were fewer studies on the structure identification of pure fraction of PCP.In addition,most studies on the bioactivity of PCP have been concerned with immunomodulatory,antioxidant,and antitumor effects,but there was a lack of exploration on their intestinal health effects.In this paper,the PCP was extracted by water extraction and alcoholic precipitation method,systematically discussed in terms of its isolation and purification,structural properties,antioxidant and probiotic properties in vitro.It was aimed to provide more information for the investigation of the structural properties of PCP,and also to lay the theoretical foundation for the exploitation of the resources of PCH.The main research contents are as follows:(1)The quality evaluation of PCH resources.The polysaccharides were prepared from five different sources of PCH by aqueous extraction and alcoholic precipitation,and their structural properties and antioxidant activities were initially investigated.It was found that the polysaccharide contents of the five kinds of PCH ranged from 7.63% to 16.78% in mass fraction,with significant differences among them(p<0.05),and the highest polysaccharide content(16.78%)was recorded in PCH from Tonggu,Jiangxi.All five kinds of PCP were heteropolysaccharides,the monosaccharide composition was dominated by fructose,and all of them possessed typical sugar absorption peaks.In addition,they showed a certain antioxidant capacity in the concentration range of 2～10 mg/m L,and presented dose dependence,with the best antioxidant activity of PCP from Tonggu,Jiangxi.(2)The isolation and purification of PCP from Tonggu.Three polysaccharide fractions(PCP-50%,PCP-70% and PCP-80%)were isolated and purified from PCP of Tonggu by graded alcoholic precipitation method,and their basic physicochemical properties were analyzed.The results suggested that the PCP-80% fraction produced the highest yield(10.33±0.11%),with a total sugar content of(88.96±0.60%)and less glyoxalate and protein content.The molecular weight results indicated that PCP-50% and PCP-70% were heteropolysaccharides,while the PCP-80% fraction was a homogeneous pure polysaccharide with a relative molecular mass of 4.1 k Da.Additionally,PCP-80% presented a high relative crystallinity and good thermal stability.(3)The structural characteristics analysis of PCP-80% fraction.The structure of PCP-80%,a homogeneous fraction of PCP was elucidated by ion chromatography,FT-IR,methylation treatment and NMR instrumentation and methods.It turned out that PCP-80% exhibited the characteristic functional groups of polysaccharide compounds and contained both pyranose and furanose.The microscopic morphology was smooth and irregular porous lamellar structure.The monosaccharide composition results revealed that PCP-80% consists of fructose and glucose in a ratio of 15:1.The sugar chain of PCP-80% mainly consisted of T-Glcp-(1→,→6)-Fruf-(2→,→4)-Glcp-(1→,→2)-Fruf-(1→ and →1,6)-Fruf-2 structural fragments,of which → 6)-Fruf-(2 → was the high content at 31.35%.The results of NMR further confirmed that PCP-80% was probably composed of →6)-Fruf-(2→ as the main chain.(4)Evaluation of PCP-80% fraction for its antioxidation and in vitro probiotic properties.The antioxidant activity of PCP-80% was analyzed.While,the effect of PCP-80% on the yield of SCFAs and the community structure of intestinal microorganisms was investigated based on an in vitro simulated colonic fermentation model.PCP-80% was discovered to display some scavenging ability for DPPH radicals,hydroxyl radicals and ABTS radicals,with the strongest scavenging effect on ABTS radicals.In addition,PCP-80% was able to significantly affect the p H value and effectively promote the production of SCFAs such as acetic acid,propionic acid and n-butyric acid compared to the blank group.Besides,PCP-80% could be used as a carbon source to increase the relative abundance of beneficial genera such as Megamonas,Bifidobacterium and Phascolarctobacterium in the intestinal microorganisms,thus producing probiotic activity.