Structural Characterization And Biological Activity Of Polysaccharides From Corn Silk

Corn silk(Zea mays L.),which belongs to Gramineae,is the female stigma of dried maize and is mainly distributed in Asia.Corn silk is an important and traditional Chinese herbal medicine.At present,the research on the active ingredients of corn silk is mainly focused on the flavonoids of corn silk.The research on polysaccharides of corn silk is still in the primary stage,such as the extraction method,purification and isolation methods,and primary structure identification of corn silk polysaccharides.In this paper,corn silk polysaccharides were extracted,isolated and purified from corn silk collected in suburban Jilin City,and homogeneous components of corn silk polysaccharides were obtained.And the structure and biological activity of Polysaccharides from corn silk were also studied.The main conclusions are as follows:1.Crude polysaccharide of Corn silk was extracted by hot water reflux method.Then cotton-like DEAE cellulose was used to purify crude polysaccharides from corn silk,and impurities such as protein and pigment were removed.After the preliminary separation of DEAE-52 anion exchange resin chromatography column,D-CSP-1,D-CSP-2,D-CSP-3,D-CSP-4 and D-CSP-5 were obtained from corn silk polysaccharides.After five components were collected,concentrated,dialysated and freeze-dried,they were further purified by Sephadex G-150 chromatography column,and CSP-1,CSP-2,CSP-3,CSP-4 and CSP-3 were obtained.2.The structure of polysaccharides from corn silk was identified.In ultraviolet analysis,CSP-1,CSP-4 and CSP-5 had absorption at 280 nm and 260 nm in UV analysis,indicating that the CSP-4 and CSP-5 contained protein and nucleic acid,and the CSP-1,CSP-2 and CSP-3 were absence of protein and nucleic acid.Infrared results showed that the infrared spectra of CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 all had characteristic absorption peaks of O-H,-CH3 or-CH2,C-O,which were the characteristic structures of polysaccharides,and the CSPs were polypyran.The molecular weights of CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 were 5.86 ? 105 Da,1.58 ? 106 Da,8.13 ? 105 Da,1.04 ? 106 Da and 8.62 ? 105 Da,respectively.The monosaccharide composition of CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 were very similar,but their molar ratios were different.It also showed that the main components of corn silk polysaccharide were mannose,glucose and galactose.Secondly,there is a certain amount of rhamnose,arabinose,glucuronic acid and xylose,and finally contains a small amount of ribose and fucose.The skeletons of five CSPs were mainly composed of 1?4,1?6,1?3,6 and ?1.The types of glycoside bond links were similar,but the proportions wre different.1H-NMR and 13C-NMR spectra showed that CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 had a large number of ?-glycoside bonds and a small amount of ?-glycoside bonds.There were no triple helix conformation in CSP-1,but triple helix conformation exists in CSP-2,CSP-3,CSP-4 and CSP-5 in solution.3.In vitro DPPH and ABTS free radical scavenging activity of CSPs were determined.The IC50 of scavenging capacity of VC,CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 on DPPH free radicals were 0.06 ± 0.0014 mg/m L,1.30 ± 0.0039 mg/m L,0.46 ± 0.0067 mg/m L,2.71 ± 0.0070 mg/m L,0.67 ± 0.0057 mg/m L,0.99 ± 0.0077 mg/m L respectively.The IC50 of ABTS free radical scavenging capacity were 0.02 ± 0.0033 mg/m L,0.23 ± 0.0071 mg/m L,0.15 ± 0.0057 mg/m L,0.63 ± 0.0074 mg/m L,0.56 ± 0.0052 mg/m L and 0.45 ± 0.0075 mg/m L,respectively.The results showed that the five components of Corn Silk Polysaccharide had certain antioxidant activity,but the antioxidant ability was different in different antioxidant systems.Considering the results of the two systems,the antioxidant activity of CSP-2 was the strongest,possibly related to the arabinose with high galactose content in CSP-2.The effects of five polysaccharides from corn silk on the proliferation,phagocytosis and NO secretion of RAW264.7 cell line were studied.The results showed that CSP-1,CSP-2 and CSP-3 had strong immunoregulatory activity,while CSP-4 and CSP-5 had very low immunoregulatory activity.The inhibitory effects of five CSPs on lung cancer cell A549 were explored.The results showed that CSP-2 and CSP-5 had significant inhibitory effects on lung cancer cell A549.In summary,Corn Silk Polysaccharide had antioxidant,immunoregulatory and antitumor activities.The results showed that the purified components CSP-1,CSP-2,CSP-3,CSP-4 and CSP-5 of corn silk polysaccharide could be used as a new type of human edible nutrient,which laid a scientific foundation for the development and utilization of agricultural waste corn silk.