Identification Of Structure Of Polysaccharides From Fructus Mori,and The Effect Of Iron Modification On Structure And Activity Of Polysaccharide

Fructus Mori is a kind of"medicinal and food homologous"fruit with high economic and nutritional value.The Fructus Mori fruits have various active substances,including flavonoids,polyphenols,resveratrol,polysaccharides and Vitamin,and have good anti-inflammatory,anti-tumor,anti-oxidation,hypoglycemic and hypolipidemic activities.However,the fine structure analysis,the effects of extraction and modification,and structure-activity relationship of the polysaccharides from Fructus Mori fruits are still unclear.Therefore,in the present study,the effect of extraction temperature on the physiological activity and structure of polysaccharides from Fructus Mori fruits?designated as MFP?were investigated.Furthermore,the fine structure of MFP was identified by chemical and instrumental analysis.Finally,the effects of Fe???modification on the structure and activity of MFP were studied by preparing two different complexes of MFP and Fe???.This study aimed to provide theoretical basis for the development and application of MFP as following:?1?The polysaccharide?MFP?was extracted at 30? and 90?,and the MFPs-30-60,MFPs-30-80,MFPs-90-40,MFPs-90-60 and MFPs-90-80 were obtained by fractionation and alcohol precipitation with 40%,60%and 80%ethanol.Ion chromatography?IC?analysis showed that all the polysaccharide fractions contained the same monosaccharides with different molar ratios.High performance liquid chromatography?HPLC?analysis indicated that the molecular weight distribution of all the polysaccharide fractions were different that high temperature caused polysaccharide degradation.Infrared spectrum?FTIR?analysis and atomic force microscope?AFM?showed that all the polysaccharide fractions had similar functional groups but with different particle size and initial structure.In vitro activity experiments indicated that the five polysaccharide fractions had different antioxidant,hypoglycemic,and hypolipidemic activities.MFPs-30-80 with low molecular weight showed the strongest antioxidant activity.MFPs-30-80 and MFPs-90-40 with higher glucose and uronic acid contents showed strong inhibitory effect on?-amylase and?-glucosidase.In addition,MFPs-90-40,MFPs-90-60 and MFPs-30-60 displayed strong bile acid-binding ability,which may be due to the high uronic acid content and molecular weight.?2?The MFPs-90-40 was fractionated by DEAE-52 cellulose column and 27%ethanol alcohol precipitation to obtain MFP1P with molecular weight of 56.78 k Da and carbohydrate content of 93.32±0.54%.MFP1P was composed of glucose,galactose,galacturonic acid and mannose with molar ration of 66.62%,13.94%,18.24%and1.20%,respectively.Methylation and nuclear magnetic resonance?NMR?analyses indicated that MFP1P consisted of?3)-?-D-Gal-(1?,?-D-Man-?1?and?6?-?-D-Glc-(1?.Dynamic light scattering?DLS?,size exclusion chromatography coupled with multiple detectors?SEC-MALLS?,AFM,transmission electron microscopy?TEM?and scanning electron microscopy?SEM?showed that MFP1P exhibited a uniform spherical chain structure.In vitro antioxidant experiments showed that it had good antioxidant activity.?3?The MFPs-90-40 was separated and purified by DEAE-52 cellulose column to obtain MFP1,MFP2 and MFP3,and MFP1 was the main component.The monosaccharide composition in MFP1,MFP2 and MFP3 was same but with different ratio.MFP1 and MFP2 have two molecular weight distribution peaks,while MFP3 has a uniform molecular weight distribution.In addition,MFP1,MFP2 and MFP3 were used to prepare MFP1-Fe,MFP2-Fe and MFP3-Fe three kinds of polysaccharide iron???complexes.The chelate mechanism of iron???and polysaccharide was proposed that iron???as a core is enwrapped by the polysaccharide as a ligand by hydroxyl and carboxyl groups,which induced a morphology change from flat sheets to rods and increased the size.Furthermore,MFP showed strong antioxidant activity eliminating hydroxyl radicals and inhibitting MDA production in healthy mouse liver homogenate.Also,the MFP-Fe???chelates exhibited stronger superoxide radical scavenging ability than MFP.?4?The mulberry fruit polysaccharide iron nanoparticles corresponding to MFP1,MFP2 and MFP3 were prepared by a positive co-precipitation method,namely Fe₃O₄@MFP1NP,Fe₃O₄@MFP2NPs and Fe₃O₄@MFP3NPs.The Fe₃O₄@MFPNPs showed characteristic absorption peak of Fe-O bonds in the FTIR,and they showed higher?-helix,anti-parallel and?-sheet content but lower parallel,random curl content in the circular dichroism spectrum?CD?.Microscopic morphology showed the spherical Fe₃O₄@MFPNPs with particlen size distribution in the ranges of 3-10 nm and 68-164nm,which were smaller than the MFP?20-25 nm and 125-200 nm?,and the MFP-Fe???complex?190-220 nm and 450-615 nm?.At the same time,the antioxidant activity and absorption of polysaccharides after spheroidization were significantly improved.The half inhibitory concentrations(IC₅₀)of hydroxyl radicals of Fe₃O₄@MFP1NP,Fe₃O₄@MFP2NPs and Fe₃O₄@MFP3NPs were 0.11±0.002,0.12±0.008 and 0.17±0.01mg/m L,which were lower than that of MFP1,MFP2,MFP3 and Fe₃O₄?0.14±0.02,0.20±0.02,0.33±0.005 and 5.89±0.11 mg/m L?.The IC₅₀ values of superoxide radicals were 0.38±0.01,0.55±0.01 and 0.39±0.02 mg/m L,respectively,which were also lower than MFP1,MFP2,MFP3 and Fe₃O₄?2.14±0.17,6.64±0.11,6.24±0.41 and261.08±0.99 mg/m L?.And the ability of Fe₃O₄@MFPNPs to inhibit MDA production in mouse liver tissue was still the strongest.Furthermore,the intestinal absorption analyses showed the cumulative absorption amount of Fe₃O₄@MFPNPs were increased from 1505.26±11.78,1446±10.63 and 1634.53±12.21?g of the original polysaccharide to 1762.63±9.13,1718.44±9.15 and 1882.28±8.76?g,respectively.