Study On The Corelation Between Molecular Modification And Property Of Konjac Glucomannan

Konjac glucomannan(KGM)is a water-soluble non-ionic polysaccharide produced from the tubers of Amorphophallus konjac C.Koch.,which has especial biological functions,such as help lose weight,excretion,reduce serum lipid and blood glucose,and etc.Thus,it can prevent obesity,intestinal cancer,cardiovascular diseases,diabetes and so on.It has been widely used in food and medical fields.Molecular modification can effectively improve the biological function of polysacharride.Molecular modification of polysaccharide is to obtain more derivatives of all kinds of structure types through modifying compound's structure by chemical,physical,and biological methods.It influence biological activities of polysaccharides through affecting their spatial structure,molecular mass,and the kinds,quantities and positions of substitution groups in polysaccharide.There were many reports about molecular modification of KGM,for example esterification,graft copolymerization,deacetylation,etherification,crosslink,etc.However,the effect of konjac glucomannan on calcium oxalate crystal morphology,the relationship between structure and properties of sulfated and aminated KGM has not been reported.In this work,we study influence of KGM on crystallization morphology and structure of calcium oxalate,the structure of sulfated KGM,hydrogen bond sites of sulfated KGM(SKGM)in solution,the interactions between SKGM and target effect on coronary heart disease,the structure and conformation stability of aminated KGM.hydrogen bonding network structures of amino-konjac glucomannan-zinc chelate,etc.by modern analysis methods combining with molecular simulation and molecular docking technology.(1)Influence of Konjac Glucomannan on Crystallization Morphology and Structure of Calcium OxalateInfluence of different KGM additions on crystallization morphology and structure of calcium oxalate has been investigated by infrared spectroscopy,scanning electron microscope,x-ray diffraction and so on.The results showed KGM can complex with Ca2+ ions in solution.Low concentration KGM prevent calcium oxalate crystals from aggregating,increase the concentration of ions in solution,thus reduce the number of the crystals,inhibit their growth,and the shape of crystals are more round.While high concentration KGM promote the growth of the crystals and the shape are sheet or irregular.Only calcium oxalate monohydrate was observed whether in the absence or presence of KGM in a certain system.(2)Sulfation Modification of Konjac Glucomannan and its Structural ElucidationTwo derived sulfated polysaccharide of Konjac glucomannan(KGM)with degree of substitution(DS)of 0.38 and 0.59,named KGMS1 and KGMS2,were obtained using a sulfuric acid/n-butanol method at 0? and 10? respectively.The content of SO42-in polysaccharide sulfate was determined by barium sulfate turbidimetry,then the structure of polysaccharide sulfate was elucidated by UV,IR,CD,SEM and TGA.The results show sulfated compounds formed.The content of SO42-is 6.037%and 8.525%respectively.The characteristic bands of sulfate ester bond of KGMS1 and KGMS2 are at a wavelength of 1248 cm-1,809cm-1 and 1252cm-1,810cm-1 respectively.Comparing with original KGM,the negative CD spectrum below 201 nm is larger for sulfated KGM,which is attributable to sulfate group.Its microstructure become more compact.The thermal stability of KGM sulfate is lower than that of KGM,and the decomposition temperature of KGM and SKGM2 is 260?and 200?,respectively.(3)Molecular Docking of Sulfated Konjac Glucomannan and Target of Coronary Heart DiseaseEnergy and the site of hydrogen bonds of the fraction of konjac glucomannan(KGM)and sulfated konjac Glucomannan(SKGM)are predicted in the approach of molecular simulation.And the interactions of KGM and SKGM with target effect on coronary heart disease,namely peroxisome proliferator activated receptor y(PPAR-y),are investigated.The results showed that the total energy of SKGM in the solution are lower than KGM.It means sulfation can improve the solubility of KGM.The keylinking points of hydrogen bonding network of the fraction of KGM are at the 0 of glycosidic bond,01 and 06 of mannose(3).The key linking points of hydrogen bonding network of the fraction of SKGM are at the 0 of 2-OH of glucose(2),O1 and 06 of mannose(3).The docking results suggest that SKGM can interact with the target better than KGM.SKGM binds to the active site under the help of hydrogen bonds and hydrophobic interaction.(4)Studies on Molecular Chain Conformation Stability of Aminated Konjac GlucomannanKonjac glucomannan(KGM)was aminated through the reaction of 2-chloroethyl-amine(CEA)with KGM.The modification was carried out under different conditions(concentration of CEA based on the gram of KGM,concentration of NaOH,reaction time and temperature).Aminated KGM(AKGM)was characterized by IR.And molecular simulation technology was adopted to analyze its conformation stability.The results indicated that the extent of amination increases significantly by increasing CEA concentration from 5%to 25%.The optimum concentration of NaOH,reaction time and temperature are 10%NaOH,70?,45min,respectively.IR shows KGM are successfully aminated.The conformation of AKGM is a ruleless clew-like size.(5)Studies on Hydrogen Bonding Network Structures of amino-konjac glucomannan-zinc ChelateAmino-Konjacglucomannan(NH2-KGM)was prepared through the reaction of ammonium hydroxide with KGM by ultrasonic.The influence of amount of ammonium hydroxide,concentration of KGM and ultrasonic time on the extent of amination were studied.Then,NH2-KGM and zinc sulfate were used as materials for the preparation of NH2-KGM-Zn complex.The results indicated that the extent of amination increased with the increasing of ammonium hydroxide.The optimum concentration of KGM and ultrasonic time are 0.3%and 75min,respectively.IR showed KGM is successfully aminated and NH2-KGM form stable complex with zinc(?).The hydrogen bonding network structures of NH2-KGM-Zn are more stable and the key linking points of hydrogen bonding network are at the OH(6)and O(3)positions of mannose and OH(2)of glucose and O(3)of mannose on KGM ring.It is more favorable for NH2-KGM-Zn to form intermolecular hydrogen bonds between KGM.