Extraction And Structural Characterization Of Noni Polysaccharides

Noni is a Morinda genus plant.Its main chemical components include flavonoids,anthraquinones,and polysaccharides.Noni polysaccharide is its main active ingredient,which has a wide range of biological activities such as antitumor,antioxidant,and immune regulation.At present,Noni polysaccharides are mainly extracted by hot water and ultrasonic-assisted water extraction,and the extraction rate is only 6%～8%.Flash extraction technology relies on high-speed shear force and super-molecular diafiltration technology to maximize the retention of plant active ingredients.Therefore,this project uses orthogonal design to optimize the flash extraction of Noni polysaccharides,in order to improve the extraction rate of polysaccharides,and then isolate and purify Noni polysaccharides and characterize their structure.It is expected to provide a reference for the comprehensive development of noni polysaccharides and reduce costs for health care product manufacturers.Noni in this paper was purchased from Sanya City,Hainan Province.The flash extraction technology was used to extract Noni polysaccharides.Based on single factor experiments,the optimal extraction process conditions for Noni crude polysaccharides were obtained by orthogonal design.Sevag method was used to deproteinize and hydrogen peroxide to decolorize and remove impurities.DEAE-52 cellulose column chromatography and Sephadex G-75 column separation and purification were used to obtain Noni uniform polysaccharide.High-performance liquid chromatography,phenol-sulfuric acid method,and Coomassie brilliant blue method were used to verify the purity of five polysaccharide components and determine their molecular weights.The phenol-sulfuric acid method,the Molish reaction,the ninhydrin reaction,the biuret reaction,the I₂-KI reaction and the ferric chloride reaction were used to verify whether Noni uniform polysaccharides contained protein,nucleic acid,starch,phenols or tannins.Finally,the structure of Noni uniform polysaccharide NONI-C was characterized by ultraviolet spectrum,infrared spectrum,PMP pre-column derivatization method,Congo red experiment,particle size analysis,X-ray diffraction and scanning electron microscope.The optimal technological conditions for the extraction of Noni crude polysaccharide by flash extraction method were obtained by orthogonal design:the material-liquid ratio of 1:60,the extraction time was 50S,the extraction temperature was 70°C,and the extraction rate of Noni crude polysaccharide reached 16.08%.After cellulose and gel column chromatography,5 kinds of Noni uniform polysaccharides were finally obtained,named NONI-A1,NONI-A2,NONI-B,NONI-C and NONI-D2.According to the standard curve and retention time,the molecular weight of NONI-A1 is 36258 Da;the molecular weight of NONI-A2 is 33473 Da;the molecular weight of NONI-B is 30152 Da;the molecular weight of NONI-C is 28264 Da;the molecular weight of NONI-D2 is 24572 Da.Purity test shows that Noni uniform polysaccharide contains no protein,nucleic acid,starch,phenols or tannins.The component with the highest yield,NONI-C,was selected for in-depth research.The UV results proved that NONI-C is a carbohydrate and does not contain proteins and nucleic acids.Infrared results suggest that NONI-C is anα-pyranose.Monosaccharide composition analysis revealed that NONI-C was composed of Glc A,Gal A,Glc,Gal,Xy,and an unknown sugar.The molar ratio between monosaccharides is Gal A:Glc A:Gal:Xyl:unknown sugar:Glc=5.46:4.75:10.73:10.43:1.64:1.Scanning electron microscopy observed that NONI-C had a coral-like deposit.Congo Red experiment results showed that NONI-C had a three-stranded spiral structure.The particle size test revealed that the average particle size of NONI-C was172.8 nm.In this study,five types of noni polysaccharides were extracted,separated and purified from Noni for the first time,and the physical and chemical analysis methods were used to characterize the structure of the component with the highest yield,NONI-C.The preliminary structure of Noni polysaccharide NONI-C was revealed,which provided a theoretical basis for the structure-activity relationship research of Noni polysaccharide and provided data support for the comprehensive development of Noni polysaccharide.