The Composition And Structure Of Noni Fruit Polysaccharide And Its Therapeutic Effect In IBD Mice

Noni(Morinda Citrifolia L.)is a perennial tree or shrub belonging to the Rubiaceae family;it is cultivated in the tropics and subtropics,including Polynesia,India,Cambodia,South America,and Hainan Province of China.Noni fruit has been proven to have the function of anti-inflammation,reducing fat and body weight,improving diabetes,and so on.Polysaccharide is the main biologically active ingredient of Noni fruit.In this study,the polysaccharide extracted from Noni fruit was fractionated and purified.Further,the structure of Noni fruit polysaccharide(NFP)was characterized.Finally,the anti-inflammatory activity of the NFP was discussed.The main results and conclusions of the study are summarized as follows:1)The influence factors of extraction time,extraction temperature and liquid-to-material ratio on NFP were investigated by orthogonal optimization.The results showed that the most important factor affecting the yield was the liquid-to-material ratio,followed by the extraction time,and the extraction temperature was less.The optimal parameters for this method were extraction time of 55 min,extraction temperature of 95 ?,liquid to material ratio of 20 mL/g.Under this condition,the extraction rate of the polysaccharides could exceed 4%.2)The molecular weight of the NFP fractionation purification system was determined to be 456 kDa by Gel Permeation Chromatography(GPC).The chemical structure of NFP was characterized using ion chromatography.The result of ion chromatography analysis showed that NFP mainly consisted of five monosaccharides,including galacturonic acid,galactose,glucose,rhamnose and arabinose,whose relative content of monosaccharide were 58.44%,4.44%,21.13%,4.84%,2.16%,respectively.The results of methylation analysis and Nuclear Magnetic Resonance(NMR)analysis indicated that NFP,belonging to pectin polysaccharide,composed of Homogalacturonan(HG)domain and Rhamnogalacturonan ?(RG-I)domain and a small amount of starchy material.The HG domain is a linear polysaccharide chain polymerized by ?-1,4-GalAp,and may be substituted by acetyl group at O-2 or O-3 position.The main chain of RG-I domain consisted of [?2)-?-L-Rhaf-(1?4)-?-D-GalAp-(1?]n repeating disaccharide unit,and C4 position may bind Arabinogalactan(AG)and arabinan.3)The anti-inflammatory effect of NFP was studied via Dextran Sodium Sulfate(DSS)-induced Inflammatory Bowel Disease(IBD)mice model.The results showed that the body weight of mice induced by DSS continued to decrease,while the scores of DAI were increased compared with normal mice,whereas the administration of NFP could alleviate this symptom.Further,comparison of the colon length of mice revealed that NFP could inhibit the shortening of colon length in IBD mice.As shown by the Hematoxilin Eosin(HE)staining results of the colon sections,IBD mice have many erosions on their epithelial surface due to severe colitis.By contrast,there are only mild inflammation in NFP-administrated mice,indicating that the administration of NFP reduced the inflammatory infiltration and crypt damage caused by DSS.The results of Immunofluorescence(IF)and Alcian Blue and Periodic Acid Schiff(AB-PAS)staining showed that the administration of NFP not only promoted the secretion of mucus by mice goblet cells,but also promoted the secretion of tight junction proteins Zonula Occludens(ZO-1)and Occludin to further protect the intestinal permeability,thereby protecting the intestinal mucosa.In summary,this study fully elucidated the structural characteristics of NFP and confirmed its effectiveness in treatment of IBD mice by repairing intestinal mucosal barrier,which will lay the foundation for the development and utilization of Noni fruit.