| Dietary polyphenols have excellent bioactivities such as anti-inflammatory,antioxidant,and intestinal regulation,and have a wide range of applications in health food and biomedical fields.However,its poor water solubility and stability,susceptibility to oxidative degradation,low oral bioavailability and many other factors limit its application in practical production.Therefore,it is important to improve the stability and bioactivity of dietary polyphenols by constructing green and safe foodbased oral delivery systems.Mesona chinensis Benth is an economically important plant resource,which is commonly used to make "black gel".Mesona chinensis polysaccharide(MCP)is an acidic heteropolysaccharide extracted from Mesona chinensis Benth,which is the main active ingredient.Studies have shown that MCP has good gel properties and biological activities.In this work,a novel oral intestinal delivery system was developed and designed for loading dietary polyphenols based on MCP and zein.The formation mechanism,stability,functional properties,and bioactivities of the system were investigated.It also investigated the nutritional intervention mechanism of the targeted delivery system for dietary polyphenols in ulcerative colitis(UC)from the perspectives of molecular biology,intestinal flora,and metabolomics.The main findings are as follows:(1)Construction of MCP-zein nano-delivery system and its characterization.Mesona chinensis polysaccharide(MCP)was extracted and characterization.Results showed that MCP is an acidic polysaccharide with a molecular weight of 183 k Da.The monosaccharides were composed of galacturonic acid,rhamnose,arabinose,galactose,glucose and glucuronic acid.Based on the 1D/2D NMR results,the main chain structure was presumed to have the presence of α-1,4-Galp A repeat linkage units and branched residues of α-L-Rhap.By antisolvent precipitation method,MCP can form nanoparticles(Z-MNPs)with shell-and-core structure with zein(zein)without the need of cross-linking agent and heat treatment.The formation of nanoparticles was related to the MCP concentration,p H,and preparation process.The optimum conditions were 0.05% MCP with 2% zein at p H 7.The nanoparticles were prepared with good homogeneity and an average particle size of <250 nm.Interaction studies revealed that electrostatic interaction forces,hydrophobic interaction forces,and disulfide bonding were the main driving forces in the formation of Z-MNPs.In addition,the Z-MNPs have good room temperature storage stability and redispersion properties,which are favorable for subsequent applications.(2)Z-MNPs efficiently load dietary polyphenols to improve their in vitro stability and cellular uptake.To evaluate the performance of Z-MNPs for encapsulating dietary polyphenols,curcumin(Cur)was chosen as the research model,and Results showed that the encapsulation rate was > 90%.FTIR,XRD,fluorescence spectroscopy and molecular docking results indicated that the embedding process of curcumin by Z-MNPs involved hydrogen bonding,hydrophobic interactions and van der Waals’ forces.Z-MNPs effectively enhance the thermal stability,UV stability,chemical stability in physiological environment,and bioaccessibility of curcumin.In addition,curcumin-loaded NPs(ZMC NPs)exhibited p H-responsive controlled release behavior in the gastrointestinal environment,with less release in the acidic environment of the stomach and more release in the more neutral intestinal environment.Cytotoxicity assays showed that Z-MNPs had good cytocompatibility and no significant cytotoxicity.Cellular uptake experiments showed that Z-MNPs could promote the uptake of the encapsulated substances by Caco-2,and the cellular uptake efficiency decreased with the increase of MCP concentration and showed some timedependent characteristics.(3)Construction of dietary polyphenol-loaded colon-targeted delivery system by combined water evaporation cross-linking method.To further increase the stability of nanoparticles in the gastrointestinal tract,colon-targeted nanoparticles(AW-ZmNPs)were prepared by combining the antisolvent precipitation method and water evaporation cross-linking method.Compared to Z-MNPs,AW-ZmNPs exhibited smaller particle size(<176 nm)and more surface charge(-34 m V).Results of SDS gel electrophoresis,protein digestibility,and circular dichroism showed that AW-ZmNPs exhibited better gastrointestinal stability than Z-MNPs.In addition,AW-ZmNPs showed higher encapsulation efficiency for dietary polyphenols(curcumin and resveratrol),and the encapsulation mechanism was closely related to the structure of both.In vitro simulated gastrointestinal release experiments showed that AW-ZmNPs had a better slow-release ability and could reduce the release of dietary polyphenols in the stomach and small intestine regions.In vivo distribution experiments in mice of AW-ZmNPs showed that AW-ZmNPs could promote the accumulation of encapsulated substances in the colon,increase the retention time of the colon,and promote the uptake of colon macrophages,which had a better colon-targeting property.In vivo safety experiments in mice showed that AW-ZmNPs had good in vivo biosafety,and there was no significant difference between AW-ZmNPs and healthy mice in terms of blood counts,organ indices,liver indexes and tissue structure after continuous oral administration.(4)Dietary polyphenol-loaded AW-ZmNPs effectively alleviate colitis.DSSinduced ulcerative colitis(UC)mouse model was constructed to evaluate the alleviating effects of dietary polyphenol-loaded AW-ZmNPs on UC symptoms.Results showed that oral administration of curcumin(Cur-aw NPs)-loaded and resveratrol(Resaw NPs)-loaded AW-ZmNPs could effectively alleviate the symptoms of weight loss,diarrhea,blood in stool,and shortening of colon in UC mice,reduce the damage of colon tissues,and promote the recovery of colon structure and function.Compared with free dietary polyphenols,Cur-aw NPs have more significant effects in inhibiting intestinal inflammation,and can reduce the expression of inflammatory factors in the intestine by inhibiting the expression of TLR4 and the phosphorylation of key proteins in the MAPK pathway.Cur-aw NPs also increase the expression of tight junction proteins in colonic tissues,reduce the levels of ET and LBP in serum,and improve intestinal barrier function.And Res-aw NPs could regulate the balance of intestinal immune cells and increase the expression of anti-inflammatory factors and intestinal barrier-associated factors(e.g.,IL-2,TGF-β,and IL-22).Res-aw NPs could regulate the ratio of CD3+,CD4+,and CD8+ T splenic lymphocytes,effectively regulating the immune balance in UC mice.In addition,Res-aw NPs exhibited significantly better in vivo antioxidant activity,effectively reducing the level of oxidative stress,decreasing the MDA content,and increasing the activities of antioxidant enzymes.(5)Construction of dietary polyphenol co-delivery system and its nutritional intervention on UC.AW-ZmNPs were used for the co-embedding treatment of curcumin and resveratrol,and results showed that AW-ZmNPs had a very good coembedding effect,and the embedding rate was greater than 88%.Dietary polyphenol co-delivery systems(CR-NPs)exhibited similar slow-release behaviors in a simulated gastrointestinal environment in vitro.However,the two differed in the amount of release at different stages,which might be caused by the differences in the interactions with the nanoparticles due to the different structures of the two.Subsequently,the effect of the co-delivery system on DSS-induced ulcerative colitis(UC)was assessed,and Results of animal experiments showed that CR-NPs could effectively alleviate the adverse symptoms of DSS,such as weight loss,increase in DAI index,and disruption of intestinal structure and function.The co-delivery system demonstrated good in vivo anti-inflammatory effect and antioxidant activity,which could intervene in the development of UC by improving the intestinal barrier function and regulating the immune balance of the body.The co-delivery system helps to reduce the intake of single substances and increase nutritional diversity,thus providing good nutritional intervention.(6)The nutritional intervention mechanism of dietary polyphenol delivery system in UC mice was investigated by gut flora and metabolomics.AW-ZmNPs can effectively target dietary polyphenols to colon tissues and increase their interactions with intestinal flora.16 S r RNA sequencing results showed that dietary polyphenol-loaded AW-ZmNPs had a positive regulatory effect on the composition and ecological structure of gut microorganisms in mice with ulcerative colitis(UC).ecological structure of ulcerative colitis mice,which could improve the species diversity and abundance of the intestinal flora of UC mice,maintain the structure of the intestinal flora of mice,and reduce the intestinal flora imbalance caused by DSS.In addition,all dietary polyphenol-loaded AW-ZmNPs significantly increased the production of short-chain fatty acids and improved intestinal health after intervention.The mechanism of improvement of ulcerative colitis by oral colon-targeted delivery system of dietary polyphenol-loaded AW-ZmNPs was further investigated by metabolomics.The metabolomics results of both serum and faecal samples showed that more than a dozen differential metabolites were identified between the control and model groups,and between the dietary polyphenol delivery and model groups.A number of metabolites,including tryptophan,linoleic acid and arachidonic acid,were disrupted in the model group,whereas the dietary polyphenol-targeted delivery system was effective in regulating metabolite levels in UC mice.Metabolic pathway analysis showed that the targeted delivery of dietary polyphenols mainly affected primary bile acid biosynthesis,linoleic acid metabolism,riboflavin metabolism,tryptophan metabolism,and arachidonic acid metabolism.Correlation analyses showed significant correlations between riboflavin,tryptophan,arachidonic acid and linoleic acid and inflammatory factors,which can be used as potential biomarkers. |
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