Fabrication Of Curcumin-loaded Gastrointestinal Controlled Release Carrier And Its Bioaccessibility

Curcumin(Cur)is a relatively safe polyphenolic compound with physiological functions such as anti-inflammatory,antioxidant and hypolipidemic functions,in addition,it can also be used as an effective drug for the treatment of inflammatory bowel diseases(IBDs),but due to its high hydrophobic properties,chemical instability and extremely fast metabolism,it cannot maintain enough content after entering the blood circulation system and gastrointestinal tract to exert its beneficial biological activities,resulting in extremely low bioaccessibility,which greatly limits its application in the food and pharmaceutical industry.Therefore,it is urgent to build a delivery system that can achieve high curcumin loading,gastrointestinal controlled release and high bioaccessibility.In recent years,oleogels have attracted much attention because of their self-assembled gel network structure synergistic surfactants with solubilization and slow release of active ingredients,but their gastrointestinal protection effect on curcumin was poor,while p H-responsive polymers had good gastrointestinal controlled release properties.Therefore,this paper combined these two systems through the seamless dripping pill embedding technology to prepare an emerging carrier that can achieve high bioavailability of curcumin.Enteric oleogels loaded with curcumin were prepared using candelilla wax(CLW)as gelling agent and sunflower lecithin(SFL)as surfactant,and then seamless drop embedding technology and p H-responsive polymer composed of carrageenan(IC)and gellan gum(GG)were used to construct curcumin-loaded controlled-release carriers,in order to achieve gastrointestinal controllable release,high bioaccessibility transformation and improvement of intestinal flora diversity with high content of curcumin,thereby enriching the types of curcumin delivery systems.To provide a theoretical basis for the application of curcumin in the food and drug industry,the main research results were as follows:Firstly,whether curcumin decrystallization could be achieved by high-temperature treatment,and the effects of different sunflower lecithin contents(0,1,3,5,10%)on the gel structure of candelilla wax-based oleogels(0%SFL,1%SFL,3%SFL,5%SFL,10%SFL)were explored.After high temperature treatment of curcumin,its crystal structure disappeared,in a completely dissolved state,the content could reach 2.7%,and the addition of different sunflower lecithin content would not change the crystal structure of the oleogels(β′ type),but with the increase of sunflower lecithin content,the gel network structure of the oleogels gradually became loose,and the thermal stability,gel strength and hardness of the oleogels gradually decreased.In addition,the addition of different levels of sunflower lecithin did not change the peak position of the oleogel.The above results showed that decrystallized curcumin oleogels with controllable gel network structure,thermal stability,rheology and texture properties could be obtained by high-temperature heating and adjusting the addition amount of sunflower lecithin.Furthermore,the effects of different sunflower lecithin contents on the environmental stability(ultraviolet light,storage,in vitro release)and gastrointestinal digestion stability of decrystallized curcumin loaded in the oleogels were explored to construct an enteric oleogel.The transparency of the oil-gelled curcumin sample decreased significantly,which could realize the slow release of curcumin and the improvement of environmental stability.Decrystallization of curcumin could significantly improve its bioaccessibility.With the increase of sunflower lecithin addition,the degree of lipolysis of curcumin oleogel samples increased,and the UV stability,storage stability,in vitro release and bioaccessibility of the loaded curcumin also gradually increased,but the retention rate gradually increased.When the amount of sunflower lecithin was increased to 10%,the curcumin oleogel sample lost its gel structure in the simulated intestinal digestive juice,and an enteric oleogel was successfully constructed,and the bioaccessibility of curcumin loaded on it reached the highest.Finally,with enteric oleogel(10% SFL)as the core material,p H-responsive polymers composed of different ratios of carrageenan and gellan gum(1:0,4:1,2:1,1:1,1:2,1:4)were used as the wall material,and the two were combined by seamless drop embedding technology to prepare curcumin-loaded gastrointestinal controlled-release carrier(GG＿ICB).Through the investigation of viscosity,temperature frequency scanning and texture characteristics,the optimal ratio of carrageenan and gellan gum as wall materials was screened out as 1:2.The speed of gel formation at low temperature in this ratio,the gel strength and mechanical strength were moderate,and the GG＿ICB heat resistance obtained by this ratio was excellent.The swelling rate of GG＿ICB rose in simulated saliva fluid(SSF)and simulated intestinal fluid(SIF)without complete swelling,in simulated gastric juice(SGF),the degree of swelling decreased,and when simulating colonic fluid(SCF),due to the action of characteristic enzymes,the swelling degree reached 100%,and the GG＿ICB shell disappeared.Compared with 10% SFL,compared with 10% SFL,the GG＿ICB curcumin content released into the digestive juice was less than 1% after the end of the simulated small intestine,and the retention rate was significantly improved,while the content of curcumin measured in the digestive juice increased significantly after 4 h of simulated colonic digestion,and the above results indicated that GG＿ICB had gastrointestinal response properties,which could greatly improve the gastrointestinal stability of curcumin,and realize the colonic delivery and release of high-content curcumin.In vitro fermentation studies have shown that pure curcumin powder(Curp)and GG＿ICB-encapsulated curcumin could significantly increase the diversity of human intestinal flora,but GG＿ICB could significantly reduce the relative abundance of Proterobacteria.In addition,GG＿ICB could promote the proliferation of beneficial bacteria such as Bifidobacteria,Faecalibaterium and Blautia that could improve intestinal barrier,change intestinal carbohydrate metabolism and IBDs due to its shell containning dietary fiber,which is expected to be a good carrier for regulating the balance of intestinal flora,treating colon inflammation and reducing obesity.