| Fatty acid starch ester is a new type of modified starch,and its synthesis has broad development prospects in the pharmaceutical industry.In this study,solvent-free system to synthesize linoleic acid resistant starch esters with different degrees of substitution(DS).Under the condition of argon was injected into the reaction system,using corn resistant starch(RS3)and linoleic acid as raw materials catalyzed by Novozym 435.The synthesis conditions were futher optimized by response surface methodology on the basis of single factor experiment results.The effects of different reaction conditions on the degree of substitution were studied.The structural properties of different DS esterified starches were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),Fouriertransform infrared spectroscopy(FTIR)and Hydrogen-1nuclear magnetic resonance(~1H NMR).Physical and chemical properties of products of different DS also were determined.The highest DS product was utilized as drug carrier for sustained release in vitro release testing,and the drug release performance,drug release mechanism and probiotics properties were investigated.The results are as follows:1.Response surface methodology based on the results of single factor experiment was adopted to optimize the experimental conditions of the resistant starch linoleate synthesis.The optimal conditions for product with the highest degree of substitution(DS)of 0.04 were:Under the condition of argon was injected into the reaction system,4%of lipase dosage(based on resistant starch dry basis),pretreated resistant starch(RS3)/linoleic acid mass ratio of 1:7 during24.5 h of incubation at 65°C.2.The physical and chemical properties of linoleic acid-resistant starch esters with different DS were studied.It was found that with the increase of DS,the solubility,transparency and retrogradation of esterified products reduced gradually,swelling power increased gradually.A new band of carbonyl-C=O at 1720 cm~-11 was exhibited in Fourier transform infrared spectroscopy(FTIR)of esterified starch,indicating that the RS3 was successfully esterified.Then further analysised by Hydrogen-1 nuclear magnetic resonance(~1H NMR),the esterified starch successfully introduced long carbon chain linoleic acid group.Scanning electron microscopy(SEM)images showed that the crystalline structure of the RS3 was destroyed by the esterification reaction.Powder X-ray diffraction(XRD)showed that the crystallinity of the resistant starch decreased.3.Corn starch,RS3,DS 0.04 linoleic acid RS3 ester were used as carrier materials for5-fluorouracil(5-FU)drug sustained-release tablets respectively.The drug release performance and drug release mechanism were determined in simulated gastric fluid(SGF),simulated intestinal fluid(SIF)and simulated colonic fluid(SCF).The results showed that the drug release rate of esterified starch as carrier was lower than that of corn starch and RS3.Therefore,the esterified starch has a good sustained release property.The release mechanism indicated that the drug release curves of 5-FU linoleic acid RS3 ester sustained release tablets in three media were consistent with Higuchi drug release model.The drug release mechanism of 5-FU linoleic acid RS3 ester sustained-release tablets was synergistic effect of drug diffusion and dissolution.4.The 5-FU linoleic acid RS3 ester coated sustained release tablet can be delivered to the colon and achieve sustained release.The drug release curve accorded with the Higuchi drug release model,and the drug release mechanism was the dissolution release.5.The promoting growth and its metabolite short-chain fatty acids of RS3 and linoleic acid RS3 ester to Lactobacillus of intestinal microflora were studied by in vitro microbial culture experiments.The results showed that RS3 and linoleic acid RS3 ester can promote the growth of Lactobacillus and can be utilized by intestinal bacteria.From the analysis of its metabolites,it produced short-chain fatty acidacetic acid beneficial to human body. |
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