Synthesis And Functional Properties Of Alkylated Pectin And Its Application As Drug Carrier

Pectin is an important natural anionic polysaccharide,this polysaccharide is known as gelling agent,thickener,texturizer,emulsifier and stabilizer in food industry,pharmaceutical industry and cosmetic applications.However,functionality of pectin sometimes needs to be strengthened or altered to satisfy the demand of market for innovative and functional products.So there has been an increased interest in modification of pectins.This paper describes studies on the alkylation modification of pectin on the one hand,and the change of structure and functional properties of modified pectin were evaluated by various indicators such as Fourier Transform Infrared Spectra,1H-NMR,intrinsic viscosity,molecular weight,rheological properties and emulsifying properties.We have also carried out studies on microwave-assisted synthesis of alkylated pectin,the effect of the reaction conditions was investigated.On the other hand,we made the modifid pectin ancapsulate BSA drug,and conduct the test of drug release behavior.The conclusion are as follows:1、Pectins were alkylated with alkyl chain of various lengths(hexyl,dodecyl or octadecyl)at different degrees of substitution(0.69,2.43 or 3.60)by reaction of TBA-pectin with alkyl bromide in this study.Their structures were characterized by GC,FTIR and ’H-NMR,which confirmed the formation of ester linkages between hydrophobic alkylsegment and carboxyl group of galacturonic acid.Alkylated pectins showed higher apparent viscosities but lower intrinsic viscosities than the original one.The higher apparent viscosities may be due to intermolecular association of hydrophobic segments in the molecule.The lower intrinsic viscosities would be ascribed to more compact conformation.In addition,the modified pectins showed an enhancement of emulsifying properties.These properties were significantly influenced by the degree of substitution and alkyl chain length.2、By using a microwave radiation method for synthesis of alkylated pectin,the influence of microwave power and reaction time on the degree of substitution were studied.The microwave radiation produced a higher yield of alkylated pectin,with a shorter processing time.Their structures were characterized by GC,FTIR and 1H-NMR,which confirmed microwave radiation successfully applied in the preparation of alkylated pectin,and the two kinds of alkylated pectin have similar physicochemical properties.By measuring the apparent viscosities and emulsifying properties indicated microwave-assisted alkylated pectin have higher apparent viscosities,EC and ES compared with original pectin,and these properties increased with the increase of DS and alkyl chain length,the change in accord with the alkylated pectin without microwave radiation.3.Alkylated pectin prepared by chemical covalent binding of C12 alkyl chains onto the polysaccharide backbone via ester functions,can form strong hydrogels crosslinking with Ca2+.These hydrogels have been exploited to prepare drug-lodaed microsphere(MS).SEM analysis indicated C12-alkylated pectin MS appeared a smooth surface and close texture.Drug-polymer interactions were studied by Differential Scanning Calorimetry,the results show that there exist interactions between BSA and pectin during MS preparaton.BSA encapsulation yield of C12-alkylated pectin MS significantly higher than non-modified pectin MS,the high BSA retention in C12-alkylated pectin MS is thus likely to result from the existence of hydrophobic microdomains inside the hydrogel,which interact with the hydrophobic parts of the protein.Release tests indicated C12-alkylated pectin MS completely avoiding drug release in simulated gastric ambient,and reaching 100%release in the colonic simulated medium within less than 12 h,thus C12-alkylated pectins are potential carriers for colon-specific drug deliveries.