| Cyclodextrins(CD)with hydrophilic shells and hydrophobic internal cavities are often used as carrier material for a variety of insoluble compounds to improve their physicochemical properties and biological activities.In recent years,a large number of cyclodextrin derivatives have been designed and developed based on the structural characteristics of the cyclodextrins.These new functional materials have been widely applied in the fields of food additives,drug carriers and environmental protection,which have been research hotspots in constructing new materials.At present,the functional materials based on cyclodextrins mainly include cyclodextrin inclusion complexes,cyclodextrin covalent coupling compounds,polyrotane,and cyclodextrin polymers.Ferulic acid is a natural phenolic acid with a wide range of sources.It has many physiological functions,such as anti-oxidation,lowering blood lipids,bacteriostasis and anti-cancer.The low water solubility and poor stability lead to the low bioavailability and limited applications in the field of food and medicine.Three kinds of single-substituted cyclodextrin derivatives with different amino groups on C-6 positions were synthesized by chemical modification based on the structure of natural ?-cyclodextrin.Ferulic acid was used as model substrate to construct inclusion system,bonding system and polymer system based on ferulic acid and amino-cyclodextrins by physical embedding or chemical bonding,and the physicochemical properties such as water solubility,stability and in vitro biological activity were investigated.In addition,the in vitro bacteriostatic activity and related mechanism of ferulic acid/amino-cyclodextrin inclusion system were studied,which provided some theoretical reference and scientific basis for the development and utilization of cyclodextrin derivatives as new carrier materials for insoluble active substances.The main contents and conclusions of this paper are as follows:(1)Preparation,characterization and in vitro biological activity of ferulic acid/amino cyclodextrin inclusion complexes:three kinds of C-6 position monosubstituted cyclodextrin derivateives(NH-?-CD,EDA-?-CD and HDA-?-CD)with different alkyl amino side chains were prepared by structural modification of ?-cyclodextrin.The ferulic acid/amino-cyclodextrin inclusion complexes were prepared by lyophilization with the amino-cyclodextrins as host substances and ferulic acid as the guest molecule.Their structures were characterized and confirmed by infrared spectroscopy,nuclear magnetic resonance spectroscopy,scanning electron microscope and X-ray powder diffraction.The inclusion behavior between the host compounds and guest molecules were studied by Job curve method and phase solubility experiments.The results showed that all the amino-cyclodextrins complexed with ferulic acid via molar ratio of 1:1.Moreover,different alkylamino substitutions could affect the binding actions towards ferulic acid by changing the structures of cyclodextrin cavities,and the corresponding inclusion constants were as follows:KEDA-?-CD?KHDA-?-CD?KNH-?-CD.The ethylenediamine group at C-6 position,a kind of flexible alkyl side chain,was embedded into its own cyclodextrin cavity and produce favorable deformation to increase the inclusion with the guest molecules.The studies on the physicochemical properties and biological activity indicated that the water solubility,stability,in vitro antioxidant activity and anticancer activity of ferulic acid were significantly improved by complexing with amino-cyclodextrin.The results showed that amino modification on the C-6 positions of cyclodextrins can change the basicity and cavity structures of original cyclodextrin,thus affecting the inclusion complexation with the guest compounds.(2)Preparation,characterization and in vitro biological activity of ferulic acid-amino cyclodextrin conjugates:a series of ferulic acid-amino cyclodextrin conjugates(FA-NH-CD?FA-EDA-CD and FA-HDA-CD)were obtained by covalently linking ferulic acid with amino-cyclodextrins through carbodiimide-mediated coupling reactions.Their structures were characterized and confirmed by nuclear magnetic resonance spectroscopy,high-resolution mass spectrometry,X ray diffraction,scanning electron microscopy and so on.The self-assembly behaviors of the conjugates were studied.It was found that FA-NH-CD could form "head-tail" assemblies in water,while FA-EDA-CD and FA-HDA-CD could form self-included spatial structures due to the flexible alkyl chains at C-6 positions.Moreover,the anti-photodegradation properties,thermal stability and anti-hepatoma activities of the three conjugates were significantly enhanced than those of the free ferulic acid,and the water solubility of the FA-EDA-CD and FA-HDA-CD were also significantly increased.This study showed that the physicochemical properties and biological activities of ferulic acid could be effectively improved by constructing covalent coupling systems based on the amino-cyclodextrins and regulating the length of alkyl chains between ferulic acid and the amino-cyclodextrins.(3)Preparation,self-assembly and bioactivity of the polymers based on the amino cyclodextrins:the linear polymer PMMA was prepared through free radical copolymerization with methacrylic acid(MAA)and methoxypolyethylene glycol methacrylate(mPEGMA)as monomers.Then,the amino-cyclodextrins were introduced into the side chains of linear polymers by amide reactions to obtain three kinds of cyclodextrin-contained linear polymers PMMA-g-NH-CD,PMMA-g-EDA-CD and PMMA-g-HDA-CD,respectively.All the amino-cyclodextrin polymers can be self-assembled in water to form spherical micelles with uniform sizes and diameters at about 100 nm.The PMMA-g-HDA-CD containing longer alkyl chains in the side groups,could achieve efficient loading of ferulic acid by synergistic actions of hydrophobic segments and cyclodextrin cavities.Also,the polymer exhibited good pH responsiveness.The results of biological activities showed that PMMA-g-HDA-CD had certain biocompatibility and was mainly concentrated in the liver,exhibiting specific functions of liver targeting.(4)The in vitro bacteriostatic activity and the related mechanism of ferulic acid/amino-cyclodextrin inclusion complexes:The minimum inhibitory concentrations of ferulic acid/amino cyclodextrin inclusion complexes against five kinds of food-borne pathogenic bacteria(Staphylococcus aureus,Escherichia coli,listeria,Salmonella and Pseudomonas aeruginosa)were measured and the inclusion complex FA/NH-?-CD with the best bacteriostatic activity(MIC=0.012 mol/L)was selected as the research object.The growth curves of Staphylococcus aureus and Escherichia coli under different concentrations of FA/NH-?-CD were studied and characterized.The results showed that FA/NH-?-CD could significantly inhibit the proliferation of bacteria,prolong the lag period and reduce the maximum growth rate of bacteria.Series of biochemical experiments showed that the treatment with FA/NH-?-CD could evidently decrease the cell membrane potential,intracellular ATP content and destroy cell membrane integrity.In addition,the results of electron microscope observation indicated that FA/NH-?-CD could do damage to the normal physiological morphology of the bacteria,resulting in irreversible breakage such as deformation,depression and breakage of the bacteria.It could be preliminarily speculated that FA/NH-?-CD exerted its bacteriostatic effects by destroying cell membrane permeability and cell morphology of Staphylococcus aureus and Escherichia coli. |
PDF Full Text Request