| Lutein is widely used in medicines and foods.As a natural antioxidant,it has a high ability to quench free radicals,and can decrease tissue damage caused by metabolism and light,protect macula lutea and reduce damage caused by visible spectrum.Appropriate intake of lutein can reduce the incidence of cataract.Lutein is also always used as a natural dye to improve the color of foods and drinks due to its good coloring ability.However,it has low water solubility and stability and is sensitive to high temperature,light,p H changes and oxygen,which limits the processing and industrial production of lutein.In chemical modification of lutein using the traditional method,the reaction conditions are harsh,which is not conducive to the stability of lutein,and sometimes may introduce excessive impurities.Therefore,it is very important to explore a rapid,efficient and simple method to modify lutein.In this project,the hydrophilicity and stability of lutein were modified using L-cysteine and polyethylene glycol monomethyl ether?MPEG?as raw materials.The main research contents and results are as follows:?1?L-cysteine-modified lutein?Cys-Lutein?was synthesized by thiol-ene click chemistry.Firstly,vinyl-terminated lutein was synthesized using lutein and acryloyl chloride,and then Cys-Lutein was synthesized by thiol-ene click chemistry of L-cysteine and vinyl-terminated lutein.The intermediates and end-products were characterized using fourier transform infrared spectroscopy?FT-IR?,and the stability of lutein during the reaction was investigated by UV-vis.The results showed that Cys-Lutein was synthesized successfully,and the conjugated carbon chains of lutein was not destroyed during the reaction.The self-assembled aqueous solution of Cys-Lutein was characterized using transmission electron microscopy?TEM?,and the self-assembled morphology of Cys-Lutein was observed,presenting that it formed spherical micelles in aqueous solution with an average particle size of 85 nm.However,L-cysteine did not significantly improve the stability of lutein.?2?Lutein-b-methoxy polyethyleneglycol block copolymer?Lutein-b-m PEG?-encapsulated lutein nanoemulsion was prepared by one-pot synthesis with lutein and polyethylene glycol monomethyl ether as raw materials.Through the click chemical reaction of m PEG containing terminal sulfhydryl group and lutein containing carbon-carbon double bond at the terminal group,Lutein-b-m PEG-encapsulated lutein nanoemulsion was synthesized.The synthesis of block copolymer and the loading of unreacted lutein were completed in one pot.The self-assembled morphology of Lutein-b-m PEG and the morphology of loaded lutein were observed by TEM.The results showed that the particle size of the spherical micelles formed by Lutein-b-m PEG self-assembly was about 27 nm without lutein loading,and about 35 nm after lutein loading.The critical micelle concentration of Lutein-b-m PEG aqueous solution was measured as 3.91×10-3mg/m L by the Du Noüy ring method.Encapsulation efficiency test showed that the encapsulation efficiency of lutein by Lutein-b-m PEG was 70%.The chemical stability of lutein under the protection by Lutin-b-m PEG was investigated,revealing that the retention rate of lutein was 74.3%after 30 day storage under dark at 20±5?.?3?Lutein-b-m PEG was synthesized using lutein and m PEG by the CDI coupling method.Firstly,m PEG was activated by CDI,and then reacted with lutein to synthesize Lutein-b-m PEG.By TEM characterization,it was found that in Lutein-b-m PEG aqueous solution,the hydrophobic lutein segments were surrounded by the hydrophilic m PEG segments,which increased its water solubility.The chemical stability test of Lutein-b-m PEG showed that the stability of lutein modified by the CDI coupling method was improved.The retention rate of lutein was over 70%after two-week storage at room temperature and exposed to with air. |
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