Experimental Study On Synthesis Of Laminine And Its Separation And Purification

Laminine is a natural marine medicine extracted from kelp,which has good blood pressure lowering activity and cholesterol-lowering effect.This advantage makes laminine have a good application prospect.Due to the extremely low content in kelp,laminarin is currently mainly prepared by chemical synthesis.However,the existing synthetic route has many problems such as high toxicity of raw materials and low yield.In this study,lysine hydrochloride（Lys·HCl）was used as the starting material and dimethyl carbonate（DMC）with low toxicity and environmental protection was used as the methylation reagent to explore the green and efficient synthesis of laminine under high pressure conditions.And study its separation and purification process to establish a stable and reliable route to promote the industrialization of laminine.Firstly,the synthesis of lysine metal chelate was studied,and nickel was selected as the best metal ion to protect lysineα-NH₂.The effects of reaction temperature,p H,time and reaction material ratio on the chelating effect of nickel lysine were explored,and the optimal conditions were determined as:n_{（Ni Cl2·6H2O）}:n_{（Lys·HCl）}=2:1.2,p H=10,the reaction was carried out at 60°C for 2 h,and under this condition,the yield of nickel lysine was90.51%.In order to realize the one-pot synthesis of laminine,this study also conducted research on the synthesis of nickel lysine chelate in organic phase methanol,and explored the optimal conditions from the aspects of catalyst type,catalyst amount,reaction temperature and time,etc.The optimal conditions for synthesizing lysine chelate in methanol were determined as follows:using anhydrous sodium carbonate as catalyst,n_{（Ni Cl2·6H2O）}:n_{（Lys·HCl）}=2:1.5,react at 55℃for 4 h,and then Under this condition,the yield of nickel lysine was 76.20%.On the above basis,using dimethyl carbonate as the methylating reagent,the methylation experiment was carried out on the free amino group on the lysine nickel chelate in a high pressure reactor.The reaction solvent,catalyst,material ratio,reaction temperature and time were explored and optimized,and the reaction conditions were determined as follows:methanol as the reaction solvent,sodium carbonate as the catalyst,n_（Lys-Ni）:n_（DMC）=1:15,reacted at 135°C for 10 h,the yield was 61.54%.The one-pot synthesis conditions of laminine were optimized by response surface methodology（RSM）,and the optimal reaction conditions were determined as:n_{（Lys·HCl）}:n_（DMC）=1:7,reaction temperature140℃,reaction time 10 h,the yield was 38.26%.Through column chromatography,a light yellow solid product was finally obtained.The physical properties of the product were explored,and the mass spectrometry and nuclear magnetic analysis showed that the obtained product was consistent with the expected structure of laminine.A variety of detection methods for laminarin content were studied,and thin-layer chromatography was used for qualitative detection of reaction products,and a method for determination of laminarin content by Rays salt colorimetric method was established,which could accurately determine the content of laminarin.The column chromatography separation method and ion exchange resin separation method were experimentally studied,and the conditions for ion exchange resin separation of laminine were optimized.The initial concentration was 4 g·L^-1,p H=4.5,the adsorption time was 4 h,and the adsorption amount was 102 mg·g^-1.Finally,0.5 mol·L^-1 ammonia water was used for elution,and the eluate was collected,and the resolution rate reached 92%.Compared with the column chromatography separation method,the ion exchange resin method is more suitable for industrial production and is conducive to promoting the industrialization process of laminine.