The Synthesis Of Mangiferin Ester Catalyzed By Immobilized Lipase

Glocosides widely exist in nature, such as tyrosine glocosides in larvas and imagoes, cerebrosides in nervous systerms, vitamin glucosides in mammals, precursor of compounds with aromatic odor in plants and so on. So far, glucosides have been applied in surfactant industry. Many glucosides possess special pharmacological properties. For example, amygdalins can be used to relieve cough, liquiritins can inhibit ulceration, gastrodines have the ability to relieve migraine and quercetin glucosides can be used for anti-tumor and anti-oxidant. Therefore, glycosides have certain potential for pharmaceuticals. However, there still exist certain limits of glucosides in clinical application due to their ability of water-solubility and lipid-solubility. It has reported that the introduction of the acyl donor can enhance the lipid-solubility of glucosides. Mangiferin has difficulty in running through the blood-brain barrier (BBB) due to its low lipid-solubility. To improve the lipid-solubility of mangiferin, synthesis of mangiferin ester using fatty acid ester and mangiferin as substrates were investigated.There exit many disadvantages in the synthesis of glucosides through chemical methods like harsh reaction conditions, tending to carbonize and lactonize, poor regioselectivity, difficulty of controlling the number of ester bonds, products containing a variety of by-products, introduction of toxic by-products and difficult purification of products.In recent years, enzymatic synthesis has been used in the synthesis of glucoside esters as a "green method". Mangiferin esters were synthesized through using lipases as catalytics due to their efficiency, specificity, mild reaction conditions and low pollution. Meanwhile, enzyme source, reaction medium and substrate were screened as well as reaction conditions were optimized. The optimum conditions were:PCL as catalyst, DMSO as solvent vinyl acetate as acyl donor,45℃as optimum temperature, 7.0 as optimum pH,0.33as optimum water activity.Immobilization technology has been widely used in enzymology, including adsorption, encapsulation, covalentce and cross-linking. The stability and reusability of immobilized enzyme are obviously prior to free enzyme. Adsorption was used to immobilize PCL on 6 different immobilized materals because of its simple operation and abundant materials. After comparasion of these 6 materials, aluminum phosphate (AIPO) was selected as the optimum immobilized materal to investigate the prosperities of immobilized PCL.Mesoporous materials (pore diameter ranging from 2.0 to 50.0 nm) has been widely used in nano-reactor, adsorbent, properties of nano-materials and photovoltaic properilities of microelectronics and optical materials due to their high specific surface area, high porosity, single distribution of pore diameter as well as wide range of size control (1.3-30nm). Mesoporous aluminum phosphate material with appropriate pore diameter and certain acid or base sites was used to prepare immobilized PCL. After comparison between immobilized PCL with AIPO and free PCL, the activity of AIPO-PCL was a little higher. After optimizing the reaction conditions, P/Al ratio (1:1), temperature (45℃), pH (8.0), water activity (0.33) and ionic strength (1mol/L) were screened as the optimum condition. Besides, immobilized PCL still remained high activity after five circles.