| For the disadvantage of L-ascorbic acid (vitamin C, VC) that it is easily to be oxidized during the treatment and process, two new kinds of derivative---chitosan ascorbate and 2-O-chitosan-ascorbic acid were studied. For the oxalic acid is formed in high yield from VC in gastric juice, the chitosan-VC micro sphere was prepared and then was microencapsulated into ethylic cellulose (EC).By designing appropriate experiments, the conditions of synthesizing chitosan-ascorbic acid complex were studied. The analysis of VC content, output rate, solubility helped us to get the optimal condition of synthesizing. The 13C NMR assignments, infrared spectrum permitted the identification of the structure of these complex. After the function test, it is found that chitosan ascorbate and 2-O-chitosan-ascorbic acid have good water-soluable ability. The existent of chitosan macro-molecular structure prevents the oxygen from destroying VC, so VC is to be protected. Since VC has good anti-bacteria ability and absorbability to serum lipoprotein, it enhances the same ability of chitosan.At the same time, L-ascorbic acid, used as a model drug, was efficiently entrapped within chitosan micro spheres using reversed-phase emulsion cross linking reaction and then was microencapsulated into ethylic cellulose. The morphology and release properties of microcapsules were tested. The influential factors of preparation conditions included molecular weight of chitosan, ratio of water and oil, reaction time, concentration of cross linker were discussed. The results of in vitro release studies show that the microcapsules prepared in this article are stable in gastric juice and can realize sustained release in intestine juice.
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