Preparation O Chitosan Dervatives By Schiff Base And Antimicrobial Activity Of The Dervatives

Particular biological properties are in the possession of chitosan, then it is insoluble in water. The reactive products that chitosan ester and quaternary ammonium salts of chitosan not only improve the solubility of chitosan, and contribute to enhancing antimicrobial activity. The article prepares four kinds of chitosan derivatives which contain chitosan ester(ABCTSE), O-carboxymethyl chitosan(OCMC), N-metoxybenzenemethyl quaternary ammonium salt of chitosan (NM-chitosan) and N-hydroxybenzenemethyl quaternary ammonium salt of chitosan (NH-chitosan), the products can reveal the particular activity of chitosan and substitutional materials, and The synthesized compounds can also exhibit excellent solubility and antimicrobial properties.The article researches the process of preparation of chitosan derivatives according to chemical modification and the applications of bacteriostasis. The ratio of chitosan to substitutional materials and the reaction time tend to be certain, and get the optimal temperature from the change of degrees of substitution; chitosan derivatives exhibit an excellent solubility in the water and organic solvents at room temperature; The structures and properties of the derivatives are characterized by FT-IR, 1H NMR, elemental analysis and thermal analysis, the degrees of substitution are got by the results of elemental analysis and the new formula, and the degrees of quaternization are got by the way of ICl drop, also the structure of ABCTSE is characterized by 13C NMR; The article researchs the effect of concentration on the antibacterial activity of chitosan and chitosan derivatives against Staphylococcus aureus and Aspergillus niger, and obtain the curve of inhibition rate, then text inhibitory effect of chitosan and derivatives on growth of Staphylococcus aureus and Aspergillus niger.1. Preparation, characterization and antimicrobial activity of OH-substitution chitosan derivativesThe obtained Schiff base reacts with acyl chloride to get N-benzoyl-O- aminobenzoyl chitosan ester(BABCTSE), removing the groups of amino protection to get the final product (ABCTSE); The structures of the derivatives are characterized by FT-IR, 1H NMR,13C NMR and elemental analysis; The elemental analysis results indicated that the biggist degree of substitution is 40.4% at 40℃; and the product exhibits better solubility in organic solvents than that of chitosan; TG and DTG results show that thermal stability of the derivatives is lower than that of chitosan. Schiff base of chitosan reacts with chloroactic acid, removing the group of amino protection to get OCMC, The obtained chitosan derivative is characterized by FT-IR, 1HNMR and elemental analysis;The chitosan derivative reveals excellent solubility and thermal stability in comparison with chitosan, and it has the biggist degree of substitution of 82.6% at 60℃.The inhibition rate of ABCTSE and OCMC on Staphylococcus aureus and Aspergillus niger tends to be higher than that of chitosan, and the minimum inhibitory concentrations(MICs)of chitosan derivatives on Staphylococcus aureus are 0.1% and 0.5%, while 0.25% and 1% on Aspergillus niger. Inhibitory effect of ABCTSE shows stronger than that of OCMC on growth of Staphylococcus aureus, but weaker on growth of Aspergillus niger.2. Preparation, characterization and antimicrobial activity of quaternary ammonium salts of chitosan,Schiff base of chitosan obtained by the reaction of chitosan and aromatic aldehyde reacted with methyl iodide to get soluble quaternary ammonium salts of chitosan. and the chitosan derivatives are characterized by FT-IR, 1H NMR and elemental analysis, the results shows that there is small difference between degrees of quaternization(DQ) and degrees of substitution(DS); Chitosan and chitosan derivatives are dissolved in different organic solvents to measure the solubility at room temperature, and the two new kinds of quaternary ammonium salts of chitosan appear to be good of solubility in the solvents; Two products reveal obvious difference in comparison with chitosan at the term of thermal stability according to the results of TG and DTG, NM-chitosan possesses preferable thermal stability, and NH-chitosan is clied to be poor.It is found that the antimicrobial activity of quaternary ammonium salts are stronger than that of chitosan. The minimum inhibitory concentrations(MICs)of NH-chitosan on Staphylococcus aureus and Aspergillus niger are respective 0.1% and 0.25%, and which of NM-chitosan are 0.5%. The data of growth experiment shows that the growth curves of the microbe with NH-chitosan and NM-chitosan seem to be lower, which confirm the products improve the antimicrobial activity of chitosan in some extent and expands the antimicrobial spectrum.