tailieunhanh - Structure identification of chitosan oligomers during the depolymerization process by hydrogen peroxide

Chitosan oligomers were prepared by oxidative degradation of chitosan (with hydrogen peroxide) under microwave irradiation. This is convenient, friendly and effective method to prepare chitosan oligomers. By 1 H-NMR, IR spectrum, the structure of the products was identified and keeps the same as of chitosan. By LC-MS analysis, it proved that chitosan was decomposed to five fractions, the smallest one about D- glucosamine 3 units (at least). | Journal of Chemistry Vol. 45 6A P. 334 - 338 2007 STRUCTURE IDENTIFICATION OF CHITOSAN OLIGOMERS DURING THE DEPOLYMERIZATION PROCESS BY HYDROGEN PEROXIDE Received 15 October 2007 NGUyEN THI DONG DO TRUONG THIEN Institute of Chemistry Vietnamese Academy of Science and Technology SUMMARy Chitosan oligomers were prepared by oxidative degradation of chitosan with hydrogen peroxide under microwave irradiation. This is convenient friendly and effective method to prepare chitosan oligomers. By 1H-NMR IR spectrum the structure of the products was identified and keeps the same as of chitosan. By LC-MS analysis it proved that chitosan was decomposed to five fractions the smallest one about D-glucosamine 3 units at least . I - INTRODUCTION Chitosan oligomers a degradation product of chitosan have some special physiological activities 2 differently from initial chitosan such as binding lipid affecting the mitogenic responses and restraining the growth of tumors 3 5 . It was widely used in pharmaceutical functional foods cosmetics and so on recently. Chitosan oligomers can be obtained either by the enzymatic depolymerization or by the acidic depolymerization. In addition chitosan oligomers are obtained by the oxidative depolymerization with oxidants. Thus there are some reports on the depolymerization mechanism of chitosan on the preparation of oligoglucosamine by treatment chitosan with H2O2 because it is handily easily available and environmental friendly. Otherwise microwave irradiation using the commercial domestic microwave oven has received increasing interest in organic synthesis due to remarkable enhancements of the rates of some organic reaction and significant effects over conventional reaction 1 . In this paper we have hydrolyzed chitosan by H2O2 under microwave irradiation to obtain the water-soluble oligoglucosamine and studied their structure identification by 1H-NMR and IR spectra. II - EXPERIMENTAL 1. Materials and apparatus p-chitin was extracted from squid pen

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