Research On O-carboxymethyl Chitosan Grafted Azo Pigment:Preparation And Anti-reductive Ability

In the 21 st century,the synthetic pigments were widely used in many fields due to their advantages such as low price,easy to produce,stable structure and rich color.Synthesized edible pigments are mostly azo-compounds which can be degraded and metabolized to aromatic amines in liver or by the gut microflora.Aromatic anilines and naphthylamine are toxic to body.So,it is of great significance to daily life of human to find a way to modify edible azo pigment in some degree,and decrease toxicity by reducing their degradation in body.O-Carboxymethyl chitosan(O-CMCTS)is an amphiprotic ether derivative of CTS,containing carboxyl and amino groups.It has received considerable attention for biomedical application because of its special properties of nontoxicity,biodegradability,biocompatibility,and antifungal activity.Furthermore,O-carboxymethyl chitosan is difficult to be absorbed and degraded due to its high molecular weight.We design the following two routes to improve properties of azo pigment:1.Phenolic hydroxyl in azo pigment deprotonates into negative oxygen ions,then reacts with epichlorohydrin and generates azo phenolic pigment intermediates by nucleophilic substitution reactions under basic conndition.Glycidyl in azo phenolic pigment intermediates ruptures after reacting with amino groups in O-carboxymethyl.Thus,O-carboxymethyl chitosan was grafted with azo pigment.Sunset yellow,carmine and amaranth were used to synthesize grafted O-carboxymethyl chitosan by the above ways.Their structures were confirmed by IR and 1H NMR.In the citric acid buffer solution of pH=6.0,the grafted products were reduced by NADH.Reduction rate were determined by UV.Though the comparison,the anti-reductive ability of grafted azo dye can be studied.2.Carboxymethyl chitosan iron(Ⅲ)complexes with azo dyes were prepared by homogeneous method,using O-carboxymethyl chitosan(O-CMCTS)and azo pigments as ligands,and ions(Ⅲ)as the ligand ion under the neutral condition of pH=7.0.Sunset yellow and carmine were used to synthesize two O-carboxymethyl chitosan complex products by the above ways.The iron content of complexs quantify by ICP,and their structures were confirmed by IR.In the citric acid buffer solution of pH=6.0,the two kinds of complex products were reduced by NADH.Reduction rates were determined by UV.Though the comparison,the anti-reductive ability of complex products can be studied.