壳聚糖与柠檬醛缩合反应产席夫碱及其抗菌活性

通过壳聚糖与柠檬醛在超声波振荡下反应制备了壳聚糖缩柠檬醛席夫碱。采用L9（33）]正交实验探讨了反应时间、反应温度及反应物配比对壳聚糖席夫碱缩合率和取代度的影响。最佳条件为：反应物配比n（壳聚糖）∶n（柠檬醛）=1∶6，反应温度40～50 ℃，反应时间10 h，壳聚糖席夫碱的缩合率可达86%，取代度为0.82。红外光谱和X射线衍射光谱结果表明产物具有壳聚糖席夫碱的结构特征。对大肠杆菌、金黄色葡萄球菌和黑曲霉的抗菌实验表明，该产物对大肠杆菌、金黄色葡萄球菌和黑曲霉的最低抑菌浓度分别为1 g/L、1 g/L和5 g/L，其抗菌活性随浓度的增加而增加，且优于壳聚糖。

Synthesis and antibacterial activity of schiff base from chitosan and citral

Although chitosan is a biocompatible, biodegradable and nontoxic polymer, its application suffers severe limitations because it is insoluble in neutral or alkaline media. This paper reports the synthese of Schiff base of chitosan by the reaction of chitosan with citral assisted with high-intensity ultrasound. Effect of the ratio of chitosan to citral. reaction time and temperature on the yield and the degree of substitution has been investigated. The optimal conditions were found to be with reaction temperature of 40-50 ℃, the ratio of chitosan to citral of 1:6 and 10 h of reaction time. The maximum yield was achieved to 86% and the degree of substitution was 0.82 under the optimized reaction conditions. The structure of the Schiff base was characterized by FTIR and XRD spectroscopy, which confirmed that the amino groups in chitosan have been reacted with citral to form the Schiff base. The antibacterial activities of the Schiff base were investigated by assessing the inhibitory rates of Escherichia coil, Staphylococcus aureus and Aspergillus niger. The MICs of Schiff base against E. coli, S. aureus and A. niger were found as 1g/L, 1g/L and 5g/L, respectively. The antibacterial activity of the Schiff base increases with the increase in bacterial concentration and is stronger than that of chitosan.