College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, Jiangsu, China.
College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, Jiangsu, China.
Int J Biol Macromol. 2016 Aug;89:518-26. doi: 10.1016/j.ijbiomac.2016.04.089. Epub 2016 May 6.
In this study, protocatechuic acid (PA) was grafted onto chitosan (CS) by a carbodiimide mediated cross-linking reaction. The structural characterization, physical property and antioxidant activity of PA grafted CS (PA-g-CS) was investigated. As results, three copolymers with different grafting ratios (61.64, 190.11 and 279.69mg PAE/g) were obtained by varying the molar ratios of reaction substrates. PA-g-CS showed the same UV absorption peaks as PA at 258 and 292nm. As compared to CS, PA-g-CS exhibited a decreased band at 1596cm(-1) and a new band at 1716cm(-1), suggesting the formation of amide and ester linkages between PA and CS. New proton signals at δ6.77-7⋅33ppm were observed on (1)H NMR spectrum of PA-g-CS, assigning to the methine protons of PA. Signals at δ 150.8-116.6 ppm on (13)C NMR spectrum of PA-g-CS was assigned to the aromatic ring carbon of PA moieties. All the structural information confirmed the successful grafting of PA onto CS. SEM observation showed CS had a smooth surface, while PA-g-CS had a rough surface. TGA revealed the thermal stability of PA-g-CS was lower than CS. Antioxidant activity assays further verified the reducing power and DDPH radical scavenging activity of PA-g-CS was much higher than CS.
在这项研究中，通过碳二亚胺介导的交联反应将原儿茶酸（PA）接枝到壳聚糖（CS）上。研究了 PA 接枝 CS（PA-g-CS）的结构特征、物理性质和抗氧化活性。结果，通过改变反应底物的摩尔比，得到了三种接枝率不同的共聚物（61.64、190.11 和 279.69mgPAE/g）。PA-g-CS 在 258 和 292nm 处表现出与 PA 相同的紫外吸收峰。与 CS 相比，PA-g-CS 在 1596cm(-1)处的带下降，在 1716cm(-1)处出现新带，表明 PA 和 CS 之间形成了酰胺和酯键。（1）在 PA-g-CS 的 H NMR 谱中观察到δ6.77-7 ⋅ 33ppm 的新质子信号，归属于 PA 的亚甲基质子。（13）在 PA-g-CS 的 C NMR 谱中，δ 150.8-116.6ppm 的信号被分配给 PA 部分的芳环碳原子。所有结构信息均证实了 PA 成功接枝到 CS 上。SEM 观察表明 CS 表面光滑，而 PA-g-CS 表面粗糙。TGA 表明 PA-g-CS 的热稳定性低于 CS。抗氧化活性测定进一步证实了 PA-g-CS 的还原能力和 DPPH 自由基清除活性均高于 CS。
