Carboxymethyl chitosan (CMCS) is a water soluble derivate of chitosan, the unique natural cationic polysaccharide with versatile functions. However, the weak chain-breaking antioxidant capacity is still a shortage of CMCS in practical applications. To enhance the antioxidant capacity, CMCS was functionalized with chlorogenic acid (CA), a natural antioxidant compound, by a free radical grafting method in this study. The successful formation of CA-grafted CMCS (CA-CMCS) was confirmed by UV–Vis, FTIR, and ¹H NMR analyses, and CA-CMCS had a grafting ratio of 58.6 ± 1.5 mg CAE/g and a water-solubility of 21.0 ± 1.1 mg/mL. Due to CA presence, CA-CMCS showed different physicochemical and biological properties compared with CMCS. The crystallinity and thermal stability of CA-CMCS were lower than those of CMCS. More importantly, the DPPH and ABTS radical scavenging activities of CA-CMCS reached 92.4% and 99.4%, respectively, being much higher than those of CMCS. Also, better hydroxyl and superoxide radical scavenging activities as well as reducing power were obtained for CA-CMCS relative to CMCS. In addition, CA-CMCS revealed good stability, with its higher percentage in phenolic content and DPPH radical scavenging activity compared to CA. Our results suggest that CA-CMCS could be a promising antioxidant used in the fields of food and health care.

羧甲基壳聚糖（CMCS）是壳聚糖的水溶性衍生物，壳聚糖是一种独特的天然阳离子多糖，具有多种功能。然而，在实际应用中，弱的断链抗氧化剂能力仍然是CMCS的不足。为了提高抗氧化能力，本研究通过自由基接枝方法，用天然抗氧化剂绿原酸（CA）对CMCS进行了功能化。UV-Vis，FTIR和¹证实了CA接枝CMCS（CA-CMCS）的成功形成。1 H NMR分析和CA-CMCS的接枝率为58.6±1.5mg CAE / g，水溶性为21.0±1.1mg / mL。由于CA的存在，与CMCS相比，CA-CMCS表现出不同的理化和生物学特性。CA-CMCS的结晶度和热稳定性低于CMCS。更重要的是，CA-CMCS的DPPH和ABTS自由基清除活性分别达到92.4％和99.4％，远高于CMCS。而且，相对于CMCS，CA-CMCS获得了更好的羟基和超氧化物自由基清除活性以及还原能力。另外，与CA相比，CA-CMCS显示出良好的稳定性，其酚含量和DPPH自由基清除活性百分比更高。我们的结果表明，CA-CMCS可能是用于食品和保健领域的有希望的抗氧化剂。