Functionalization of carboxymethyl chitosan with chlorogenic acid: preparation, characterization, and antioxidant capaci
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ORIGINAL RESEARCH
Functionalization of carboxymethyl chitosan with chlorogenic acid: preparation, characterization, and antioxidant capacity Chaohong Zhang1 · Xueqing Yu1 · Yujia Diao1 · Yingjun Jing1 Received: 7 June 2020 / Accepted: 3 October 2020 © Iran Polymer and Petrochemical Institute 2020
Abstract 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. Keywords Antioxidant capacity · Carboxymethyl chitosan · Chlorogenic acid · Graft
Introduction Free radicals, especially reactive oxygen species (ROS), are continuously generated in the human body by normal metabolic processes. The free radicals at low levels have beneficial effects on cellular responses and immune functions, and the human body has various mechanisms to balance the formation of free radicals [1]. However, the overload of free radicals occasionally occurs in cells, resulting in severe damage to biomolecules, including lipids, proteins, and DNA, and subsequent various diseases such as aging, cancer, and cardiovascular disease [2]. To eliminate the excessive free radicals, intake of dietary antioxidants has been proposed, and positive effects are proved [3]. Among various natural compounds, chitosan is considered as a * Xueqing Yu [email protected] * Yingjun Jing [email protected] 1
School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China
suitable candidate for dietary antioxidant supplements due to its good biocompatibility and health effects on the human body [4]. However, chitosan is insoluble in water and has weak hydrogen-donating ability, which would limit its practical applications. Fortunately, chitosan has numerous active hydroxyl and amino groups [5], which can be easily chemically modified.
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