Abstract
With the specialty of improving the water solubility of chitosan, quaternary ammonium salts have broadened the application of this polysaccharide in food, medicine and pesticides. To identify the effect of quaternary ammonium salts’ quantity, single quaternized chitosan N-phenmethyl-N,N-dimethyl chitosan (PDCS), double quaternized chitosan N-(1-pyridylmethyl-2-ylmethyl)-N,N-dimethyl chitosan (MP2MDCS), N-(1-pyridylmethyl-3-ylmethyl)-N,N-dimethyl chitosan (MP3MDCS), and N-(1-pyridylmethyl-4-ylmethyl)-N,N-dimethyl chitosan (MP4MDCS) were designed and synthesized successfully through chemical modification of chitosan. Besides, three kinds of antioxidant activities, including hydroxyl radicals, superoxide radicals, and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radicals were tested in vitro. As shown in this paper, the scavenging ability was ranking in order of MP3MDC > MP4MDCS > MP2MDCS > PDCS > chitosan at 1.6 mg/mL in all assays. All double quaternary ammonium salts were better than chitosan or the single quaternary ammonium salt. In addition, MP3MDCS could scavenge hydroxyl radicals totally at 1.6 mg/mL. MP2MDCS and MP4MDCS with more than 90% scavenging indices both had great scavenging ability on hydroxyl radicals or DPPH radicals. Furthermore, these data demonstrated that the increasing number of the positive charge would improve the antioxidant property of chitosan derivatives, and the N-pyridinium position would influence the scavenging radical ability.
Highlights
Free radicals, especially oxygen free radicals in one’s body, may damage the chemical structure of the organized cell and cause symptoms, such as ruptures of the main chain of the nucleic acid and protein peptide bond, membrane lipid peroxidation, enzyme inactivation, and cell apoptosis in certain pathological conditions [1,2,3,4,5]
The synthetic procedures of the quaternary ammonium salts chitosan are shown in Scheme 1
N-(2-pyridylmethy), N-(3-pyridylmethy), and N-(4-pyridylmethy) chitosan were synthesized based on the reaction between the primary amino group of chitosan and aldehyde group of pyridine carboxaldehyde following by the reduction with sodium borohydride
Summary
Especially oxygen free radicals in one’s body, may damage the chemical structure of the organized cell and cause symptoms, such as ruptures of the main chain of the nucleic acid and protein peptide bond, membrane lipid peroxidation, enzyme inactivation, and cell apoptosis in certain pathological conditions [1,2,3,4,5]. It was reported that pyridine chitosan derivatives could improve polysaccharide properties including solubility, physicochemical and biological properties, which could be applied in antimicrobial activity, sensor application, and biomedical application [27,28,29]. Double quaternary ammonium salts at different N-pyridinium position with a similar degree of substitution (DS) were investigated in this paper. In order to further study the influence of the positive charge and N-pyridinium position of quaternized chitosan derivatives on antioxidant activities, N-phenmethyl-N,N-dimethyl chitosan (PDCS), N-(1-pyridylmethyl-2-ylmethyl)-N,N-dimethyl chitosan (MP2MDCS), N-(1-pyridylmethyl-3-ylmethyl)N,N-dimethyl chitosan (MP3MDCS), and N-(1-pyridylmethyl-4-ylmethyl)-N,N-dimethyl chitosan (MP4MDCS) were synthesized successfully via N-pyridylmethyl chitosan in this paper, and the antioxidant activity was investigated systematically by the assessment of hydroxyl radicals’. FT-IR, 1 H-NMR, and the elemental analyses characterized the chemical structure of the chitosan derivatives
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