| Summary: | 碩士 === 靜宜大學 === 食品營養學系 === 104 === Low–molecular-weight chitosan and chitooligosaccharides are a non-toxic, biocompatible and biodegradable nature biopolymer, and have a variety of biological activities. The purpose of this study was to investigate the molecular size, antioxidant capacity and selected enzyme inhibitory activities of a commercial chitooligosaccharides preparation. The molecular mass of the chitooligosaccharides preparation was less than 10 kDa, and most in the range of 10 to 3 kDa, as estimated by ultrafiltration with different molecular weight cutoff membranes. However, it also consisted of some small size oligomers with chain length larger than 3, as analyzed by thin-layer chromatography.
Antioxidant activities of the chitooligosaccharides preparation were evaluated with models of scavenging effect on ABTS, superoxide anion, hydroxyl and oxygen radicals. The trolox equivent scavenging values of the chitooligosaccharides toward ABTS, superoxide anion and oxygen radicals were 7.42 ± 0.17 mg trolox/ g COS，53.74 ± 0.002
mg trolox/g COS and 1140 ± 42.43 μmol trolox/ g COS, respectively. The half –effective concentration (EC50) of the chitoolgosaccharides preparation toward hydroxyl radicals was 412.87 ± 0.106 μg/mL.
Reducing power of the chitooliosaccharides preparation was evaluated by a ferri-ferrocyanide and ferric chloride model. Its trolox and ascorbic acid equivalent reducing power values were 151.49 ± 0.015 mg trolox/g COS and 8.97 ± 0.011 mg ascorbic acid/g COS, respectively.
Results of evaluation of selected enzyme inhibitory activities showed that the chitooligosaccharides preparation had inhibitory activities toward acetylcholinesterase and α-amylase. Its half-inhibitory concentration (IC50) values toward acetylcholinesterase and α-amylase were 18.82 ± 0.79 and 6.73 ± 0.28 mg/mL, respectively. Inhibitory kinetic analysis indicated that the chitooligosaccharides preparation was a noncompetitive inhibitor against α-amylase.
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