Structural characteristics and antioxidant activities of different families of 4-acetamido-TEMPO-oxidised curdlan.
Regioselective oxidation was applied to commercial curdlan for the preparation of its water-soluble derivatives with improved antioxidant activities, using a 4-acetamido-2,2, 6,6-tetramethylpiperidine-1-oxyl radical/NaClO/NaClO2 system at pH 4.8 and 40°C. The structural features, molecular properties, and chain conformations of the oxidised curdlans were determined using Fourier transform (FT) infrared and FT Raman spectroscopy, carbon nuclear magnetic resonance, X-ray diffraction, and size-exclusion chromatography with multi-angle laser-light scattering analyses. The C6 primary hydroxyls of curdlan were successfully oxidised into carboxylate groups with less depolymerization, and no aldehyde groups were formed during oxidation. The crystalline region of curdlan was destroyed after oxidation. The oxidised curdlans formed random coils in aqueous solution, and the chain became more flexible and expanded with increasing carboxylate contents from 2.07mmol/g to 4.87mmol/g. The high polyglucuronic acid derivative (Cur-24) showed the best antioxidant activity in TEAC and FRAP assays, thus it could be explored as novel potential antioxidants for dietary and therapeutic applications.
School of Food & Biological Engineering, Jiangsu University, Zhenjiang 212013, China; Physical Processing of Agricultural Products Key Lab of Jiangsu Province, Zhenjiang 212013, Jiangsu, China. Electronic address: jkyan_27@163.com.
Jing-Kun
JK
Yan
Hai-Le
HL
Ma
Pan-Fu
PF
Cai
He-Nan
HN
Zhang
Qi
Q
Zhang
Nan-Zi
NZ
Hu
Xiao-Bo
XB
Feng
Jian-Yong
JY
Wu
D000975:Antioxidants / Q000737:chemistry*; D002236:Carbohydrate Conformation; D003497:Cyclic N-Oxides / Q000737:chemistry*; D005810:Multigene Family; D010084:Oxidation-Reduction; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction; D047071:beta-Glucans / Q000737:chemistry*
D000975:Antioxidants; D003497:Cyclic N-Oxides; D047071:beta-Glucans; C038459:curdlan; C003959:TEMPO
4-Acetamido-TEMPO; Antioxidation; Chain conformation; Curdlan; Oxidation