Structural characterization and antioxidant activities of one neutral polysaccharide and three acid polysaccharides from the roots of Arctium lappa L.: A comparison

In this work, we comparatively analyzed the structure and antioxidant activities of different polysaccharide fractions from Arctium lappa L. A total of four water-soluble polysaccharide fractions (ALP-1, ALP-2, ALP-3 and ALP-4) were obtained from the roots of Arctium lappa L. They differed in monosaccharide composition, molecular weight and linkage mode. ALP-1 and ALP-2 mainly consisted of fructose, with average molecular weights of 2.676 x 10(3) and 2.503 x 10(4) g/mol, respectively. ALP-3 and ALP-4 were mainly composed of fructose, arabinose and galactose, with average molecular weights of 9.709 x 10(4) and 6.790 x 10(4) g/mol, respectively. Furthermore, Fourier transform infrared spectrometry, methylation analysis and nuclear magnetic resonance spectroscopy suggested that the main polysaccharide ALP-1 had a linear chain of (1 -> 2)-linked beta-D-Fructofuranosyl backbone (n approximate to 15) linked to a terminal (1 -> 2)-linked alpha-D-Glucopyranosyl at the non-reducing end. All five polysaccharides displayed high antioxidant ability, especially ALP-4 in H2O2-induced HepG2 cell model and ALP-1 in metronidazole [MET]-induced zebrafish model. These findings provided comparative information on the structure and biological activity of different burdock polysaccharides and highlighted their potential as antioxidants in functional foods. (C) 2021 Published by Elsevier B.V.