Structural characteristics and enhanced biological activities of partially degraded arabinogalactan from larch sawdust

Larch arabinogalactan (AG), extracted from Larix gmelinii sawdust, was depolymerized by H2O2 oxidation and purified by gel column to yield a novel degraded fraction (AGD2). The structural analysis indicated AGD2 had lower arabinose content and molecular weight compared with AG, in which the ratio of galactose and arabinose was changed from 7:3 to 16:1, the molecular weight was decreased from 50.2 kDa to 3.7 kDa, and the chain conformation spread from highly branched structure to flexible strand. It was one kind of beta-D-(1 -> 3)-galactan with fewer beta-D-(1 -> 6)-Galp side branches at O-6 position. Further, the results of the Gal-3 binding and immunomodulatory assay suggested that the unbinding force of AGD2 onto Gal-3 was as twice as AG to be 76 +/- 11 pN at the loading rate of 0.15 mu m/s. It could better promote the secretion of pro-inflammatory cytokines (TNF-alpha, IL-6 and IL-1 beta) than AG in a dose-dependent manner. (C) 2021 Elsevier B.V. All rights reserved.