Structural Elucidation and Immune-enhancing Activity of an Arabinogalactan from Flowers of Carthamus Tinctorius L

Previous studies showed that polysaccharides from flowers of Carthamus tinctorius L. had immunomodulating activities. However, their structures were little known. Here, an arabinogalactan, named as HH1-1 with a relative molecular weight of 70.9 kDa, was isolated from flowers of Carthamus tinctorius L. by hot water extraction, followed by purification of a DEAE-Cellulose 32 column and a Sephacryl S-200HR column, subsequently. The structure of HH1-1 was evaluated to have a backbone of 1,6-linked Galp branched at C-3 by side chain of 1,3-linked Galp, with sub-branches attached at its C-3 position. The branches mainly contained 1,5-linked, 1,3,5 linked, terminal arabinose and terminal galactose. Biological activity assays showed that this polysaccharide had immune-enhancing activity by multiple ways, including promoting immune responses by activation of NF-κB signaling and increasing TNF-α, IL-1β and iNOS expressions in lymphocytes and macrophages.