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.