Characterization of a polysaccharide from the medicinal lichen, Usnea longissima, and its immunostimulating effect in vivo

A polysaccharide, CSL-0.1, was isolated from the medicinal lichen, Usnea longissima . CSL-0.1 was a neutral rhamnose-containing glucogalactomannan with a molecular weight of 7.86 × 10 4 Da. The polysaccharide had a core mannan structure with (1 → 6)-α- d -Man p units as the main chain and was substituted at the O -2 positions with side chains containing (1 → 2)-α- d -Man p residue, [3)-α-Glc p (1 → 4)-α-Glc p (1→] and 6- O -substituted β- d -Gal f units. 2- O - and 2,3-di- O -substituted Rha p units. The effects of CSL-0.1 on intestinal immunity and antioxidant activity were evaluated. CSL-0.1 increased the spleen and thymus indices in a dose-dependent manner and conferred immunomodulation on reversing the Th1/Th2-related cytokine imbalance in cyclophosphamide (CP)-induced immunosuppressed mice. CSL-0.1 could also enhance the levels of secretory immunoglobulin A in CP-injected mice. Additionally, the antioxidant levels in the liver and intestine of the mice were increased 20%–50% after intragastric injection by CSL-0.1.