Structural characterization and anti-inflammatory activities of anti-complementary polysaccharides from Rhododendron principis.

Abstract

Rhododendron principis leaves have been used as "Dama", a Traditional Tibetan Medicine for treating inflammatory diseases. R. principis crude polysaccharides (CZND) with anti-complementary activity demonstrated promising anti-inflammatory effects on acute lung injury (ALI) induced by lipopolysaccharide (LPS). CZND significantly decreased the levels of TNF-α and IL-6 in both serum and BALF (blood and bronchoalveolar lavage fluid) in LPS-induced ALI mice by intragastric administration (100 mg/kg). A heteropolysaccharide, ZNDHP, was obtained from CZND with successive anti-complementary activity-guided separation. ZNDHP was characterized as a branched neutral polysaccharide with a backbone composed of →2)-β-Glcp-(1→, →2,6)-α-Glcp-(1→, →6,3)-β-Galp-(1→, →2,6)-α-Galp-(1→, →6,2)-β-Glcp-(1→, →4)-α-Glcp-(1→, →5)-β-Araf-(1→, →3,5)-α-Araf-(1→, and →4,6)-β-Manp-(1→, and the backbone structure was further confirmed by partial acid hydrolysis. In addition to anti-complementary and antioxidant activities, ZNDHP exhibited potent anti-inflammatory activity by significantly inhibiting the secretion of NO, TNF-α, IL-6, and IL-1β of LPS treated RAW264.7 cells. However, all of these activities decreased greatly after partially hydrolyzing, indicating the importance of the multi-branched structure for its bioactivity. Therefore, ZNDHP might be an important component of R. principis for treating inflammation.