A sulfated galactan LP-G2 was isolated and purified from red alga, Pyropia haitanensis. It was a branched polysaccharide with average molecular weight about 8381 Da, composed of Gal, Glc, GalA and Ara. The structure of LP-G2 was determined using IR and NMR spectroscopy. It was composed of →4)-β-d-galactose→4)-α-l-galactose-6- sulfate segments, with β-d-Glc and α-d-galactose unit substituted at the 6-position of α-l-galactose. Functional analysis showed that LP-G2 inhibited complement activation on both the classic and alternative pathways with CH50 value of 3.08 ± 0.25 mg/mL and AP50 value of 2.23 ± 0.20 mg/mL, respectively. Preliminary mechanism studies by using complement component depleted-sera indicated that LP-G2 selectively interacts with C1q, C2, C4 and C9. The results suggested that LP-G2 could be of potential benefits in treatment of the complement associated diseases.

Houttuynia cordata Thunb. is a traditional herb used for clearing heat and eliminating toxins, and has also been used for the treatment of severe acute respiratory syndrome (SARS). In vitro, the crude H. cordata polysaccharides (CHCP) exhibited potent anti-complementary activity through both the classical and alternative pathways by acting on components C3 and C4 of the complement system without interfering with the coagulation system. This study was to investigate the preventive effects of CHCP on acute lung injury (ALI) induced by hemorrhagic shock plus lipopolysaccharide (LPS) instillation (two-hit) and LPS-induced fever in rats. CHCP significantly attenuated pulmonary injury in the \"two-hit\" ALI model by reducing pulmonary edema and protein exudation in bronchoalveolar lavage fluid (BALF). In addition, it reduced the deposit of complement activation products in the lung and improved oxidant-antioxidant imbalance. Moreover, CHCP administration inhibited fever in rats, reduced the number of leukocytes and restored serum complement levels. The inhibition on the inappropriate activation of complement system by CHCP may play an important role in its beneficial effects on inflammatory diseases. The anti-complementary polysaccharides are likely to be among the key substances for the heat-clearing function of H. cordata.