Anti-complementary activity of a degraded sulfated heterogalactan from red alga Pyropia haitanensis

Abstract 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.