Structure of a homofructosan from Saussurea costus and anti-complementary activity of its sulfated derivatives

A homogeneous water-soluble polysaccharide APS-W1, (2→1)-β-d-fructofuranosan, with an average molecular weight of 3.9kDa, was isolated and characterized from the roots of Saussurea costus. Five sulfated derivatives of APS-W1 with different degrees of sulfation were prepared and they showed strong inhibitory effect on the complement activation through the classical pathway (CP50: 2.2-18.9μg/mL; 8.3μg/mL for heparin) and alternative pathway (AP50: 11.4-115.8μg/mL; 89.2μg/mL for heparin). Mechanism studies by using complement-depleted sera indicated that sulfated derivatives with different positions of sulfation targeted to different complement proteins. Meanwhile the sulfated derivatives have limited anticoagulant effect based on re-calcification time and thrombin time. These results suggested that the sulfated derivatives prepared from APS-W1 could be promising potential complement inhibitors for the treatment of diseases caused by an over-activated complement system.