Structural characterization of a homogalacturonan from Capparis spinosa L. fruits and anti-complement activity of its sulfated derivative

A water-soluble polysaccharide CSPS-2B-2 with a molecular mass of 8.8 kDa, was obtained from the fruits of Capparis spinosa L. Chemical and NMR spectral analysis verified CSPS-2B-2 was a linear poly-(1-4)-alpha-D-galactopyranosyluronic acid in which 12.9 +/- 0.4 % of carboxyl groups existed as methyl ester and 2.6 +/- 0.1 % of D-GalpA residues were acetylated. A sulfated derivative Sul-2B-2 with a sulfation degree of 0.88 +/- 0.02 was prepared via the substitution of C-2 and/or C-3 of GalpA residues in CSPS-2B-2. Bioassay on the complement and coagulation system demonstrated that Sul-2B-2 (CH50: 3.5 +/- 0.2 mu g/mL) had a stronger inhibitory effect on the activation of complement system through the classic pathway than that of heparin (CH50: 8.9 +/- 0.3 mu g/mL). Interestingly, Sul-2B-2 at low dose even middle dose (for example 52 mu g/mL) had no effect on coagulation system, which was totally different from heparin. Thus, our observation indicated that Sul-2B-2 was more efficient than heparin in inhibiting the activation of the complement system through classical pathway and exhibiting a relatively less anti-coagulant activity. These results suggested that the sulfated derivative Sul-2B-2 prepared from the homogalacturonan in the fruits of Capparis spinosa L, might be a promising drug candidate in case of necessary therapeutic complement inhibition.