Characterisation of an anticomplement polysaccharide BP-S1 from seeds of Brucea javanica

Bioactivity-guided purification obtained polysaccharide BP-S1 from seeds of Brucea javanica. The results showed that BP-S1 was a homogenous polysaccharide with molecular weight of 45.7 kDa, mainly composed of arabinose and glucose in the ratio of 1.0:1.0 and the backbone of BP-S1 was deduced to be →3,4)-α-Glup-(1→ with branches of →2)-α-Arap-(1→and α-Arap-(1→, and the possible repetitive units were speculated according to result of methylation and 2D-NMR. Moreover, BP-S1 is a periodic rope-like structure. Functional analysis revealed that BP-S1 inhibited complement activation on the classic and alternative pathways with values of CH₅₀ 0.073 ± 0.012 mg/mL and AP₅₀ 0.097 ± 0.004 mg/mL, respectively. In mechanism study, using complement component depleted-sera methods indicated that BP-S1 selectively interacted with C3 and C4 components.