Lupane-type triterpenoidal saponins from Pulsatilla chinensis and their anticomplement activities through the classical pathway

Four (1-4) previously unknown lupane-type triterpenoidal saponins were isolated from the roots of Pulsatilla chinensis, along with six triterpene saponins (5-10). The structures of saponins 1-4 were determined as 23-hydroxy-3β-[(O-β-D-glucopyranosyl-(1 → 4)-α-L-arabinopyranosyl)]lup-20(29)-en-28-oic-acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (1), 23-hydroxy-3β-[(O-α-L-rhamnopyranosyl-(1 → 2)-[β-D-glucopyranosyl-(1 → 4)]-α-L-arabinopyranosyl)]lup-20(29)-en-28-oic-acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (2), 3β-[(O-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl)]lup-20(29)-en-28-oic-acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (3), and 3β-[(O-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl)]lup-20(29)-en-28-oic-acid 28-O-α-L-rhamnopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (4), on the basis of hydrolysis and spectral evidence, including 1D- and 2D-NMR and HR-ESI-MS analyses. These pure isolates (1-10) were tested for their anticomplement activity, using an in vitro assay of the Complement System of the classical pathway.