Pancreatic Lipase-Inhibiting Triterpenoid Saponins from Fruits of Acanthopanax senticosus

Sixteen triterpenoid saponins were isolated from the fruits of Acanthopanax senticosus, including a new compound, acanthopanaxoside E (1), which was established as 3-O-β-D-glucuronopyranosyl echinocystic acid 28-O-β-D-glucopyranoside on the basis of various spectroscopic analyses and chemical degradation. By using a pancreatic lipase-inhibiting assay system, the crude saponin fraction showed inhibitory activity on pancreatic lipase, which is a key enzyme in lipid digestion. Among the isolated compounds, silphioside F (2), copteroside B (3), hederagenin 3-O-β-D-glucuronopyranoside 6'-O-methyl ester (4) and gypsogenin 3-O-β-D-glucuronopyranoside (5) showed inhibitory activity toward pancreatic lipase with IC_<50> values of 0.22, 0.25, 0.26 and 0.29 mM, respectively, and the free carboxylic acid groups in position 28 within their chemical structures were required for enhancement of pancreatic lipase inhibition.