Bidesmosidic Oleanane Saponins from Xerospermum noronhianum

Three new oleanane‐type triterpenoid saponins, 3‐ O ‐( α ‐ L ‐rhamnopyranosyl(1→2)‐ β ‐ D ‐fucopyranosyl)‐28‐ O ‐{[ α ‐ L ‐rhamnopyranosyl(1→2)] [ β ‐ D ‐fucopyranosyl(1→6)]‐ β ‐ D ‐glucopyranosyl} oleanolic acid ( 1 ), 3‐ O ‐[ α ‐ L ‐rhamnopyranosyl(1→3)‐ β ‐ D ‐fucopyranosyl]‐28‐ O ‐[ α ‐ L ‐rhamnopyranosyl(1→4)‐ β ‐ D ‐glucopyranosyl] oleanolic acid ( 2 ), and 3‐ O ‐{ α ‐ L ‐rhamnopyranosyl(1→2)‐[3′,4′‐diacetoxy‐ β ‐ D ‐fucopyranosyl]}‐28‐ O ‐[ α ‐ L ‐rhamnopyranosyl(1→2)‐ β ‐ D ‐glucopyranosyl] oleanolic acid ( 3 ) have been isolated from the stems of Xerospermum noronhianum. The structures of the saponins were determined as a series of bidesmosidic oleanane saponins based on spectral evidence. The anticholinesterase activity of the saponins 1 – 3 was also evaluated.