Seco-nortriterpenoids from Cirsium setosum and their anti-inflammatory activity

Five unusual seco-nortriterpenoids, 3β-hydroxy-20,21-seco-30-nortaraxastan-20,21-dioic acid (1), 3β-hydroxy-20,21-seco-30-nortaraxastan-20-oic-21-oate (2), 3β-hydroxy-20-oxo-21,22-seco-30-nortaraxastan-22-oic acid (3), 3β-hydroxy-19-oxo-20,21-seco-29,30-nortaraxastan-21-oic acid (4) and 3β-hydroxy-19-oxo-20,21-seco-19-norlupan-21-oic acid (5) were isolated and elucidated from the anti-inflammatory activity fraction of the ethanol extract of Cirsium setosum. The structures of these compounds were established through spectroscopic methods. Preliminary biological assays showed that compounds 1–5 had significant inhibitory effect on NO production on lipopolysaccharide-stimulated RAW 264.7 cells, and compound 1 showed the strongest anti-inflammatory activity. This type of ring-opening compound is the first seco-triterpenoid structure discovered from the genus of Cirsium.