RESUMO
Five unusual seco-nortriterpenoids, 3ß-hydroxy-20,21-seco-30-nortaraxastan-20,21-dioic acid (1), 3ß-hydroxy-20,21-seco-30-nortaraxastan-20-oic-21-oate (2), 3ß-hydroxy-20-oxo-21,22-seco-30-nortaraxastan-22-oic acid (3), 3ß-hydroxy-19-oxo-20,21-seco-29,30-nortaraxastan-21-oic acid (4) and 3ß-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.