Bioassay-Guided Isolation of Triterpenoids as -Glucosidase Inhibitors from Cirsium setosum

Cirsium setosum (C. setosum) has a potential antihyperglycemic effect, but it is unclear what bioactive components play a key role. According to the -glucosidase inhibition activity, three new taraxastane-type triterpenoids of 3-hydroxy-30-hydroperoxy-20-taraxastene (1), 3-hydroxy-22-methoxy-20-taraxastene (2), and 30-nor-3,22-dihydroxy-20-taraxastene (3), as well as five known taraxastane triterpenoids of 3,22-dihydroxy-20-taraxastene (4), 20-taraxastene-3,22-dione (5), 3-acetoxy-20-taraxasten-22-one (6), 3-hydroxy-20-taraxasten-22-one (7), and 30-nor-3-hydroxy-20-taraxastene (8) were obtained from the petroleum ether-soluble portion of the ethanol extract from C. setosum. All chemical structures of the compounds were elucidated by spectroscopic data analysis and compared with literature data. Compounds 4-8 were identified for the first time from this plant, and compounds 1, 2, 4, and 7 exhibited more potent -glucosidase inhibitory activitywith IC50 values of 18.34 +/- 1.27, 26.98 +/- 0.89, 17.49 +/- 1.42, and 22.67 +/- 0.25 M, respectivelythan acarbose did (positive control, IC50 42.52 +/- 0.32 M).