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

Abstract

Cirsium setosum (C. setosum) has a potential antihyperglycemic effect, but it is unclear what bioactive components play a key role. According to the α-glucosidase inhibition activity, three new taraxastane-type triterpenoids of 3β-hydroxy-30-hydroperoxy-20-taraxastene (1), 3β-hydroxy-22α-methoxy-20-taraxastene (2), and 30-nor-3β,22α-dihydroxy-20-taraxastene (3), as well as five known taraxastane triterpenoids of 3β,22-dihydroxy-20-taraxastene (4), 20-taraxastene-3,22-dione (5), 3β-acetoxy-20-taraxasten-22-one (6), 3β-hydroxy-20-taraxasten-22-one (7), and 30-nor-3β-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 α-glucosidase inhibitory activity—with IC50 values of 18.34 ± 1.27, 26.98 ± 0.89, 17.49 ± 1.42, and 22.67 ± 0.25 μM, respectively—than acarbose did (positive control, IC50 42.52 ± 0.32 μM).

Bioactive Usual and Unusual Triterpenoids Derived from Natural Sources Used in Traditional Medicine

“…In contrast, as a positive control, acarbose had a higher IC 50 of 42.52±0.32 μM ( Figure 7). These findings support using C. setosum as a dietary supplement in hypoglycemic products [110] …”

“…These findings support using C. setosum as a dietary supplement in hypoglycemic products. [110] Furthermore, C. setosum stem extract soluble in petroleum ether yielded two molecules, 22-oxo-20taraxasten-3, 30-diol, and 22-hydroxy-20-taraxasten-30, 30-triol, which demonstrated moderate cytotoxic against the human ovarian (A2780) and colon (HCT-8) cancer cell lines with IC 50 values of 2.6 and 3.8 μM, respectively. [111] Euphorbia denticulata Lam (Euphorbia), a perennial herb, is generally used in gout and back pain as a laxative and locally used for warts and sores.…”

“…C. setosum is a significant component of Xiao‐Ji, a traditional Chinese medicine, and its preparations have been labeled as supplements for liver and cardiovascular illness in the United States. C. setosum is utilized as a health drink in China for its hypoglycemic, hypolipidemic, and anti‐inflammatory properties [110] and is a potential source of taraxastane‐type triterpenoids. The ethanolic extract of C. setosum , fractionated with petroleum ether, afforded 3 β ‐hydroxy‐30‐hydroperoxy‐20‐taraxastene ( 125 ), 3 β ‐hydroxy‐22 α ‐methoxy‐20‐taraxastene ( 126 ), 3 β ‐,22‐dihydroxy‐20‐taraxastene ( 127 ), 3 β ‐hydroxy‐20‐taraxasten‐22‐one ( 128 ), 30‐nor‐3 β ‐hydroxy‐20‐taraxastene, 3 β ‐acetoxy‐20‐taraxasten‐22‐one, 30‐nor‐3 β ‐,22 α ‐dihydroxy‐20‐taraxastene, and 20‐taraxastene‐3,22‐dione.…”

“…The genus Eugenia (Myrtaceae) consists of approximately 600 species in the tropics and is a good source of a variety of triterpenoids. One of the most studied oleanane-type triterpenoids is arjunolic acid (110), and it performs several biological and pharmaceutical activities, including antibacterial, anti-inflammatory, antioxidant, antidiabetic, antihyperlipidemic, cardio- protective, antitumor, anticancer, and hepatoprotective, and 110 is used as a cardio-protective phytotonic in traditional Ayurvedic medicine for centuries. [89] The perennial herb Aceriphyllum rossii Engler (Saxifragaceae) grows in valleys on wet rocks and is an endemic species in the Republic of Korea's mid-northern region.…”