Medicinal plants play a crucial role in traditional medicine and in the maintenance of human health worldwide. Sesquiterpene lactones represent an interesting group of plant-derived compounds that are currently being tested as lead drugs in cancer clinical trials.
Achillea falcata is a medicinal plant indigenous to the Middle Eastern region and belongs to the Asteraceae family, which is known to be rich in sesquiterpene lactones. We subjected
Achillea falcata extracts
to
bioassay-guided fractionation against the growth of HCT-116 colorectal cancer cells
and identified four secotanapartholides, namely 3-β-methoxy- isosecotanapartholide (
1), isosecotanapartholide (
2), tanaphallin (
3), and 8-hydroxy-3-methoxyisosecotanapartholide (
4). Three highly oxygenated guaianolides were isolated for the first time from
Achillea falcata, namely rupin A (
5), chrysartemin B (
6), and 1β, 2β-epoxy- 3β,4α,10α-trihydroxyguaian- 6α,12-olide (
7). These sesquiterpene lactones showed no or minor cytotoxicity while exhibiting promising anticancer effects against HCT-116 cells. Further structure-activity relationship studies related the bioactivity of the tested compounds to their skeleton, their lipophilicity, and to the type of functional groups neighboring the main alkylating center of the molecule.
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