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Abstract:
In several European countries, especially in Sweden, the seeds of the species
Astragalus boeticus L. were widely used as coee substitutes during the 19th century. Nonetheless,
data regarding the phytochemistry and the pharmacological properties of this species are
currently extremely limited. Conversely, other species belonging to the Astragalus genus have
already been extensively investigated, as they were used for millennia for treating various
diseases, including cancer. The current work was addressed to characterize cycloartane
glycosides from A. boeticus, and to evaluate their cytotoxicity towards human colorectal
cancer (CRC) cell lines. The isolation of the metabolites was performed by using dierent
chromatographic techniques, while their chemical structures were elucidated by nuclear
magnetic resonance (NMR) (1D and 2D techniques) and electrospray-ionization quadrupole
time-of-flight (ESI-QTOF) mass spectrometry. The cytotoxic assessment was performed in vitro by
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays in Caco-2, HT-29 and
HCT-116 CRC cells. As a result, the targeted phytochemical study of A. boeticus enabled the isolation
of three new cycloartane glycosides, 6-O-acetyl-3-O-(4-O-malonyl)--d-xylopyranosylcycloastragenol
(1), 3-O-(4-O-malonyl)--d-xylopyranosylcycloastragenol (2), 6-O-acetyl-25-O--d-glucopyranosyl-
3-O--d-xylopyranosylcycloastragenol (3) along with two known compounds,
6-O-acetyl-3-O--d-xylopyranosylcycloastragenol (4) and 3-O--d-xylopyranosylcycloastragenol
(5). Importantly, this work demonstrated that the acetylated cycloartane glycosides 1 and 4 might
preferentially inhibit cell growth in the CRC cell model resistant to epidermal growth factor receptor (EGFR) inhibitors.
