Spectroscopic Characterization and Cytotoxicity Assessment towards Human Colon Cancer Cell Lines of Acylated Cycloartane Glycosides from <i>Astragalus boeticus</i> L.

In several European countries, especially in Sweden, the seeds of the species <i>Astragalus boeticus</i> L. were widely used as coffee 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 <i>Astragalus</i> 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 <i>A. boeticus</i>, and to evaluate their cytotoxicity towards human colorectal cancer (CRC) cell lines. The isolation of the metabolites was performed by using different 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 <i>A. boeticus</i> enabled the isolation of three new cycloartane glycosides, 6-<i>O</i>-acetyl-3-<i>O</i>-(4-<i>O</i>-malonyl)-&#946;-<span style="font-variant: small-caps;">d</span>-xylopyranosylcycloastragenol (<b>1</b>), 3-<i>O</i>-(4-O-malonyl)-&#946;-<span style="font-variant: small-caps;">d</span>-xylopyranosylcycloastragenol (<b>2</b>), 6-<i>O</i>-acetyl-25-<i>O</i>-&#946;-<span style="font-variant: small-caps;">d</span>-glucopyranosyl-3-<i>O</i>-&#946;-<span style="font-variant: small-caps;">d</span>-xylopyranosylcycloastragenol (<b>3</b>) along with two known compounds, 6-<i>O</i>-acetyl-3-<i>O</i>-&#946;-<span style="font-variant: small-caps;">d</span>-xylopyranosylcycloastragenol (<b>4</b>) and 3-<i>O</i>-&#946;-<span style="font-variant: small-caps;">d</span>-xylopyranosylcycloastragenol (<b>5</b>). Importantly, this work demonstrated that the acetylated cycloartane glycosides <b>1</b> and <b>4</b> might preferentially inhibit cell growth in the CRC cell model resistant to epidermal growth factor receptor (EGFR) inhibitors.

Abstract licence: CC BY

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