Unusual secondary metabolites from Astragalus halicacabus LAM

From the whole plant of Astragalus halicacabus (Sect. Halicacabus), a new cycloartane-type glycoside, (20R,24S)-3-O-[α-L-arabinopyranosyl-(1→2)-β-D-xylopyranosyl]-20,24-epoxy-16-O-β-D-glucopyranosyl-3β,6α,16β,25-tetrahydroxycycloartane, and a new glycoside, 3-O-[β-D-apiofuranosyl-(1→2)-β-D-glucopyranosyl]maltol were isolated together with seven known cycloartane-type glycosides, i.e., cyclocanthoside D, askendosides D, F, and G, cyclosieversioside G, cyclostipuloside A, elongatoside, and a known maltol glucoside, 3-O-β-D-glucopyranosylmaltol. The structures were elucidated by means of high-resolution mass spectrometry, and extensive 1D- and 2D-NMR spectroscopic analysis. This is the first phytochemical work on A. halicacabus, and a maltol glycoside was encountered for the first time in the Leguminosae family.

Astragalus halicacabus; Cycloartanes; Glycosides; Maltol glycosides.