Secondary Metabolites from Astragalus lycius and Their Cytotoxic Activities

Eight known secondary metabolites were isolated from the methanolic extract of the whole plant of Astragalus lycius Boiss. They were identified as 5,5′-dihydroxy-3′-methoxy-isoflavone-7- O-β-D-glucoside (1), genistin (2), sissotrin (3), 5,4′-dimethoxy-isoflavone-7- O-β-D-glucopyranoside (4), (7 S,8 R)-5-methoxydehydrodiconiferyl alcohol-4- O-β-D-glucopyranoside (5), 4- O-lariciresinol-glucoside (6), 2-phenylethyl-β-D-glucopyranoside (7) and β-sitosterol-3- O-β-D-glucopyranoside (8) by spectroscopic methods including 1H- and 13C-NMR and HR-MS experiments, and by comparison with literature values. Compounds 1–7 are reported for the first time from Astragalus taxa. All of the compounds were tested for their cytotoxic activities against a number of cancer cell lines. Among them, only 6 exhibited significant activity against human colon carcinoma (HT-29) at 2.69 μM concentration.

Synthesis, antimicrobial and cytotoxic activities, and structure-activity relationships of gypsogenin derivatives against human cancer cells

A series of gypsogenin (1) derivatives (1a-i) was synthesized in good yields, and the derivatives' structures were established using UV, IR, (1)H NMR, (13)C NMR, and LCMS spectroscopic data. Among the tested compounds, 1a, 1b, 1d, 1e, and gypsogenin (1) showed antimicrobial activities against Bacillus subtilis and Bacillus thrungiensis, with inhibition zones of 10-14 mm. In addition, compounds 1b, 1d, and 1e showed antimicrobial activities against Bacillus cereus, with inhibition zones of 9-14 mm. Using six human cancer cell lines in vitro, the cytotoxic activities of all tested compounds were determined by calculating the IC50 values. Doxorubicin and paclitaxel were used as controls. Among the tested compounds, 1a, 1c, and 1d had inhibitory effects with IC50 values of 3.9 μM (HL-60 cells), 5.15 μM (MCF-7 cells), and 5.978 μM (HL-60), respectively. To determine the type of cell death, Hoechst 33258 (HO) and propidium iodide (PI) double staining was used. Especially, gypsogenin (1) and compound 1a triggered the apoptotic mechanism at a concentration of 20 μM. Thus, gypsogenin (1) and compounds 1a, 1c, and 1d possess varying degrees of biological activities and can be considered as potential antitumor agents.

Triterpene Saponins from Knautia integrifolia var. bidens

Two new triterpene saponins (1 and 2), named bidenosides A and B, were isolated from the roots of Knautia integrifolia var. bidens. The structures were identified as 3-O-α-L-rhamnopyranosyl-28- O-[β -D-allopyranosyl-(1→6)-β -D-glucopyranosyl]-pomolic acid, and 3-O-α-L-rhamnopyranosyl- 28-O-[β -D-allopyranosyl-(1→6)-β -D-glucopyranosyl]-oleanolic acid on the basis of spectroscopic evidence.

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.

α-Glucosidase Inhibitory Constituents of Linaria kurdica subsp. eriocalyx

Three known iridoid glycosides, antirrhide (1), antirrhinoside (2), and 5- O-β-allosylantirrhinoside (3), and two known flavone glycosides, linariin (4″′- O-acetylpectolinarin) (4) and linarin (acacetin-7- O-β-D-rutinoside) (5) were isolated from Linaria kurdica Boiss & Hohen. subsp. eriocalyx The structures of the isolated compounds were established from spectroscopic evidence. Compounds 1-3 showed high inhibitory potential against α-glucosidase.