Bioactive Cycloartane-Type Triterpene Glycosides from Astragalus elongatus

Together with two known cycloartane-type glycosides, askendosides D (3-O-[α-arabinopyranosyl-( 1→2)-β-xylopyranosyl]-6-O-β-xylopyranosyl-cycloastragenol, 2) and G (3-O- [α-arabinopyranosyl-(1→2)-β-xylopyranosyl]-16-O-β-glucopyranosyl-3β,6α,16β,24(R),25- pentahydroxycycloartane, 3), also a new monodesmosidic cycloartane-type glycoside, elongatoside (1), was isolated from the roots of Astragalus elongatus and identified as 3-O- [α-arabinopyranosyl-(1→2)-β-xylopyranosyl]-cycloastragenol. All structures were unambiguously determined by means of spectroscopic and spectrometric methods (1D and 2D NMR, ESI-MS). The isolated compounds were tested for the inhibition of proliferation and ICAM-1 expression in vitro using the human microvascular endothelial cell line (HMEC-1). 1 showed weak activity in the ICAM-1 assay.

Spirostanol saponins and esculin from Rusci rhizoma reduce the thrombin-induced hyperpermeability of endothelial cells

Rusci rhizoma extracts are traditionally used against chronic venous disorders (CVD). To determine the effect of its secondary plant metabolites on the endothelium, phenolic compounds and saponins from Butcher's broom were isolated from a methanolic extract, and their activity on the thrombin-induced hyperpermeability of human microvascular endothelial cells (HMEC-1) was investigated in vitro. In addition to the six known spirostanol saponins deglucoruscin (5), 22-O-methyl-deglucoruscoside (6), deglucoruscoside (7), ruscin (8), ruscogenin-1-O-(α-l-rhamnopyranosyl-(1→2)-β-d-galactopyranoside (9) and 1-O-sulpho-ruscogenin (10), three new spirostanol derivatives were isolated and identified: 3'-O-acetyl-4'-O-sulphodeglucoruscin (1), 4'-O-(2-hydroxy-3-methylpentanoyl)-deglucoruscin (2) and 4'-O-acetyl-deglucoruscin (3). Furthermore, the coumarin esculin (4), which is also prominently present in other medicinal plants used in the treatment of CVD, was isolated for the first time from Rusci rhizoma. Five of the isolated steroid derivatives (2, 5, 8, 9 and 10) and esculin (4) were tested for their ability to reduce the thrombin-induced hyperpermeability of endothelial cells in vitro, and the results were compared to those of the aglycone neoruscogenin (11). The latter compound showed a slight but concentration-dependent reduction in hyperpermeability to 71.8% at 100μM. The highest activities were observed for the spirostanol saponins 5 and 8 and for esculin (4) at 10μM, and these compounds resulted in a reduction of the thrombin-induced hyperpermeability to 41.9%, 42.6% and 53.3%, respectively. For 2, 5 and 8, the highest concentration tested (100μM) resulted in a drastic increase of the thrombin effect. The effect of esculin observed at a concentration of 10μM was diminished at 100μM. These in vitro data provide insight into the pharmacological mechanism by which the genuine spirostanol saponins and esculin can contribute to the efficacy of Butcher's broom against chronic venous disorders.

Novel phenyl-1-benzoxepinols from butcher's broom (Rusci rhizoma)

Two novel compounds, (3S)-2,3-dihydro-3-(4-hydroxyphenyl)-1-benzoxepin-8-ol (ruscozepine A) and (3S)-2,3-dihydro-3-(4-hydroxyphenyl)-8-methoxy-1-benzoxepin-7-ol (ruscozepine B) were isolated from butcher's broom (Rusci rhizoma) together with a biosynthetically possible phenylethanoid precursor, hydroxytyrosol. The structures were elucidated by spectroscopic methods such as 1D- and 2D-NMR (COSY, HSQC, HMBC, ROESY), and HR-EI-MS experiments. The absolute configuration of the ruscozepines was determined by electronic circular dichroism.