Structure and cytotoxicity of steroidal glycosides from Allium schoenoprasum

A phytochemical analysis of the whole plant of Allium schoenoprasum, has led to the isolation of seven new spirostane-type glycosides (1-7) while 1-6 were obtained as three pairs of inseparable (R)/(S)-isomers derivatives 1/2, 3/4, 5/6, and four known steroidal saponins. Their structures were elucidated mainly by 2D NMR spectroscopic analysis and mass spectrometry as (20S,25R)-spirost-5-en-3β,12β,21-triol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (1) and its (25S)-isomer (2), (20S,25R)-spirost-5-en-3β,11α,21-triol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (3) and its (25S)-isomer (4), laxogenin 3-O-α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-β-D-glucopyranoside (5) and its (25S)-isomer (6), and (25R)-5α-spirostan-3β,11α-diol 3-O-β-D-glucopyranosyl-(1→3)-[β-D-glucopyranosyl-(1→4)]-β-D-galactopyranoside (7). Four of the isolated compounds were tested for cytotoxic activity against the HCT 116 and HT-29 human colon cancer cell lines.