A new steroidal saponin from the seeds of Allium tuberosum

A steroidal saponin, named tuberoside A, together with six known compounds, were isolated from the seeds of Allium tuberosum Rottl. ex Spreng. On the basis of acid hydrolysis, comprehensive spectroscopic analyses and comparison with spectral data of known compounds, its structure was established as (24S, 25S)-5β-spirostan-2β,3β,24-triol 3-O-α-l-rhamnopyranoyl-(1→2)-O-[α-l-rhamnopyranosyl-(1→4)]-β-d-glucopyranoside. The six known compounds were thymidine, adenosine, 2-hydroxy purine, adenine, uracil, and thymine. 2-hydroxy purine, adenine, uracil and thymine are isolated from the seeds of A. tuberosum for the first time. This paper deals with the isolation and structural elucidation of the new saponin.