A Steroidal Saponin from the Seeds of Allium tuberosum

In order to investigate its bioactive compounds, we studied the chemical constituents of the seeds of Allium tuberosum systematically. Our detailed investigation of its seeds has led to the discovery of a new saponin. The new steroidal saponin, named tuberoside B, was 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 the new compound, its structure was established as (24S,25S)-5β-spirostan-2α,3β,5,24-tetraol 3-O-α-L-rhamnopyranoyl-(1 → 2)-O-[α-L-rhamnopyranosyl-(1 → 4)]-β-D-glucopyranoside. The new compound was identified by direct comparison with authentic samples (co-TLC, IR, MS, NMR) and with reported spectral and physical data. This paper deals with the isolation and structural elucidation of the new saponin.