Karataviosides G-K, five new bisdesmosidic steroidal glycosides from the bulbs of Allium karataviense.

We have analyzed the steroidal glycosides in Allium karataviense bulbs, and isolated five new bisdesmosidic steroidal glycosides: karataviosides G-K (1-5). The structures were elucidated by extensive spectroscopic analysis, including 2D NMR and enzymatic and hydrolytic cleavage. Karatavioside G (1) is an entirely novel furostanol glycoside, which has an O-ß-d-glucopyranosyl-(1→6)-ß-d-glucopyranosyl-(1→6)-ß-d-glucopyranosyl unit at C-26 of the aglycone. Although a variety of cholestanol glycosides have been isolated, mainly from Liliaceae and Agavaceae, karataviosides J and K (4 and 5) are also notable because they are the most polar cholestanol bisdesmosides discovered, in which a lycotetraose is attached to C-3 of the aglycone, and a glucose or O-glucosyl-(1→3)-glucose is attached at C-16. The isolated glycosides were also evaluated for their cytotoxic activities against cultured tumor cell lines.