An Androstane Bioside and 3'-Thiazolidinone Derivatives of Doubly-linked Cardenolide Glycosides from the Roots of Asclepias tuberosa

Steroidal compounds in the roots of Asclepias tuberosa were investigated and 17α-hydroxyandrosta-4, 6, 15-trien-3-one 17-O-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranoside, termed ascandroside, was isolated from the CHCl3-soluble fraction. Among five doubly-linked cardenolide glycosides, two were identified as 3'-spiro-linked thiazolidinone (4) and S-oxythiazolidinone derivatives (5) of Δ5-calotropin. The stereochemistry at the C-3' in these two cardenolides is discussed. 3'-O-β-D-Glucopyranosyl-Δ5-calotropin (3) was also isolated along with Δ5-calotropin and its 3'-acetate. Nine glycosides of uzarigenin, coroglaucigenin and corotoxigenin were identified.