Cardenolide glycosides from root of Streptocaulon juventas

Six cardenolides were isolated from the anti-tumor active fraction of the 75% ethanol extract of Streptocaulon juventas (Asclepiadaceae), mainly found in southwest of China. These were named 1α, 14β-dihydroxy-5β-card-20 (22)-enolide 3-O-[O-β-D-glucopyranosyl-(1→2)-β-D-digitalopyranoside] (1), acovenosigenin A 3-O-[O-β-D-glucopyranosyl-(1→4)-β-D-digitalopyranoside] (2), 16-O-acetyl-hydroxyperiplogenin 3-O-β-D-digitoxopyranoside (3), digitoxigenin 3-O-[O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl-(1→4)-2-O-acetyl-β-D-digitalopyranoside] (4), 16-O-acetyl-hydroxyacovenosigenin (5), 1β, 3β, 14β-trihydroxy-5β-card-16, 20 (22)-dienolide (6), together with 18 known ones, most of which had never been reported in the species beforehand. Their structures were elucidated on the basis of spectroscopic studies and comparison with reference. Eighteen compounds were evaluated for their cytotoxicity against human lung A549 adenocarcinoma cell lines.