Graphical abstract

Continuing our investigations on plants belonging to the Asclepiadaceae family, three new cardenolide glycosides, 3'-O-beta-D-glucopyranosylcalactin (1), 12-dehydroxyghalakinoside (2), and 6'-dehydroxyghalakinoside (3), along with the known ghalakinoside (4) and calactin (5), were isolated from the roots of Pergularia tomentosa. The structures of these compounds were elucidated by extensive spectroscopic methods including 1D- and 2D-NMR experiments as well as ESIMS analysis. The isolated cardenolides caused apoptotic cell death of Kaposi's sarcoma cells.