Calosides A-F, Cardenolides from and Their Cytotoxic Activity.

Phytochemical analysis of the roots of led to the isolation of six new cardenolide glycosides, calosides A-F (-), and five known cardenolides (-). The structures of - were elucidated based on NMR and ECD spectroscopic data interpretation. Caloside D () is the first naturally occurring example of a cardenolide containing a C-8/C-19 oxygen bridge. In turn, calosides E () and F () represent the first naturally occurring 3--cannogenol diglycosides having potent cytotoxicity against the PANC-1 cell line (IC, 0.081 and 0.070 μM, respectively) and HeLa (IC, both 0.17 μM) cells, under normoglycemic conditions.