The milky sap contains a complex mix of chemicals, some of which are steroidal heart poisons known as & x22;cardiacàaglycones& x22;. These belong to the same chemical family as similar chemicals found in foxgloves & x28;Digitalis purpurea& x29;. The steroidal component includes an hydroxyl group in the C3ò position, a second attached to the C14 carbon, a C/D-cisring junction and an ñ,ò-unsaturated-ó-lactone in the C17 position. In the plants, the steroidal component is commonly attached via a glycosidic link to a 2-desoxy or a 2,6-didesoxy sugar molecule. The features described are those required for toxicity but in addition there can be other substitutions into the steroid nucleus. These can be a C19-aldehyde in place of the more usual methyl group in this position as well as additional hydroxyl functions and sometimes epoxide structures
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