The cardiac glycoside named from the Somali word for arrow poison and found in Strophanthus gratus is ouabain.
The name passed into English through French ouabaïo from Somali waabaayo, meaning “arrow poison.” In eastern Africa, extracts from plants such as Strophanthus gratus and Acokanthera schimperi were traditionally applied to hunting and warfare arrows. Ouabain occurs in several parts of the plant, including its seeds, leaves, stems, and roots.
Pharmacologically, ouabain blocks the sodium–potassium ATPase, the membrane pump that maintains sodium and potassium gradients. This changes intracellular calcium handling and can strongly affect cardiac contraction, which explains both its historical medical interest and its danger as a poison. It was investigated as a cardiac drug, although modern treatment has largely replaced it.
A common mix-up is strophanthidin: it is a related aglycone associated with strophanthin compounds, not the canonical name asked for here. Convallatoxin is another cardiac glycoside, derived from lily of the valley, while theobromine is a methylxanthine found notably in cocoa.