Calotropis procera is a species of flowering plant in the family Apocynaceae that is native to North Africa, Pakistan,tropical Africa, Western Asia, South Asia, and Indochina. The green fruits contain a toxic milky sap that is extremely bitter and turns into a gluey coating which is resistant to soap.
Common names for the plant include Apple of Sodom, Sodom apple, king's crown, rubber bush, and rubber tree. The name Apple of Sodom and Dead Sea Apple comes from the fact that the ancient authors Josephus and Tacitus described it as growing in the area of biblical Sodom.
The milky sap contains a complex mix of chemicals, some of which are steroidal heart poisons known as "cardiac aglycones". These belong to the same chemical family as similar ones found in foxgloves (Digitalis purpurea).The plant contains steroidal components that are the cause of its toxicity. In the case of the Calotropis glycosides, their names are calotropin, calotoxin, calactin, uscharidin and voruscharin. The plant is known to occur throughout the tropical belt and is also common in the West Indies (e.g. Jamaica), where the locals know it as "pillow cotton". When the ripe "apples" burst, the fibrous contents are ejected along with the seeds. The former are collected by the Jamaicans and used for filling pillows. The giant milkweed is used for fibre and medicine in Southern Africa, but it rapidly invades subsistence agricultural fields reducing yields. The plant is poisonous if eaten by livestock. It thrives in the hot northern regions of Limpopo Province. This plant is also found along road verges and in drainage lines.