Rubber bush (Calotropis procera)
is a species of flowering plant in the family Apocynaceae that is native to North Africa, 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, stabragh, king's crown,
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.
Rubber bush is a spreading shrub or a small tree to 4 m, oozing copious milky sap when cut or broken. Leaves are opposite, grey-green, broadly elliptic but varying between ovate and obovate, large up to 15 cm long and 10 cm broad, with a pointed tip, two rounded basal lobes and no leaf stalk. Flowers are waxy white, petals 5, purple-tipped inside and with a central purplish crown, carried in stalked clusters at the ends of the branches. Fruit is grey-green, inflated, 8-12 cm long, containing numerous seeds with tufts of long silky hairs at one end.
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.
The bark and leaves are used for the treatment of leprosy and asthma, respectively.
Compounds derived from the plant have been found to have emetic-cathartic and digitalic properties. The principal active compounds are asclepin and mudarin. Other compounds have been found to have bactericidal and vermicidal properties. The extremely poisonous roots are used in the treatment of snakebites. The milky sap is used as a rubefacient and is also strongly purgative and caustic.
The latex is used for treating ringworm, guinea worm blisters, scorpion stings, venereal sores and ophthalmic disorders, it is also used as a laxative. Its use in India in the treatment of skin diseases has caused severe bullous dermatitis leading sometimes to hypertrophic scars. The local effect of the latex on the conjunctiva is congestion, epiphora and local anesthesia.