Euphorbia

Succulent euphorbias are most diverse in southern and eastern Africa and Madagascar, but they also occur in tropical Asia and the Americas. The genus has roughly 2,000 members, making it one of the largest genera of flowering plants. Euphorbias range from tiny annual plants to large and long-lived trees. All of them share a poisonous, latex-like sap and unique floral structures. The flowers occur in a head called the cyathium, a feature present in every species of the genus but nowhere else in the plant kingdom.

The milky sap of spurges, called latex, evolved as a deterrent to herbivores. The latex is white and transparent when dry, except in E. abdelkuri, where it is yellow. Its skin-irritating and caustic effects are largely caused by varying amounts of diterpenes. Triterpenes such as betulin and corresponding esters are other major components of the latex. In contact with mucous membranes (eyes, nose, mouth), the latex can produce extremely painful inflammation. Congealed latex is insoluble in water, but can be removed with an emulsifier such as milk or soap.

Euphorbia resinifera, the resin spurge, is native to Morocco, where it occurs on the slopes of the Atlas Mountains. Its milky latex, in dried form, is called euphorbium. Euphorbium is an acrid dull-yellow or brown resin that dissolves in alcohol, ether and turpentine and is only slightly soluble in water. It consists of two or more resins and a substance euphorbone, C₂₀H₃₆O or C₁₅H₂₄O. Pieces of euphorbium are brittle, waxy and translucent, with a dull-yellow or yellowish-brown colour, and their taste is very acrid and burning. In former times euphorbium was valued in medicine for its drastic, purgative and emetic properties.

The main uses of spurges are horticultural. Poinsettia, Euphorbia pulcherrima, is the most widely grown pot plant in Europe, the United States, and other countries for the Christmas holiday season. Some species of Euphorbia have been used in folk medicine over the centuries, especially in the Euphorbia esula alliance. Latex of E. cooperi and E. ingens has been used locally in Africa to stun fish. Candelilla wax is obtained from E. antisyphilitica and used as a food additive, glazing agent, and component of lip balm.

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