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Castor

Description and Cultivation

The castor bean (latin Ricinus communis) is not a true bean, but a member of the Euphorbiaceae or spurge family. It is the source of castor oil, which has a wide variety of uses, and ricin, a poison. The name Ricinus is a Latin word for tick; the seed is so named because it has markings and a bump at the end which resembles certain ticks.

Although castor is probably indigenous to Eastern Africa, today castor is distributed worldwide. Castor establishes itself easily as a "native" plant and can often be found on wasteland, near rail roads and has recently also been used extensively as decorative plant in parks etc.

Although monotypic, the castor plant can vary greatly in its growth habit and appearance. Some castor plants are perennials which can take the size of small trees; other plants are dwarf types and are grown as annuals. There also exists an enormous variation in leaf shape and colouring which has lead to a selection by breeders for use as ornamental plants.

Global castor seed production is around 1 million tons per year. Leading producing areas are India, China, Brazil and the former USSR. There are several active breeding programmes for castor.

Castor oil

Castor seed contains between 40% and 60% oil which is rich in tryglycerides, mainly ricinolein.

The unique composition of castor oil opens up a vast range of applications, and also permits it to be chemically transformed into a host of other useful forms. This is due to its unusual molecular structure. The oil is mainly composed of ricinoleic acid, a glyceride that does not otherwise occur in nature and is difficult to synthesize; it is characterized by a hydroxyl group and an isolated double bond. It is highly soluble in alcohol and has a viscosity twenty times greater than that of any other fat or oil of vegetable or animal origin.

The main uses of castor oil include the industrial production of coatings based on dehydrated alkyd resins. But it is also employed to make pharmaceuticals and cosmetics, in the textile and leather industries, and for manufacturing plastics and fibres. Polyols for polyurethane systems (especially two-component polyurethane coatings and structural foams) are also derived from it, as well as soaps, printing inks, plasticizers, wetting agents, and lubricants.

About 1% of the global castor oil production goes into medical or health store products. It is used to ease constipation and as an emetic to induce vomiting. Consumption of large amounts of castor oil (below lethal doses, such as one bottle) can induce labor in near-term pregnant women.

The poison ricin is made from the by-products in the manufacture of castor oil.