| Ricinus communis Castor oil plant |
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|---|---|
| Castor bean in disturbed area | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Malpighiales |
| Family: | Euphorbiaceae |
| Subfamily: | Acalyphoideae |
| Tribe: | Acalypheae |
| Subtribe: | Ricininae |
| Genus: | Ricinus |
| Species: | R. communis |
| Binomial name | |
| Ricinus communis L. |
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The castor oil plant, Ricinus communis, is a species of flowering plant in the spurge family, Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Ricininae. The evolution of castor and its relation to other species are currently being studied.[1]
Its seed is the castor bean which, despite its name, is not a true bean. Castor is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, but is widespread throughout tropical regions (and widely grown elsewhere as an ornamental plant).[2]
Castor seed is the source of castor oil, which has a wide variety of uses. The seeds contain between 40% and 60% oil that is rich in triglycerides, mainly ricinolein. The seed contains ricin, a toxin, which is also present in lower concentrations throughout the plant.
Another plant species, Fatsia japonica, is similar in appearance and is known as the false castor oil plant.
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The castor oil plant can vary greatly in its growth habit and appearance. The variability has been increased by breeders who have selected a range of cultivars for leaf and flower colours, and for oil production. It is a fast-growing, suckering perennial shrub which can reach the size of a small tree (around 12 metres / 39 feet), but it is not cold hardy.
The glossy leaves are 15–45 centimetres (5.9–18 in) long, long-stalked, alternate and palmate with 5–12 deep lobes with coarsely toothed segments. In some varieties they start off dark reddish purple or bronze when young, gradually changing to a dark green, sometimes with a reddish tinge, as they mature. The leaves of some other varieties are green practically from the start, whereas in yet others a pigment masks the green colour of all the chlorophyll-bearing parts, leaves, stems and young fruit, so that they remain a dramatic purple-to-reddish-brown throughout the life of the plant. Plants with the dark leaves can be found growing next to those with green leaves, so there probably is only a single gene controlling the production of the pigment in some varieties at least.[3] The stems (and the spherical, spiny seed capsules) also vary in pigmentation. The fruit capsules of some varieties are more showy than the flowers.
The flowers are borne in terminal panicle-like inflorescences of green or, in some varieties, shades of red monoecious flowers without petals. The male flowers are yellowish-green with prominent creamy stamens and are carried in ovoid spikes up to 15 centimetres (5.9 in) long; the female flowers, born at the tips of the spikes, have prominent red stigmas.[4]
The fruit is a spiny, greenish (to reddish-purple) capsule containing large, oval, shiny, bean-like, highly poisonous seeds with variable brownish mottling. Castor seeds have a warty appendage called the caruncle, which is a type of elaiosome. The caruncle promotes the dispersal of the seed by ants (myrmecochory).
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 resemble certain ticks. The common name "castor oil" probably comes from its use as a replacement for castoreum, a perfume base made from the dried perineal glands of the beaver (castor in Latin). It has another common name, palm of Christ, or Palma Christi, that derives from castor oil's reputed ability to heal wounds and cure ailments.
Castor oil has many uses in medicine and other applications.
Alcoholic extract of the leaf was hepatoprotective in rats.[5][6][7] Methanolic extracts of the leaves of Ricinus communis were used in antimicrobial testing against eight pathogenic bacteria in rats and showed antimicrobial properties. The extract was not toxic.[8] The pericarp of castor bean showed central nervous system effects in mice at low doses. At lower doses, the extract improved memory consolidation. At high doses mice quickly died.[9] A water extract of the root bark showed analgesic activity in rats.[10] Antihistamine and anti-inflammatory properties were found in ethanolic extract of Ricinus communis root bark.[11]
Extract of Ricinus communis, exhibited acaricidal and insecticidal activities against the adult of Haemaphysalis bispinosa Neumann (Acarina: Ixodidae) and hematophagous fly Hippobosca maculata Leach (Diptera: Hippoboscidae).[12]
The Bodo tribals of Bodoland, Assam (India), use the leaves of this plant to feed and rear the larvae of muga and endi silkworms.
Castor oil is a good motor lubricant and has been used in internal combustion engines, including those of World War I airplanes, some racing cars and some model airplanes. It has advantages over petroleum based oils, especially at high and low temperatures. It does not mix with petroleum products. It has been largely replaced by synthetic oils that are more stable and less toxic.
Although castor is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, today it is widespread throughout tropical regions.[2] In areas with a suitable climate, castor establishes itself easily as an apparently "native" plant and can often be found on wasteland.
It is also used extensively as a decorative plant in parks and other public areas, particularly as a "dot plant" in traditional bedding schemes. If sown early, under glass, and kept at a temperature of around 20 °C (68 °F) until planted out, the castor oil plant can reach a height of 2–3 metres (6.6–9.8 ft) in a year. In areas prone to frost it is usually shorter, and grown as if it were an annual.[2] However, it can grow well outdoors in cooler climates, at least in southern England, and the leaves do not appear to suffer frost damage in sheltered spots, where it remains evergreen. It was used in Edwardian times in the parks of Toronto, Ontario, Canada.[13]
Selections have been made by breeders for use as ornamental plants (heights refer to plants grown as annuals) and for commercial production of castor oil[4]
Ornamental varieties:
(all the above grow to around 1.5 metres (4.9 ft) tall as annuals)[2]
Varieties for oil production:
Ricinus communis is the host plant of the Common Castor Butterfly (Ariadne merione), the Eri silkmoth (Samia cynthia ricini), and the Castor Semi-Looper Moth (Achaea janata). It is also used as a food plant by the larvae of some other species of Lepidoptera, including Hypercompe hambletoni and the Nutmeg (Discestra trifolii).
The toxicity of raw castor beans due to the presence of ricin is well-known. Although the lethal dose in adults is considered to be four to eight seeds, reports of actual poisoning are relatively rare.[14] According to the 2007 edition of the Guinness Book of World Records, this plant is the most poisonous in the world. Despite this suicides involving ingestion of castor beans are unheard of in countries like India where castor grows abundantly on the roadsides. There is reason to believe therefore that further research on the apparent high toxicity of small quantities of castor beans is necessary. However, it is well known that the poison can be extracted from Castor by concentrating it with a fairly complicated process similar to that used for extracting cyanide from almonds.
If ingested, symptoms may be delayed by up to 36 hours but commonly begin within 2-4 hours. These include a burning sensation in mouth and throat, abdominal pain, purging and bloody diarrhea. Within several days there is severe dehydration, a drop in blood pressure and a decrease in urine. Unless treated, death can be expected to occur within 3–5 days, however in most cases a full recovery can be made.[15][16] In most cases, on ingestion of the broken seeds, drinking a teaspoon of cold-pressed castor oil will prevent any poisoning.
Poisoning occurs when animals, including humans, ingest broken seeds or break the seed by chewing: intact seeds may pass through the digestive tract without releasing the toxin[15]. Toxicity varies among animal species: four seeds will kill a rabbit, five a sheep, six an ox or horse, seven a pig, and eleven a dog. Ducks have shown incredible resistance to the seeds: it takes an average of 80 to kill them.[17] The toxin provides the castor oil plant with some degree of natural protection from insect pests, such as aphids. In fact, ricin has been investigated for its potential use as an insecticide. The castor oil plant is also the source for undecylenic acid, a natural fungicide.
Commercially available cold-pressed castor oil is not toxic to humans in normal doses, either internal or externally. [18]
Three terpenoids and a tocopherol-related compound have been found in the aerial parts of Ricinus communis. Compounds named (3E,7Z,11E)-19-hydroxycasba-3,7,11-trien-5-one, 6α-hydroxy-10β-methoxy-7α,8α-epoxy-5-oxocasbane-20,10-olide, 15α-hydroxylup-20(29)-en-3-one, and (2R,4aR,8aR)-3,4,4a,8a-tetrahydro-4a-hydroxy-2,6,7,8a-tetramethyl-2-(4,8, 12-trimethyltridecyl)-2H-chromene-5,8-dione were isolated from the methanol extracts of Ricinus communis by chromatographic methods.[19]
Global castor seed production is around one million tons per year. Leading producing areas are India (with over three-quarters of the global yield), China and Brazil, and it is widely grown as a crop in Ethiopia. There are several active breeding programmes.
| Top ten castor oil seed producers — 11 June 2008 | ||||
|---|---|---|---|---|
| Country | Production (Tonnes) | Footnote | ||
| India | 830 000 | * | ||
| People's Republic of China | 210 000 | * | ||
| Brazil | 91 510 | |||
| Ethiopia | 15 000 | F | ||
| Paraguay | 12 000 | F | ||
| Thailand | 11 052 | |||
| Vietnam | 5 000 | * | ||
| South Africa | 4 900 | F | ||
| Philippines | 4 500 | F | ||
| Angola | 3 500 | F | ||
| World | ' 1 209 756 ' | A | ||
| No symbol = official figure, P = official figure, F = FAO estimate, * = Unofficial/Semi-official/mirror data, C = Calculated figure A = Aggregate (may include official, semi-official or estimates); |
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In Brazil, castor oil (locally known as mamona oil) is now being used to produce biodiesel. In rural areas, the abundant seeds are used by children for slingshot balls, as they have the right weight, size, and hardness.
The attractive castor seeds are used in jewelry, mainly necklaces and bracelets.
Castor oil was traditionally used on the skin to prevent dryness. This is now used as a base for many cosmetics.
Castor oil in a processed form, called Polyglycerol polyricinoleate--or PGPR, is currently being used in chocolate bar manufacture as a less expensive substitute to cocoa butter.
Castor oil is often used in the USA to repel moles and voles for lawn care.
Castor seeds have been found in Egyptian tombs dating back to 4000 BC; the slow burning oil was used mostly to fuel lamps. Herodotus and other Greek travelers noted the use of castor seed oil for lighting, body ointments, and improving hair growth and texture. Cleopatra is reputed to have used it to brighten the whites of her eyes. The Ebers Papyrus is an ancient Egyptian medical treatise believed to date from 1552 BC. Translated in 1872, it describes castor oil as a laxative.
The use of castor bean oil ("eranda") in India has been documented since 2000 BC in lamps and in local medicine as a laxative, purgative, and cathartic in Unani, Ayurvedic and other ethnomedical systems. Traditional Ayurvedic medicine considers castor oil the king of medicinals for curing arthritic diseases. It is regularly given to children orally, for de-worming.
Castor seed and its oil have also been used in China for centuries, mainly prescribed in local medicine for internal use or use in dressings.
It was used in rituals of sacrifice to please the gods in early civilizations.
Castor oil is known to have been used as an instrument of coercion by the paramilitary Blackshirts under the regime of Italian dictator Benito Mussolini. Dissidents and regime opponents were forced to ingest the oil in large amounts, triggering severe diarrhoea and dehydration, which could ultimately cause death. This punishment method was originally thought of by Gabriele D'Annunzio, the Italian poet and Fascist supporter, during the First World War. (See also: Castor oil: Use as a means of intimidation in Fascist Italy)
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