The plant has been cultivated for over 6000 years and was a source of oil for lamps and cosmetics in ancient Egypt. The toxicity of the plant has been well publicised as a result of a political assassination in London that was carried out using an umbrella tipped with the plant's main toxin, ricin. Greek physicians of the first century AD regarded the oil as suitable only for external application, a view which persisted until the 18th century, when it was listed in many pharmacopoeias as a purgative. The generic name is from the Latin ricinus, meaning 'tick', because the mottled seeds of the plant are similar in shape to these insects. The Egyptian Ebers papyrus of c. 1500 BC lists the plant.
The castor oil plant is probably native to eastern Mrica, but it is cultivated in hot climates around the world, especially India and other parts of southern Asia. It is also widely naturalised.
A tall, glaucus, branched shrub, reaching up to 4 m in height (Plate 51). The stem is erect and hollow, greyish-green when young and becoming brownish-red when older. The leaves are petioled, green and occasionally frosted blue or red, and arranged in a spiral. The blade is peltate, usually divided into palmate, ovate-oblong or Ian ceo late lobes up to 60 cm in diameter. The ribs are palmate and the margins irregularly serrate. The inflorescences are terminal panicles, 15-50 cm long, with the female flowers in the upper section of the inflorescence. The perianth is divided into five lobes and the style has three red, doubly split stigma branches. The male flowers bear numerous, heavily branched stamens with up to 1000 separate bursting anthers. The fruit capsule is soft and prickly or smooth and grooved, 1-2.5 cm in diameter. The capsule bursts open when ripe, showing the large, brightly speckled seeds. Castor oil is fatty oil obtained from the seeds.
Oil, leaves, seeds and root.
Castor oil is used internally in folk medicine for acute constipation, intestinal inflammation, for removal of worms, rheumatism and as a form of birth control. The extracts of the seeds are also used for this purpose. The oil is used externally for inflammatory skin disorders, furuncles, carbuncles, abscesses, inflammation of the middle ear and headaches. In Chinese medicine oil is used to treat sore throat, facial paralysis, dry stool, furuncles, ulcers and festering inflammation of the skin. The leaves are used as an emmenagogue, antiinflammatory and febrifuge and the root has been used to treat liver diseases and various forms of inflammation. Castor oil is used as a lubricant in hard candy production, as a component of protective coatings in tablets and as a flav.our component.
It is used as feed after detoxification.
Brassicasterol, campesterol, ?-Sitosterol, ?amyrin, lupeol and derivatives are present in the aerial parts.
Epicatechin, corilagin, ellagic, gallic, chlorogenic and neo-chlorogenic acids, hyperoside, kaempferol, quercetin, isoquercetin and rutin, 6,7-dihydroxy-8?methoxy coumarin and 6,8-dihydroxy-3,4-dimethoxy coumarin3-6 are all present in the aerial parts.
Ricinine is present in the seed.
Ricin-A, B, C, D and E, and IX-, ?- andy?ricin8-1? have been found in the seed,
Ricinoleic acid is the main component of the oil, together with linoleic, palmitic, oleic and stearic acids.
Lipolytic activity: Ricin showed lipolytic activity on neutral lipids both in emulsions and in a membrane-like model. The activity was found to be proportional to ricin and substrate concentrations and to be pH and galactose dependent. These data support the idea that a lipolytic step may be involved in the process of cell poisoning by ricin.
Antibacterial activity: Various types of extracts exhibit antibacterial activity, including an ethanolic extract of an in vitro callus culture of Ricinus communis which showed activity against six bacterial strains,I' The methanol extract of the root was active against Staphylococcus aureus and produced weak activity against Shigella boydii. II The ethanol extract of the dried leaf was active against Bacillus subtilis as well as. Staphylococcus aureus and an acetone extract against Serratia marcescens, Shigella flexneri, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and others. The water extract was active on E. coli, F. aeruginosa, S. 1jJphi, Sh. flexneri, Sarcina lutea and Staph. aureus.
Anthelmintic adivity: Potent anthelmintic activity was observed from a tissue culture of the plant against Mesocestoides corti and Taenis crassiceps.
Immunomodulating activity: Peptides from the seeds have been used in the preparation of immunomodulating drugs controlling the production of tumour necrosis factor (TNF).
Central neroous system (CNS) stimulant: An extract of the pericarp of the castor bean showed typical CNS stimulant effects when administered to mice. The animals became exophthalmic, presented tremors and clonic seizures, and died a few minutes after receiving high doses of the extract. At lower doses, the extract improved memory consolidation and showed some neuroleptic?like properties, including a decrease in exploratory behaviour and catalepsy. Similar properties were also observed using ricinine, a neutral alkaloid isolated from the extract. The therapeutic index of ricinine is of the order of 200 and it may therefore be a promising cognition-enhancing drug.
Laxative effects: Castor oil has been used since ancient times as a laxative, the active principle being ricinoleic acid. This hydroxylated, long-chain fatty acid has multiple effects on the intestinal mucosa, resulting in fluid secretion. Mucosal effects were considered to be due to enteritis or interference with cellular metabolism but more recent studies have revealed that castor oil increases mucosal permeability, associated with release of eicosanoids, platelet-activating factor, other autacoids and nitric oxide. In addition, ricinoleic acid disrupts normal intestinal motility. The combination of these effects on the mucosa and smooth muscle of the gut is thought to account for its laxative action. Castor oil decreases fluid absorption and increases secretion in the small intestine and colon and decreases activity of the circular smooth muscle, which is believed to produce an increase in intestinal transit. The mechanism by which it produces the effect on the gut may involve inhibition ofNa+ and K+-ATPase, activation of adenylate cyclase, stimulation of prostaglandins and nitric oxide biosynthesis. Castor oil changes the intestinal permeability and causes histological abnormalities, but these alterations are not essential for the laxative effect. Platelet-activating factor (PAF) is most likely one of the mediators of castor oil?induced damage, while nitric oxide has a protective role possibly by reducing PAF biosynthesis. Other properties may be due to the presence of lectins which interfere with bacterial adhesion.
Antiinflammatory activity: The petroleum ether extract exhibited significant antiinflammatory activity against induced rat paw arthritis and was safe up to a dose of 1 glkg PO. A water extract of the root bark showed analgesic activity when administered to rats, using the tail-flick response to radiant heat.
Hepatoprotective activity: The alcoholic extract of the leaf showed activity against galactosamine- and paracetamol-induced hepatotoxicity in rats. N-demethylricinine, isolated from the butanol fraction, was found to be the active compound. It restored the altered levels of several enzymatic and non?enzymatic parameters in the serum and liver and in hepatocytes isolated from paracetamol-treated rats, the compound reversed the biochemical changes produced by galactosamine. It was also found to possess significant choleretic and anticholestatic effects. An ethanol:water (1: 1) extract of the root was active on hepatocytes against carbon tetrachloride?induced hepatotoxicity and PGE-induced paw oedema.
Abortifacient and contraceptive activity: The oil showed abortifacient activity when taken orally by pregnant women. Extracts of the seed have been tested in women and found to produce long-term contraception.
Anticonvulsant activity: The ethanol extract of the fresh root, administered to mice at variable dosage levels, was active against phenmetrazole-ind uced convulsions.
Diuretic effects: Ethanol extracts of the seed and an aqueous extract of the aerial parts produced diuresis when administered intragastrically to rats.
Antifilarial and nematocidal activity: Methanol extract of the dried leaf was effective against Onchocerca volvulus. Castor leaves alone, or in combination with different levels ofN, P and K-enhanced plant growth fertilisers, reduced the nematode population.
Antiamoebic activity: Ethanol:water (1: 1) extracts of the root and stem in broth culture were active against Entamoeba histolytica.
Antischistosomal activity: The seed oil, when administered intragastrically to mice at a dose of 0.3 mllday for 7 days, showed activity against Schistosoma mansonii.
Antioxidant effects: Ricinus communis extract produced an inhibition of aryl hydrocarbon hydroxylase (AHH) activity and HZ02 production by lindane-induced mouse hepatic micro somes, indicating the antioxidant activity of the plant. The methanol extract of the seed also demonstrated strong antioxidant activity.
The seeds are highly toxic and ornamental use increases the likelihood of poisoning, since they may have been drilled, rupturing the seed coat and exposing the contents, If swallowed without chewing, poisoning is less likely because the impermeable seed coat remains intact. The oil is used more commonly and as the protein ricin is denatured during processing, therapeutic dosages of castor oil are reasonably safe, The oil should be used only occasionally and is contraindicated in intestinal obstruction, acute inflammatory intestinal diseases, appendicitis, abdominal pain of unknown origin, during pregnancy and lactation, The drug should not be administered to children under 12 years of age.
