Castor oil

Castor oil is a vegetable oil obtained from the castor bean (technically castor seed as the castor plant, Ricinus communis, is not a member of the bean family). Castor oil (CAS number 8001-79-4) is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is 313 °C (595.4 °F) and its density is 961 kg·m^-3.^[1] It is a triglyceride in which approximately ninety percent of fatty acid chains are ricinoleic acid. Oleic and linoleic acids are the other significant components.^[2]

The structure of the major component of castor oil is shown below:

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Background

Ricinoleic acid, a monounsaturated, 18-carbon fatty acid, is unusual in that it has a hydroxyl functional group on the twelfth carbon. This functional group causes ricinoleic acid (and castor oil) to be unusually polar, and also allows chemical derivatization that is not practical with most other seed oils. It is the hydroxyl group which makes castor oil and ricinoleic acid valuable as chemical feedstocks. Compared to other seed oils which lack the hydroxyl group, castor oil demands a higher price. As an example, in July 2007 Indian castor oil sold for about US$0.90 per kilogram (US$0.41 per pound)^[3] while US soybean, sunflower and canola oil sold for about US$0.30 per kilogram (US$0.14 per pound)^[4]

Castor oil and its derivatives have applications in the manufacturing of soaps, lubricants, hydraulic and brake fluids, paints, dyes, coatings, inks, cold resistant plastics, waxes and polishes, nylon, pharmaceuticals and perfumes.

Sulfonated castor oil, also called Sulfonated (sulfated) castor oil, or Turkey Red Oil, is the only oil that completely disperses in water. It is made by adding sulfuric acid to pure castor oil^[5]. This allows easy use for making bath oil products. It was the first synthetic detergent after ordinary Soap. It is used in formulating lubricants, softeners, and dyeing assistants^[6].

The castor seed contains ricin, a toxic protein removed by cold pressing and filtering.^[7] However, harvesting castor beans is not without risk, ^[8] allergenic compounds found on the plant surface can cause permanent nerve damage, making the harvest of castor beans a human health risk. India, Brazil and China are the major crop producers and the workers suffer harmful side effects from working with these plants.^[9] These health issues, in addition to concerns about the toxic byproduct (ricin) from castor oil production, have encouraged the quest for alternative, domestic sources for hydroxy fatty acids.^[10][11] Alternatively, some researchers are trying to genetically modify the castor plant to prevent the synthesis of ricin.^[12]

Castor oil fatty acids

Uses

Castor oil in food

In the food industry, castor oil (food grade) is used in food additives [5], flavorings, candy (i.e., chocolate) ^[13], as a mold inhibitor, and in packaging. Polyoxyethylated castor oil (eg. Cremophor EL)^[14] is also used in the foodstuff industries.^[15]

Medicinal use of castor oil

The United States Food and Drug Administration (FDA) has categorized castor oil as "generally recognized as safe and effective" (GRASE) for over-the-counter use as a laxative.^[16] However, it is not a preferred treatment for constipation.^[17] Castor oil can also be used to induce childbirth, but doing so is sometimes recommended against because it can lead to complications for the childbirth process, including dehydration of the mother and other risks associated with any inducement of pregnancy, such as fetal distress from too strong contractions, increased risk of uterine rupture (especially in a scarred uterus), unintentional prematurity of the baby, and increased pain level for the mother.^[18]

Undecylenic acid, a castor oil derivative, is also FDA-approved for over-the-counter use on skin disorders or skin problems.^[19]

Ricinoleic acid is the main component of castor oil and it exerts anti-inflammatory effects.^[20]

One study has found that castor oil decreased pain more than ultrasound gel or Vaseline during extracorporeal shock wave application.^[21] Therapeutically, modern drugs are rarely given in a pure chemical state, so most active ingredients are combined with excipients or additives. Castor oil, or a castor oil derivative such as Cremophor EL (polyethoxylated castor oil, a nonionic surfactant), is added to many modern drugs, including:

• Miconazole, an anti-fungal agent;^[22][23]
• Paclitaxel, a mitotic inhibitor used in cancer chemotherapy;^[24]
• Sandimmune (cyclosporine injection, USP), an immunosuppressant drug widely used in connection with organ transplant to reduce the activity of the patient's immune system;^[25]
• Nelfinavir mesylate, an HIV protease inhibitor;^[26]
• Saperconazole, a triazole antifungal agent (contains Emulphor EL -719P, a castor oil derivative);^[27]
• Prograf, an immunosuppressive drug (contains HCO-60, polyoxyl 60 hydrogenated Castor oil);^{[citation needed]}
• Xenaderm ointment, a topical treatment for skin ulcers is a combination of Balsam Peru, Castor oil, and trypsin;^[28][29]
• Aci-Jel, a gel used to create or maintain the acidity of the vagina (comprises acetic acid/oxyquinoline/ricinoleic acid - vaginal)^[30]

Traditional or folk medicines

The use of cold pressed castor oil in folk medicine predates government regulations. Cold pressed castor oil is tasteless and odorless when pure. Uses include skin problems, burns, sunburns, skin disorders, skin cuts, abrasions, etc.

The oil is also used as a rub or pack for various ailments, including abdominal complaints, headaches, muscle pains, inflammatory conditions, skin eruptions, lesions, and sinusitis. A castor oil pack is made by soaking a piece of flannel in castor oil, then putting it on the area of complaint and placing a heat source, such as a hot water bottle, on top of it. This remedy was often suggested by the American Healing Psychic, Edgar Cayce, given in many healing readings in the early to mid-1900s.^[31]

Industrial castor oil

Castor oil has numerous applications in transportation, cosmetics and pharmaceutical, and manufacturing industries, for example: adhesives^[32], brake fluids ^[33], caulks, dyes^[32], electrical liquid dielectrics, humectants,^[32] hydraulic fluids, inks^[32], lacquers, leather treatments,^[32] lubricating greases, machining oils, paints^[32], pigments, polyurethane adhesives ^[34] , refrigeration lubricants, rubbers^[32], sealants, textiles^[32], washing powders, and waxes.

Vegetable oils, due to their good lubricity and biodegradability are attractive alternatives to petroleum-derived lubricants, but oxidative stability and low temperature performance limit their widespread use.^[35] Castor oil has better low temperature viscosity properties and high temperature lubrication than most vegetable oils, making it useful as a lubricant in jet, diesel, and race-car engines.^[36] However, castor oil tends to form gums in a short time, and its use is therefore restricted to engines that are regularly rebuilt, such as motorcycle race engines. Biodegradability results in decreased persistence in the environment (relative to petroleum-based lubricants^[37]) in case of an accidental release. The lubricants company Castrol took its name from castor oil.

Since it is has a relatively high dielectric constant (4.7), highly refined and dried castor oil is sometimes used as a dielectric fluid within high performance high voltage capacitors.

Castor oil is the raw material for the production of a number of chemicals, notably sebacic acid, undecylenic acid, nylon-11. A review listing numerous chemicals derived from castor oil is available.^[38]

Castor oil is the preferred lubricant for bicycle pumps, most likely because it doesn't dissolve natural-rubber seals.^[39]

Uses in early aviation and aeromodelling

Castor oil was the preferred lubricant for the early aviation powerplant design known as the rotary engine, such as the Gnome engines used in pre-World War I "pioneer aircraft", after that engine's widespread adoption for aviation in Europe in 1909, and was used almost universally by the rotary engines in World War I Allied aircraft.

The methanol-fuelled glow plug engines used for aeromodelling purposes, since their adoption in the model airplane hobby in 1948, have used castor oil as a dependable lubricant that is highly resistant to degradation when the engine has its fuel-air mixture "leaned out" for maximum engine speed. The aforementioned gummy residue problem can still be troublesome for aeromodelling powerplants lubricated with castor oil, however, usually resulting in eventual ball bearing replacement when the residue builds up too much within the engine's bearing races.

Castor oil: Use as a means of intimidation in Fascist Italy

In Fascist Italy under the regime of Benito Mussolini, castor oil was one of the tools of the blackshirts^{[40] [41] [42]} Political dissidents were force-fed large quantities of castor oil by Fascist paramilitary groups. This technique was said to have been originated by Gabriele D'Annunzio. Victims of this treatment would experience severe diarrhea and dehydration, often resulting in death ^[43]

Sometimes when the blackshirts wished to make sure that the victim would die rather than simply be badly disabled, they would mix gasoline with the castor oil.

It is said that Mussolini's power was backed by "the bludgeon and castor oil." In lesser quantities, castor oil was also used as an instrument of intimidation, for example to discourage civilians or soldiers who would call in sick either in the factory or in the military. Since its healing properties were widely exaggerated, abuse could be easily masked under pretense of a doctor's prescription. It took decades after Mussolini's death before the myth of castor oil as a panacea for a wide range of diseases and medical conditions was totally demystified, as it was also widely administered to pregnant women, elderly or mentally-ill patients in hospitals in the false belief that it had no negative side effects.

Linguistic connotations

Today the Italian terms manganello and olio di ricino, even used separately, still carry strong political connotations and if these words are still used to satirize patronizing politicians or the authors of unpopular legislation, they should be used with caution when engaging in a common conversation. Usare l'olio di ricino, ("to use castor oil") o usare il manganello ("use the bludgeon"), means to coerce or abuse and can be misunderstood in the absence of a proper context.

See also

• Castor plant
• Castor wax

References