Castor oil is made from the annual oilseed crop called castor (Ricinus communis) a vegetable oil common in the Eastern part of the world. The oil is widely known for its laxative properties. However, other health benefits such as uterine contraction, lipid metabolism, and antimicrobial activity have been reported.
Castor oil is colourless to very pale yellow liquid with a distinct taste and odour.
The FDA has only approved the use of castor oil as a stimulative laxative for the temporary relief of occasional constipation
Castor oil is extracted from the seed using n-hexane. India, China, and Brazil lead in global castor oil production. The oil is used in agricultural, pharmaceutical, and industrial sectors for producing ointments, nylon, varnishes, airplane engine lubricants, hydraulic fluids, dyes, detergents, plastics, synthetic leather, cosmetics, and perfumes.
Composition
Castor oil is made of mostly fatty acids and neutral lipids (triglycerides). There are other bioactive compounds such as phytosterols, tocopherols, carotenoids, phenolics, phospholipids, and tocotrienol.
Triglycerides
Most of the triacylglycerides found in the oil has three molecules of ricinoleic acid linked to a glycerol moiety. Examples of the triacylcerides include the primary triglyceride, triricinolein, and others like trilinolein, triolein, tripalmitin, triestearin, and trilionlenin.
Factors such as the planting region, cultivar, harvesting period, oil extraction process, and storage affect the composition of the triacylcerides in castor oil.
Fatty Acids
Castor oil has ricinoleic, oleic, linoleic, linolenic acid, stearic, palmitic acid, among others. The most concentrated fatty acid is the monounsaturated fatty acid, ricinoleic acid, with 75 to 90% of the total oil’s composition.
Phytosterols
Phytosterols are one of the minor bioactive compounds in castor oil. 4-desmethylsterols, β-sitosterol, Campesterol, stigmasterol, and Δ-5 avenasterol are found in the oil.
Phospholipids
Phospholipids are lipids that form lipid bilayers in the cell membrane. Phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine are found in small quantity in the oil.
Tocopherols and tocotrienols
Four naturally tocopherols (α-, β-, γ-, and δ-tocopherol) have been identified in oilseeds including castor. α- and β-tocotrienols are the tocotrienols found in the oilseed.
Phenolic compounds
Phenolic acids present include ferulic, syringic, p-coumaric, o-coumaric, chlorogenic, gallic, gentistic, protocatechuic, and cinnamic.
Caroteinoids
Carotenoids like β-carotene are powerful antioxidant and scavenge free radicals.
Health Benefits of Castor Oil
The presence of linolenic acid and oleic acid in castor oil is beneficial to human health. They can help to prevent diseases such as diabetes, high blood pressure, renal disease, cancer, and high cholesterol levels.
Carotenoids, tocopherols, and tocotrienols are two powerful antioxidants and anti-inflammatory compounds found in the oil seed. They inhibit oxidation of body lipids, organelle membranes, and reduce the risk of diseases like Alzheimer’s, cancer, and heart disease. Phytosterols helps to reduce the low-density lipoprotein cholesterol levels.
Apart from the approved use of the oil seed as a laxative, the oil has been used traditionally to treat arthritis, headache, menstrual cramps, wound, and for labor induction. Other potential health benefits include managing blepharitis, dry eye disease, and meibomian gland dysfunction.
The preparation of castor oil may reduce milk flow or as a galactagogue, though there is little scientific backing to this claim.
As a Laxative
Castor oil has been approved by the FDA as a stimulative laxative for the temporary relief of occasional constipation. It is of benefit in carrying out bowel prep during diagnostic test such as colonoscopy. However, other laxatives such as sennosides, polyethylene glycol (PEG), and bisacodyl are more effective with less side effects.
Castor oil, bisacodyl and sennosides all belong to the stimulant laxative category.
Mechanism of Action:
Ricinoleic acid is responsible for the laxative effect of castor oil. Lipase breaks down the oil into ricinoleic acid in the intestine, activating EP3 and EP4 prostanoid receptors in smooth muscle cells.
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This activation will lead to a transient calcium surge, causing propulsion in the intestine.
Dosage:
Castor oil is available as a 100% oral solution. The daily dosage for an adult is 15 to 60 mL.
Castor oil benefits for skin
Linoleic, palmitic, stearic acids have important properties that are utilized in the cosmetic industry. The esters of stearic acid: glycol distearate, glycol stearate, and ethylene glycol are used to make cosmetic products or to improve the pearly effect of shampoos.
Castor oil benefits for hair
Castor oil is used to improve hair growth, reduce dandruff, treat dry scalp, and also moisturize the hair. This is due to the rich ricinoleic acid content. It is usually mixed with other oils (like almond or olive) and applied to the scalp or hair.
Induction of Labour
Prostaglandins, oxytocin, and misoprostol have been used for cervical ripening and labor induction. But castor oil use for this purpose is a practice in some settings.
Castor oil has been used for induction of labour though there has been few scientific literature to back this practice. The theory is the since EP3 and EP4 prostanoid receptors are also present in the uterus, it could help as a laxative to aid cervical ripening and labor induction.
Adverse Effects
When compared to other stimulant laxative like sennosides, castor oil is more likely to cause abdominal cramping, vomiting, bloating, and dizziness. Also, people who use castor oil-containing lip balms or glosses may have symptoms like pruritus and erythema on the lips.
Contraindication
Castor oil affects smooth muscle and therefore, it is not recommended in pregnancy, as it may cause premature contractions. Also, stimulant laxatives are avoided in conditions such as gastrointestinal obstruction, appendicitis, perforation, and inflammatory bowel disease.
The oil should not be administered to infants due to the potential adverse effects.
Toxicity
Castor oil is completely safe for human consumption with minimal side effects. However, Ricinus seeds has a toxic chemical called ricin. If the seed is ingested directly, it may cause symptoms of ricin toxicity like gastrointestinal bleeding, shock, pulmonary edema, and inflammation.
These effect which have both acute and late-phase manifestations. The acute phase involves gastrointestinal symptoms while the late phase is experienced 2 to 5 days after exposure and is characterized by cytotoxic effects on the kidney, liver, and adrenal gland.
It is important to note that during the heating process of the castor bean, the ricin is deactivated, allowing the oil to be used safely
References
- https://www.researchgate.net/publication/345766202_Castor_oil_Ricinus_communis_a_review_on_the_chemical_composition_and_physicochemical_properties
- https://www.ncbi.nlm.nih.gov/books/NBK551626/
- https://www.arcjournals.org/pdfs/ijcclm/v10-i1/2.pdf
- https://www.chem.uwec.edu/chem491_w01/%20Pharmacognosy%20491/castor%20bean%20chemistry.pdf