Castor oil is a vegetable oil extracted from the seeds of the castor bean plant (Ricinus communis). It is widely used for its various therapeutic, cosmetic, and industrial applications due to its unique properties.

Chemical Composition and Structure:

Castor oil primarily consists of:

• Ricinoleic Acid: The main fatty acid in castor oil, comprising approximately 90% of its fatty acids. It has unique properties that contribute to the oil's medicinal and cosmetic benefits.
• Other Fatty Acids: Includes oleic acid, linoleic acid, and palmitic acid, which contribute to the oil's overall fatty acid profile.
• Glycerides: The fatty acids are esterified with glycerol, forming triglycerides.

Physical Properties:

• Appearance: Clear to pale yellow liquid
• Odor: Mild, characteristic of castor beans
• Texture: Viscous and thick, with a slightly sticky feel

Production Process:

The production of castor oil involves:

1. Harvesting: Castor beans are harvested from the castor plant.
2. Extraction: The seeds are subjected to mechanical pressing or solvent extraction to obtain the oil.
3. Refinement: The crude oil is refined to remove impurities and improve clarity, stability, and safety.

Applications:

• Medical: Castor oil is used as a laxative and for its potential anti-inflammatory and antimicrobial properties. It is also used in some therapeutic formulations for skin conditions and joint pain.
• Cosmetics: In skincare, castor oil is valued for its moisturizing, emollient, and anti-inflammatory properties. It is found in creams, lotions, lip balms, and hair care products to enhance hydration and smoothness.
• Others: Castor oil is used in industrial applications, including the production of lubricants, coatings, and polymers due to its unique chemical properties.

Environmental and Safety Considerations:

Castor oil is generally considered safe for use and biodegradable. However, it is important to ensure that the oil is sourced sustainably and is free from contaminants. Castor oil can cause allergic reactions or skin irritation in some individuals, so patch testing is recommended when used in cosmetics.

References__________________________________________________________________________

Sandford EC, Muntz A, Craig JP. Therapeutic potential of castor oil in managing blepharitis, meibomian gland dysfunction and dry eye. Clin Exp Optom. 2021 Apr;104(3):315-322. doi: 10.1111/cxo.13148. Epub 2021 Mar 10. PMID: 33037703.

Abstract. The multifactorial pathogenesis and interrelationship of blepharitis, meibomian gland dysfunction and dry eye disease poses challenges to any therapeutic approach. Current treatments are mostly palliative, with success limited by perceived inefficacy and poor patient compliance. Castor oil, a natural derivative of the Ricinus communis plant, is widely used as an emollient in cosmetics and personal care products, drug delivery systems and wound dressings. Castor oil is deemed safe and tolerable, with strong anti-microbial, anti-inflammatory, anti-nociceptive, analgesic, antioxidant, wound healing and vaso-constrictive properties. Its main constituent, ricinoleic acid, has a bipolar molecular structure that promotes the formation of esters, amides and polymers. These can supplement deficient physiological tear film lipids, enabling enhanced lipid spreading characteristics and reducing aqueous tear evaporation. Studies reveal that castor oil applied topically to the ocular surface has a prolonged residence time, facilitating increased tear film lipid layer thickness, stability, improved ocular surface staining and symptoms. This review summarises the properties, current uses of, and therapeutic potential of castor oil in managing ocular surface disease. The biochemical, medicinal actions of castor oil are explored from the perspective of ocular surface pathology, and include microbial and demodectic over-colonisation, inflammatory and oxidative processes, as well as clinical signs and symptoms of dryness and discomfort.

McKeon TA, Lin JT, Stafford AE. Biosynthesis of ricinoleate in castor oil. Adv Exp Med Biol. 1999;464:37-47. doi: 10.1007/978-1-4615-4729-7_4.

Abstract. Castor oil is 90% ricinoleate (12-hydroxyoleate) and has numerous industrial uses. Components of castor bean (Ricinus communis L.) pose serious problems to processors. Other researchers have cloned the gene for the oleoyl hydroxylase, but transgenic plants produce only about 20% hydroxy fatty acid. To improve such transgenic substitutes for castor, we are using HPLC analysis of castor bean microsomal suspensions to follow the hydroxylase reaction and the movement of 14C-ricinoleate through phospholipid into triacylglycerol. Most labeled ricinoleate is rapidly removed from the phospholipid fraction as free fatty acid and incorporated into triacylglycerol, with triricinolein predominating. Elucidation of the basis for high incorporation of ricinoleate and exclusion of oleate from triacylglycerols will identify genes that can be used to engineer high ricinoleate production in transgenic plants.

Final report on the safety assessment of Ricinus Communis (Castor) Seed Oil, Hydrogenated Castor Oil, Glyceryl Ricinoleate, Glyceryl Ricinoleate SE, Ricinoleic Acid, Potassium Ricinoleate, Sodium Ricinoleate, Zinc Ricinoleate, Cetyl Ricinoleate, Ethyl Ricinoleate, Glycol Ricinoleate, Isopropyl Ricinoleate, Methyl Ricinoleate, and Octyldodecyl Ricinoleate. Int J Toxicol. 2007;26 Suppl 3:31-77. doi: 10.1080/10915810701663150. PMID: 18080873.

Abstract. The oil derived from the seed of the Ricinus communis plant and its primary constituent, Ricinoleic Acid, along with certain of its salts and esters function primarily as skin-conditioning agents, emulsion stabilizers, and surfactants in cosmetics, although other functions are described. Ricinus Communis (Castor) Seed Oil is the naming convention for castor oil used in cosmetics. It is produced by cold pressing the seeds and subsequent clarification of the oil by heat. Castor oil does not contain ricin because ricin does not partition into the oil. Castor oil and Glyceryl Ricinoleate absorb ultraviolet (UV) light, with a maximum absorbance at 270 nm. Castor oil and Hydrogenated Castor Oil reportedly were used in 769 and 202 cosmetic products, respectively, in 2002; fewer uses were reported for the other ingredients in this group. The highest reported use concentration (81%) for castor oil is associated with lipstick. Castor oil is classified by Food and Drug Administration (FDA) as generally recognized as safe and effective for use as a stimulant laxative. The Joint Food and Agriculture Organization (FAO)/World Health Organization (WHO) Expert Committee on Food Additives established an acceptable daily castor oil intake (for man) of 0 to 0.7 mg/kg body weight. Castor oil is hydrolyzed in the small intestine by pancreatic enzymes, leading to the release of glycerol and Ricinoleic Acid, although 3,6-epoxyoctanedioic acid, 3,6-epoxydecanedioic acid, and 3,6-epoxydodecanedioic acid also appear to be metabolites. Castor oil and Ricinoleic Acid can enhance the transdermal penetration of other chemicals. Although chemically similar to prostaglandin E(1), Ricinoleic Acid did not have the same physiological properties. These ingredients are not acute toxicants, and a National Toxicology Program (NTP) subchronic oral toxicity study using castor oil at concentrations up to 10% in the diet of rats was not toxic. Other subchronic studies of castor oil produced similar findings. Undiluted castor oil produced minimal ocular toxicity in one study, but none in another. Undiluted castor oil was severely irritating to rabbit skin in one study, only slightly irritating in another, mildly irritating to guinea pig and rat skin, but not irritating to miniature swine skin. Ricinoleic Acid was nonirritating in mice and in one rabbit study, but produced well-defined erythema at abraded and intact skin sites in another rabbit study. Zinc Ricinoleate was not a sensitizer in guinea pigs. Neither castor oil nor Sodium Ricinoleate was genotoxic in bacterial or mammalian test systems. Ricinoleic Acid produced no neoplasms or hyperplasia in one mouse study and was not a tumor promoter in another mouse study, but did produce epidermal hyperplasia. Castor oil extract had a strong suppressive effect on S(180) body tumors and ARS ascites cancer in male Kunming mice. No dose-related reproductive toxicity was found in mice fed up to 10% castor oil for 13 weeks. Female rats injected intramuscularly with castor oil on the first day after estrus had suppressed ovarian folliculogenesis and anti-implantation and abortive effects. Castor oil used as a vehicle control in rats receiving subcutaneous injections had no effect on spermatogenesis. A methanol extract of Ricinus communis var. minor seeds (ether-soluble fraction) produced anti-implantation, anticonceptive, and estrogenic activity in rats and mice. Clinically, castor oil has been used to stimulate labor. Castor oil is not a significant skin irritant, sensitizer, or photosensitizer in human clinical tests, but patients with occupational dermatoses may have a positive reaction to castor oil or Ricinoleic Acid. The instillation of a castor oil solution into the eyes of nine patients resulted in mild and transient discomfort and minor epithelial changes. In another study involving 100 patients, the instillation of castor oil produced corneal epithelial cell death and continuity breaks in the epithelium. Because castor oil contains Ricinoleic Acid as the primary fatty acid group, the Cosmetic Ingredient Review (CIR) Expert Panel considered the safety test data on the oil broadly applicable to this entire group of cosmetic ingredients. The available data demonstrate few toxic effects. Although animal studies indicate no significant irritant or sensitization potential, positive reactions to Ricinoleic Acid in selected populations with identified dermatoses did suggest that sensitization reactions may be higher in that population. Overall, however, the clinical experience suggests that sensitization reactions are seen infrequently. In the absence of inhalation toxicity data on these ingredients, the Panel determined that these ingredients can be used safely in aerosolized cosmetic products because the particle sizes produced are not respirable. Overall, the CIR Expert Panel concluded that these cosmetic ingredients are safe in the practices of use and concentrations as described in this safety assessment.