Castor Oil
CAS NO: 8001-79-4
REQUIRED HLB: 14
SAP: 176-186
NaOH SAP - 0.129, KOH SAP: 0.181
SHELF LIFE: 12-18 months approx
INCI: Ricinus communis (Castor) Oil
Appearance: Pale yellow, thick liquid
Unsaponifiable Matter: 1%
Iodine Value: 82-90
Castor oil comes from the cold expression of the beans of Ricinus communis, also called the castor plant. The castor plant is naturally found across the continents of Africa, India, and South America. The benefits of this oil have been reaped for thousands of years. Its earliest recorded use dates back to the Egyptian civilization when it was used for treating eye irritation and to induce labour (1).
Its unique composition and high levels of ricinoleic acid make it a useful lubricant in different industries but it also finds extensive usage in cosmetics and skincare products.
Chemistry of Castor Oil
Castor oil is extracted from the beans of the castor plant. Castor bean contains approximately 45% oil. The seeds are cold-pressed to obtain the viscous, pale yellow oil which has a characteristic bland flavor and aroma. The seeds contain a lethal toxin called “ricin” which is inactivated when the oil is heated. The oil is non toxic but ingesting it can illicit a strong laxative effect.
Castor oil is dominated by ricinoleic acid making up to 85-92% of the total oil composition. Other components include palmitic, linoleic, stearic, and oleic acids. Unlike other natural oils that can vary depending on their geographical region or extraction methods, castor oil is surprisingly uniform and consistent in it’s physical characteristics.
Ricinoleic acid, a rare omega 9 monosaturated fatty acid, make up a very high proportion of this oil. Among fatty acids, ricinoleic acid is unusual in that it has a hydroxyl functional group on the 12th carbon. This functional group results in ricinoleic acid (and castor oil) having greater polarity than most fats. It contributes to its unique viscosity and solubility in alcohols. Castor oil is not only compatible with, but will plasticise a wide variety of natural and synthetic resins, waxes, polymers and elastomers. (CasChem, 2020) Castor oil maintains higher viscosity even at high temperatures and liquid at low temperatures. Due to its’ non-drying nature, it is regarded as one of the best industrial lubricants.
Patel et al (2016) further state:
"The hydroxyl functionality of RA makes the castor oil a natural polyol providing oxidative stability to the oil, and a relatively high shelf life compared to other oils by preventing peroxide formation. The presence of the hydroxyl group in RA and RA derivatives provides a functional group location for performing a variety of chemical reactions including halogenation, dehydration, alkoxylation, esterification, and sulfation. As a result, this unique functionality allows the castor oil to be used in industrial applications such as paints, coatings, inks, and lubricants.20" (Patel et al, 2016)
The oil is rich in omega-6 and omega-9 fatty acids along with Vitamin E which makes it perfect to be used as a nourishing and hydrating agent. Bioactive compounds like vitamin E and other tocopherols make it an effective antioxidant and anti-inflammatory agent as well. Castor oil and its related ingredients are extensively used in the formulation of many different cosmetics and personal products including skin-care products, soaps, and lipsticks.
Traditional and Non Cosmetic Uses
Castor oil has been used as a laxative for thousands of years. It works by stimulating the muscle in the colon, encouraging peristalsis. It also hydrates the gut (drawing moisture to the lower bowel) which soften stools, reducing straining and improving symptoms. Interestingly, it ricenoleic acid also stimulates the uterus by the same mechanism. (10)
As mentioned previously, it has also been used traditionally for eye problems (9), as eye drops and problems around the eyes.
Derivatives
Castor oil is the starting point for a number of chemicals, notably sebacic acid, undecylenic acid and nylon-11. It is used to make various grades of hydrogenated vegetable oil and sulfonated castor oil, known as Turkey Oil. It is also used to synthesis C7 aldehyde (Jasmine type aroma) used in washing powders, soaps, candies and perfumes.(5)
Its sodium and potassium soaps are emulsifiers and foam stabilizers. It is used in manufacturing poly glycerol poly ricinoleate (PGPR), an emulsifier used in the production of chocolate (and used in cosmetics.)
Fatty Acid Composition
Cosmetic Use
Castor oil is well-known for its strong anti-inflammatory and anti-bacterial properties making it an ideal substance to heal and cleanse damaged skin (9). These features make it a well-rounded beauty oil. As such, it has been safely used in well over 900 cosmetic products (2). Following are the most beneficial aspects of using castor oil:
Acne and Anti-inflammatory Skin Conditions
Acne is caused by the overgrowth of inflammation-causing bacteria such as Propionibacterium acnes and Staphylococcus aureus. The antimicrobial properties of ricinoleic acid may help counteract this imbalance (6).
Castor oil is well known for its anti-inflammatory properties so may be useful against eczema, dermatitis, psoriasis, and other dry skin conditions.
Various studies have investigated its use in treating blepharitis (red, swollen, inflammed eyelids of unknown causes). One study by Muntz et al (2020) evaluated the effects of tropical castor oil application to the eyelids of patents with blepharitis. The participants (14 female and 12 males) were asked to apply 100% cold pressed castor oil to the lid of one eye twice daily for 4 weeks. Ocular surface characteristics, symptoms, and tear film parameters were assessed at baseline and day 28. The study found there to be ‘significant’ clinical improvements in the eye treated with castor oil as opposed to the control. This included a reduction in eyelash matting, telangiectasia (thread veins), madarosis (eyelash loss), cylindrical dandruff and greater decreases in staphylococcal.” They concluded that, ”The favourable therapeutic profile would suggest that castor oil demonstrates promise as a potential treatment for blepharitis.”
Ricinoleic acid the main fatty acid component of castor oil may help reduce pain and swelling. According to a study, the application of a gel containing ricinoleic acid led to a greater degree in pain reduction as compared to other methods (7).
An Effective Moisturiser
Castor oil can inhibit trans-epidermal water loss, thus moisturising the skin. It forms an effective barrier to the environment helping maintain optimum skin hydration.
Ormsby and Montgomery (1954 ) describe castor oil as one of the "nutritive and soothing oils" which may be used by direct application or through saturated compresses to the skin. “These are frequently used for the removal of crusts and scales.(1970)” It is for this reason you will find them in soothing zinc and castor oil ointments.
Penetration Enhancer
In a recent study, researchers prepared an analgesic gel using castor oil. They prepared gels with 1%-5% castor oil and found that ‘castor oil had an effective enhancement for permeation [in-vitro) …with the higher concentration of the oil were significantly (P<0.05) enhanced penetration of the drug through the membrane.’ Therefore castor oil may be a natural penetration enhancer for active skincare ingredients (6).
Formulating with Castor Oil
Use castor oil in formulations for dry and irritated skin conditions. Traditionally it has been used in zinc and castor oil nappy / dry skin creams and in lip care products, adding shine and emolliency. Use it in balms and creams to increase stability. In old time lip sticks the use of high levels of waxes and castor oil resulted in shrinkage whilst cooling. This allowed for easy removal from the mould (8)
In cold processed soap making it gives a certain degree of transparency to soap and is a foam stabiliser. However, it is not advisable to use more than 5% as it can contribute to a loss in viscosity (soft soap). I tend to use it at no more than 3-4%.
Use castor oil to disperse pigments before adding to the formula. Use castor oil to increase viscosity of oils and cleansing oils; the thickening properties are resistant to fluctuations in temperature.
References
Kelly, Anthony J (1996). Cochrane Database of Systematic Reviews || Castor oil, bath and/or enema for cervical priming and induction of labour doi:10.1002/14651858.CD003099.pub2
Patel VR, Dumancas GG, Kasi Viswanath LC, Maples R, Subong BJ. Castor Oil: Properties, Uses, and Optimization of Processing Parameters in Commercial Production. Lipid Insights. 2016 Sep 7;9:1-12. doi: 10.4137/LPI.S40233. PMID: 27656091; PMCID: PMC5015816.
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. International Journal of Toxicology, 26(), 31–77. doi:10.1080/10915810701663150 (2007)
Al-Mamun, M. Abdulla; Akter, Zerin; Uddin, Md Josim; Ferdaus, K. M. K. B.; Hoque, K. M. F.; Ferdousi, Z.; Reza, M. Abu (2016). Characterization and evaluation of antibacterial and antiproliferative activities of crude protein extracts isolated from the seed of Ricinus communis in Bangladesh. BMC Complementary and Alternative Medicine, 16(1), 211–. doi:10.1186/s12906-016-1185-y
Ramanjaneyulu, Anumula & Anudradha, G & Venkata Ramana, Maparla & Vishnu, A & Reddy, Vardhan & Gopal, N. (2018). Multifarious Uses of Castor (Ricinus communis L.).
Alaayedi, Maryam & Mahmood, Hasanain & Saeed, Ashti. (2018). The enhancement effect of castor oil on the permeability of flurbiprofen as transdermal gel. International Journal of Applied Pharmaceutics. 10. 140. 10.22159/ijap.2018v10i1.23348.
Boddu, Sai H.S.; Alsaab, Hashem; Umar, Sadiq; Bonam, Sindhu Prabha; Gupta, Himanshu; Ahmed, Salahuddin (2015). Anti-inflammatory effects of a novel ricinoleic acid poloxamer gel system for transdermal delivery. International Journal of Pharmaceutics, 479(1), 207–211. doi:10.1016/j.ijpharm.2014.12.051
Rosen, et al (2014) Harry’s Cosmeticology, Chemical Publishing
William A. McGarey, M.D (1970) Edgar Cayce and the Palma Christi, Edgar Cayce Foundation
Arslan GG, Eşer I. An examination of the effect of castor oil packs on constipation in the elderly. Complement Ther Clin Pract. 2011 Feb;17(1):58-62. doi: 10.1016/j.ctcp.2010.04.004. Epub 2010 May 18. PMID: 21168117.