

Written by: Billie A. Leyendecker:

Aromatic Scholars Program Graduate with The School for Aromatic Studies

Introduction

Prickly pear seed oil interests me a great deal. I recently became aware of the health benefits it has for skin, and so I decided to research this topic a bit further. My interest stems from the fact that I grew up in South Texas where prickly pear cactus grows abundantly. It is actually the state plant of Texas.

Everywhere I looked, the cactus grew. Observing its spine-covered, prickly exterior and knowing it grew wild out in the hot, dry, and rugged pasture, I never imagined it could possibly benefit the delicate nature of human skin. I come from a long line of ranchers and farmers, and I remember witnessing my uncles and Father burning the thorns off of the prickly pear cactus. The thorns were burned off to enable cattle to feed during times of drought. The cactus provided a food and water source when hay and water were scarce. Other than that, and the fact that you could eat nopales con huevo (the Mexican name for cactus with eggs), or drink a prickly pear margarita, I was not familiar with any other uses for the cactus. So, it was quite a surprise for me to learn that the prickly pear cactus is quite beneficial for human skin. I became fascinated by this revelation and wanted to learn more.

As I began my research, I questioned what particular parts of the plant may be used in skincare. Prickly pear cactus, or Opuntia ficus-indica (L.) Mill., is also referred to as barbary fig and is a member of the Cactaceae family. The parts of the plant include pads (also called leaves or cladodes) covered with spines, fruits (or tunas), seeds, flowers, and stems/trunks. The fruits range in color and can be green, yellow, orange, or red. The flowers of the prickly pear cactus can also range in color, even among the same species. Flowers can either be yellow, red, or purple.

Image credit: http://www.botanical-online.com/english/prickly_pear_cultivation.htm

History

Most of the plant parts benefit humans and animals both internally and externally and have been used throughout the world. For instance, in traditional medicine, Opuntia ficus indica has been used for the treatment of burns. The Aztecs extracted the milky juice from the plant and mixed it with honey and egg yolk to provide an ointment to treat burns. Prickly pear cactus has been used for wounds, edema, hyperlipidemia, obesity and catarrhal gastritis. In Mexican traditional medicine, prickly pear cactus (nopal) is used for the treatment of diabetes and high cholesterol. Alcoholic extracts have been indicated for anti-inflammatory, hypoglycemic, and antiviral purposes. The Chinese dressed abscesses with the fleshy pad of the plant. The American Indians used the fruit for food and also made syrup from it to treat whooping cough and asthma.

Only recently, research has begun to show just how much the seeds of the prickly pear can so greatly benefit skin. Within the edible part of each prickly pear fruit there are numerous seeds. The seed amount can vary from 30% to 40% on a dry weight basis. These seeds contain oil, and it is this nutrient-rich oil that is extracted and then used on the skin. Today, oil can be pressed from the seeds and then used as a carrier oil or ingredient in cosmetics and skincare applications.

Anatomy of the Skin’s Epidermis

The epidermis, or outermost layer of human skin, is covered and protected by a layer of lipids and sweat known as the acid mantle. The lipid portion of the acid mantle is made up of sebum from sebaceous glands as well as lipids from the stratum corneum (the outermost layer of the epidermis) The sweat of the acid mantle is that secreted by sweat glands. The acid mantle has an acidic pH. The pH is the measurement of acidity or alkalinity of a body fluid. With a pH between 4 and 6.5, the skin is protected from bacterial and fungal infection as well as water loss. The acid mantle also supports the barrier function of the stratum corneum. If the acid mantle loses its acidity, the skin becomes susceptible to damage and infection as well as irritation and sensitivity.

The stratum corneum has a brick-and-mortar type design. Corneocytes are the cells that form the brick-like layer. The mortar is made up of a complex of intercellular lipids that holds the moisture in between the corneocytes. The stratum corneum maintains the water level of the skin below and controls and reduces what is known as transepidermal water loss (TEWL). TEWL is the natural moisture flow out from deeper skin layers to be lost eventually by evaporation from the skin surface. With the brick-and-mortar design, the cells in the stratum corneum (the corneocytes) form a water-retaining barrier embedded in a lipid matrix.

The principal lipids that make up the mortar of the stratum corneum include ceramides (approximately 40-50%), cholesterol (20-25%), and fatty acids (10-25%). It is this mortar of lipids that serves to prevent water loss through the stratum corneum. These lipids and the natural moisturizing factor (NMF) of the stratum corneum are crucial in maintaining the water level of the skin as well as reducing TEWL. The NMF, which is housed within the corneocytes, is composed of free amino acids and their derivatives, urocanic acid, inorganic salts, sugars, lactic acid, and urea. NMF components are highly efficient humectants that attract and bind water from the atmosphere, drawing it into the corneocytes. These compounds are responsible for keeping the skin moist and pliable by attracting and holding water. They can hold large amounts of water in the skin cells and are also capable of absorbing water from the atmosphere and/or products applied to the skin. The lipids serve to prevent water loss from occurring in the NMF.

The Stratum Corneum Skin Barrier Function – Normal versus Dry Skin

Fatty acids in the skin lubricate, soften, and protect skin and prevent moisture loss from the skin. Both essential and non-essential fatty acids play separate and critical roles in proper skin function. The two types of essential fatty acids (EFAs) are linoleic acid and alpha-linoleic acid. EFAs are called essential because they are absolutely essential in our bodies, but our bodies cannot synthesize them. We must, therefore, consume them in our diets or apply them to our skin. All other fatty acids found in the skin simply are referred to as fatty acids. These include palmitic acid, oleic acid, myristic acid, stearic acid, and others. Non-essential fatty acids can be produced by the body, although they can still be ingested from some of the food that we eat or applied to the skin.

Components of Vegetable/Herbal/Nut/Seed Oils and Their Effect on Skin

A deficiency in stratum corneum lipids may contribute to dehydrated skin or xerosis (an abnormal dryness of the skin or mucus membranes). Factors that may cause such condition include age, low humidity in the environment, cold or heat exposure (e.g. sunburn, wind burn, or frostbite), diet, genetics, and indoor heating. Factors that can break down the protective lipid layer and increase TEWL include taking long, hot showers in the wintertime, using harsh detergents or solvents, excessive hand washing, and applying irritating chemicals. When the skin barrier breaks down, one may notice dry, itchy, flaky, rough, and dull skin and can even develop fissures and cracks. Whether a person has healthy, supple skin or suffers from common skin disorders, maintenance of a healthy skin barrier is vital. A daily skin regimen must be followed regularly to maintain the health of the skin.

One exceptional way to help maintain the health of the skin is to apply vegetable/herbal/nut/seed oils onto the skin. These oils, along with creams, lotions, ointments, butters, and balms soften and smooth the skin surface, maintain skin’s tone and elasticity, prevent TEWL, and support the lipid matrix. Vegetable and seed oils, beeswax, squalene, lanolin, and shea butter supply nutrients to and have a hydrating effect on the skin. They are called occlusive substances and form a barrier on the surface of the skin helping to reduce TEWL. Thus, vegetable oils are highly biocompatible to the skin and maintain the health of the stratum corneum.

Vegetable oils can be used to dilute and carry essential oils onto skin. They can also be therapeutic substances, in that they contain the following chemical components: 1.) essential and non-essential fatty acids, 2.) fat-soluble vitamins, 3.) sterols/phytosterols, and 4.) polyphenols/phenolic compounds.

Component 1 – Essential and Non-Essential Fatty Acids: Vegetable oils contain varying amounts of EFAs and non-essential fatty acids. When EFAs are deficient in the skin, the integrity of the skin suffers. A deficiency can cause a disruption in the epidermic homeostasis which affects the barrier function of the skin. This can then lead to TEWL which can then lead to skin disorders such as dryness, scaliness, redness, dermatitis, and other signs of inflammation. Diet, age, and certain diseases like diabetes contribute to an EFA deficiency. The EFAs present in vegetable oils help restore the skin barrier and treat inflammatory disorders of the skin including dermatitis, psoriasis, and eczema. They help wounds heal and help in the prevention of wrinkles.

As mentioned earlier, linoleic acid (LA) is one of the two types of EFAs. LA, the most abundant polyunsaturated fatty acid (PUFA) is present in the epidermis. PUFAs are fatty acids with two or more carbon double bonds. They include omega 3 and omega 6 fatty acids. They are very unstable and readily oxidize when exposed to oxygen and light. When tocopherols such as Vitamin E are present in a PUFA-rich vegetable oil, the oil’s lipids become more stable. Linoleic acid, an omega 6 fatty acid, is an essential fatty acid in the skin that is required for the formation and maintenance of the cutaneous barrier to water loss. If the water content of the stratum corneum (commonly caused by a breakdown or assault to the skin barrier) falls below 10% the natural functions of it are impaired and the skin becomes dry (dehydrated), scaly, and less pliable, all the signs of xerosis. The most common areas individuals experience xerosis are on the arms and legs. Linoleic acid is crucial to the proper growth and development of the epidermis. It also is required for synthesis of the important long-chain ceramides necessary to protect against dry skin. Vegetable oils rich in linoleic acid include: safflower, sunflower/not high oleic acid version, flax seed, hemp seed, wheatgerm, walnut, and sesame oil. Macadamia nut and sea buckthorn oils are all rich in palmitic acid. The other type of essential fatty acid found in vegetable oils is known as alpha-linoleic acid (ALA). It reduces inflammation when applied topically and can reduce acne.

Component 2 – Fat-soluble Vitamins: Vitamin E, or tocopherols, is a potent antioxidant found in vegetable oils. Antioxidants prevent free radicals from causing cell damage. Skin is susceptible to aging from free radicals because the free radicals damage the collagen (the main component in connective skin tissue) and elastin fibers in the skin. Tocopherols function as free radical scavengers. Vitamin E helps heal, repair, and regenerate skin. There are several types of tocopherols including alpha (α), beta (β), gamma (γ), and delta (δ) tocopherols. Vegetable oils are also a good source of fat-soluble vitamins A, D, and K. As stated above, when tocopherols such as Vitamin E are present in a PUFA-rich vegetable oil, the oil’s lipids become more stable.

Component 3 – Sterols/Phytosterols: Phytosterols are components found in vegetable oils that resemble cholesterol components. Like cholesterol, phytosterols have a water-binding capacity that may help maintain a healthy skin barrier function. When phytosterols are applied topically on the skin, anti-aging benefits may occur. They not only stop the slow-down of collagen production caused by sun damage, but they can also encourage new collagen production.

Component 4 – Polyphenols/Phenolic compounds: Polyphenols are found in vegetable oils and are a large class of chemical compounds known as phenolic compounds. Whether ingested or applied topically, they provide the body with antioxidant, anti-inflammatory, anti-carcinogenic, and oxidative stress prevention. Polyphenols prevent skin damage from sunlight’s UV rays and can ameliorate adverse skin reactions following UV exposure including skin damage, erythema (redness or rash resulting from capillary congestion), and lipid peroxidation (oxidative deterioration of lipids).

Components of Opuntia ficus indica Seed Oil

Image credit: https://en.wikipedia.org/wiki/Opuntia#/media/File:Prickly_Pear_Closeup.jpg

So, what are the precise chemical components found in prickly pear seed oil that so greatly support the health and texture of the skin? Cactus pear oil was examined in a 2002 study conducted by Mohamed Fawzy Ramadan and Jorg-Thomas Morsel where total lipids were found to be 98.8g/kg dry weight. In the study it was found that the fatty acid profile of seed oil evinces the lipids as a good source of the essential linoleic acid and oleic acids, wherein the ratio of linoleic to oleic was about 3:1. Linoleic was the dominating fatty acid, followed by palmitic and oleic acid, respectively. Ramadan and Morsel suggested that the levels of total lipids may depend on fruit cultivar, degree of ripeness, and fruit processing and storage conditions. As for fat-soluble vitamins, Ramadan and Morsel found a Vitamin E level of 0.04% of total lipids in the seed oil. γ-tocopherol was the main form of Vitamin E found, followed by α-tocopherol. Vitamin A in the form of β-carotene accounted for less than 0.42g/kg in seed oil. Vitamin K 1 was also present at 0.05% of total lipids. Also, hi levels of sterols were estimated for the seed oil, which made up 9.33g/kg of seed oil. β-Sitosterol was the sterol marker, which comprised 72% of the total sterol content in the seed oil. The next major component was campesterol. Stigmasterol, lanosterol, ∆5-avenasterol, and ∆7-avenasterol were also found. The study concluded that prickly pear seed oil, as well as prickly pear pulp oil is a rich source of fatty acids, fat-soluble vitamins, and sterols. Much of the research conducted in the years following this study referred back to and compared their data and results with those of Ramadan and Morsel.

Other studies also found prickly pear seed oil to be exceptionally rich in fatty acids, particularly in linoleic acid. One study measured between 61.4 – 68.9% linoleic, 12.38 – 16.51% oleic, and 11.44 – 15.89% palmitic acid. In yet another study, of the total fatty acids present in the seed oil, 70.3% consisted of linoleic, followed by 16.7% oleic. With regard to its lipid profile, Opuntia seed oil was considered exceptionally rich and comparable with grape seed oil. One other study examined and compared the seed oils of two species of prickly pear which were Opuntia ficus indica and Opuntia dilenii. It found exceptional linoleic acid levels of 58.79 and 79.83%, respectively. There was also a study that tested four different colored fruits and the seed oils of each. Red, orange, yellow, and green fully ripened fruits were picked in August and then tested. The level of linoleic acid in one color of fruit did not necessarily mean relatively similar levels of other fatty acids. For example, while linoleic levels ranged from greatest to least as 63.1% for orange, 62.1% for yellow, 61.8% for green, and 58.7% for red, oleic levels ranged from greatest to least as 24.3% for red, 20.9% for yellow, 16.3% for green, and 15.2% for orange.

A 2014 study found that the prickly pear seed contained 403 mg/kg of Vitamin E mostly in the form of γ-tocopherol. Some studies considered the tocopherols in the seed oil to be capable of making the seed oil quite stable. One of these is the study mentioned above where the seed oils of Opuntia ficus indica and Opuntia dilenii were compared. Although the levels of γ-tocopherol found in the two seed oils were only 1.23% and 0.29% of the total lipids respectively, the study still stated, “High levels of Vitamin E, detected in the oils, may contribute to great stability toward oxidation.”

A German study focused on topical treatments containing phytosterols. The results indicated that phytosterols not only stopped the slow-down of collagen production, but they actually encouraged new collagen production. Thus, the researchers suggested that phytosterols can reverse the effects of aging and may be useful additions to anti-aging products. In the study mentioned earlier that compared the seed oils of Opuntia ficus indica and Opuntia dilenii, the sterolic fraction was composed of β-sitosterol 21.93% and 2.80%, campesterol 3.75% and 0.51%, stigmasterol 1.64% and 0%, and fucosterol 0% and 0.27% respectively. The sterol marker, β-sitosterol, accounted for 80.27% and 78.21% of the total sterol content in Opuntia ficus indica and Opuntia dilenii seed oils. These numbers were similar to those found in the Ramadan and Morsel study.

Polyphenols are abundant in the cactus pear. The growing interest in polyphenols results from their antioxidant potential which is involved in health benefits such as the prevention of inflammation, cardiovascular dysregulation, and neurodegenerative diseases. Polyphenols are free radical scavenging and have also proven anticancer activity. All parts of the cactus plant are rich in members of the polyphenol family such as various flavonoids and phenolic acids. Prickly pear seeds contain high amounts ranging from 48 (red) to 89 (orange) mg/100 g and include feruloyl derivatives, tannins, and sinapoyl diglucoside. In the study that examined the four different colored cactus fruits, the phenolic profile of the seeds displayed a high complexity, with more than 20 compounds detected at 330 nm after liquid chromatography separation. Among them, three isomers of feruloyl-sucrose were firmly identified and so was sinapoyl-diglycoside. High correlations were found between phenolic content in the defatted seed extracts and their antioxidant activity. The seed extract of the orange fruit showed significantly higher values for all of the detected phenolic compounds. The samples presenting the highest antioxidant activities also had the highest phenolics, tannins and flavonoids content. Indeed, the seed extract of the orange fruits presented better activities, while the extract from the red one showed lower ones.

One other thing to note about prickly pear seeds is that although cactus pears carry an average of 150-300 seeds each, only a tiny amount of oil can be extracted from each seed. This, in turn, makes the cost of prickly pear seed oil extremely high. At about $2,000 per liter (approximately 34 US fluid ounces), prickly pear seed oil is the most expensive carrier oil on the market. According to Karim Anegay, who heads the cactus program at the Economic Promotion Office in Morocco, 8 tonnes of cactus pears are needed to produce just 1 liter of seed oil.

Conclusion

After researching the components of prickly pear seed oil, it is quite easy to see why it is gaining such popularity in the cosmetics and food industries. With large amounts of linoleic acid, Vitamin E, phytosterols, and polyphenols, prickly pear seed oil stimulates healthy cell production and turnover, provides protection, and helps skin retain moisture. These components make the oil an extremely rich and skin-nourishing oil. It soothes, hydrates, and reduces inflammation that can damage collagen, and it can prevent skin aging and wrinkles. The only disadvantage I can see is the cost to extract, press, and bottle the oil. However, after the research I conducted, I realize that prickly pear seed oil’s cost may be worth every drop.

References

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Image by: Prickly Pear