The moisturising effects of avocado oil

Ancient civilisations have always been nature worshippers. Trees that were revered usually had some component with medicinal and curative properties. The avocado has been considered sacred by Native Mesoamericans from ancient times. The remarkable properties of the fruit, recognised since millennia are now being analysed by systematic scientific methods. The skin improving properties of avocado has been distilled into its oil and is an ingredient in the griffin+row’s Nourish and Enrich. It is interesting to know how this native of Central America has become such an important name in the diary of the skin care specialist.

Introducing Perseaamericana– the avocado

The thick bumpy peel of the avocado may have given it the name of alligator pear, but the botanical name of the avocado is Perseaamericana. The fruit was known to Europeans since the 16th century and Carolus Linnaeus had classified it under the genus Laurus. The family Lauraceae includes several tropical and semi-tropical trees that resemble the avocado. In 1754, with the definition of the clade of Laurace flora that belonged to the Americas, Miller placed the avocado under the genus Persea and (given its habitat) the species name of americana1.Some botanists also called the fruit Perseagratissima because of its unique aroma and taste.

The common name of the fruit comes from the Aztec name ‘auacatl‘. This name means ‘testicle’ and alludes to the shape of the fruit and the fruiting pattern – the fruit is always found in pairs- as well as its aphrodisiac qualities. The word ‘auacatl’ was corrupted by the Spanish into ‘aguacate’ which became the English ‘avocado’2.

The avocado is thought to have originated in Peru some 10,000 years ago. The oldest evidence of the cultivation of the avocado comes from the Caral civilisation of the Supe valley (circa 3000 BC). Ethnobotanical evidence also places the use of the fruit in the Moche valley in northern Peru (circa 2500-1800 BC) and coastal Peru (circa 1500 BC) 1.

The fruit appears to have moved north to Central America where the Mokaya (circa 1500 BC) –who are the forerunners of the Olmec and Mayans- are thought to have relied heavily on the avocado for nutrition. The actual cultivation of the fruit may have commenced in Mexico in 500BC 3. On the whole the fruit is endemic to Central America and is believed to have been known to the Mesoamericans since millennia.

The Spanish came across the fruit when they conquered the Americas. Following this, cultivation of the fruit was undertaken in Florida and California in the United States, the West Indies, Indonesia and Africa. Today Mexico still contributes about 45% of the total avocado cultivation. South and Central American countries like Chile, Dominican Republic, Colombia, Brazil and Peru and the United States are major contributors to the global avocado market. Indonesia is perhaps the only country outside the Americas to have appreciable avocado cultivation.

Traditional uses of Avocado

The earliest evidence of the use of avocados is dated to between 9000-10,000 years ago in the Tehuacan valley in Peru. It has also been found in the archaeological sites of the Caral civilisation in the Supe valley and the Moche Valley at Caballo Muerto about 4500-3800 years ago. Since then, the avocado has made its appearance at several archaeological digs. It has also been recovered from Inca settlements where it was interred in royal sarcophagi 1,4.

For the Mayans, the avocado was a sacred fruit. It has been found to be associated with iconography dating from the Classic period (300 AD –900 AD).The glyph for the fourteenth month in the Mayan calendar is represented by the glyph for the avocado, called K’an kin. The glyph was also the state emblem of the Classic Mayan city of Pusilha (in present day Belize), which was called the ‘Land of Avocado”. Mayan ancestors were thought to be reborn as trees. And so the sarcophagus of the King Janaab Pacalhas sees the Lady KanalIkal emerging as an avocado tree from it. This actually dates the cultivation of the fruit since tree representations on sarcophagi referred to sacred trees4.

North of the Mayan territory, the Aztecs of Mexica referred to the avocado as ahuacatl in the Nauhatl language. A Mexica city was even named “Ahuacatlan” as the place where the avocado is plentiful.

The introduction of the avocado to the Europeans was in the late 16th century when the Spanish King Felipe asked for a description of the avifauna of the ‘New Spain’ in the Americas. Francisco Hernandez mentioned the avocado in his ‘Historia de las plantas de la Neuva Espana’ as an oak-like tree with black coloured fig-like fruit and leaves with a distinct smell of anise 1.

In Central American-Indian folk medicine, the fruit was more than just a source of nutrition. It was recommended for strengthening bones, improving vision and in the prevention of headaches and neuralgia. Even minor ailments such as cold, catarrh, cough and abdominal bloating were treated with the fruit. Avocado oil was applied to joints afflicted by rheumatism and gout 4. The astringent properties of the fruit were believed to repair the chambers of the heart 1.

Healthy individuals used the fruit as a tonic to stimulate the appetite, invigorate the nervous system and regulate menstruation 5. On the cosmetic front, the fruit was used to repair split ends of hair.

The fruit was also fed to animals in order to improve the flavour of their meat1.

Other than the fruit, the leaves of the avocado which have been described to be warm and dry were used in lavatories. The seed was also used medicinally in order to soothe and cure bruises on the soles of the feet 1.

In modern times, avocado has become the foodie’s favourite and is used in guacamoles, smoothies and ice creams. It is even used as a substitute for mayonnaise in sandwiches and butter in baked items. Of course, the fruit is also eaten with a sprinkling of salt or sugar 2.

Bioactivity and associated components of the plant

The avocado fruit is edible for humans, and the seeds, leaves, and bark are considered medicinal4.

The fruit is especially rich in unsaturated fatty acids. The fruit pulp contains-

  • Saturated fatty acids: Palmitic acid (12.2%), myristic acid, stearic acid and arachidic acid (in trace amounts).
  • Unsaturated fatty acids: MUFAs: Palmitoleic acid (4.6 %) and oleic acid (72.8 %)

PUFAs: Linoleic acid (10.6%), linolenic acid (<1 %) and arachidonic acid (<1%)

  • Vitamins: Fat soluble vitamins A, D and E. The tocopherol (vitamin E) in avocado is α-tocopherol is present in significant amounts (3%). Among the B vitamins thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid, biotin are present in trace amounts.
  • Minerals: Potassium, phosphorus, manganese and silicon are present in. Calcium and sodium in appreciable amounts and iron and boron in smaller quantities5.
  • Phytosterols: Avocado is one of the richest fruit sources of phytosterols6. The phytosterols in avocado include β-sitosterol, campesterol and stigmasterol.

Avocado pulp is the source of avocado oil. The percentage of oil is related to the moisture content of the fruit. Usually, the fruit is harvested when the oil content is approximately 8%. The fruit is skinned, stoned and the pulp is partially dried. The oil is then extracted using steam distillation. Due to the presence of chlorophyll, the raw oil appears to be a greenish-yellow colour. This is decolourised using activated earth, deodorised (if necessary) and ‘winterised’ by the addition of oxystearin7

Oleic acid and α-tocopherol: a look at the active constituents

  •  Oleic acid is a monounsaturated fatty acid.

Oleic acid is the most widely occurring unsaturated fatty acid in nature. It is also important in keeping the elasticity and flexibility of skin8.

  • α-Tocopherolis one form of the fat- soluble vitamin E.

It is a potent antioxidant and prevents free radical formation in the cell membrane which can cause damage to the tissue. For its membrane stabilising properties, it is included in skin care formulations 9.

Benefits and uses of avocado oil

Avocado oil is generally not used for cooking since it develops a slightly bitter taste with mild heat. It can however be consumed raw and has been found to have some cholesterol lowering properties 10. The skin care industry has found the oil immensely useful for the following reasons-

  • Moisturising activity: Dry and ageing skin is characterised by a rough texture and low flexibility. This is due to a diminished supply of fatty acids that help in keeping pace with the keratinisation that keeps the skin in good repair. Fatty acids such as stearic, linoleic, oleic and lauric acids act as emollients that help to repair the skin and improve skin permeability. Avocado oil not only contains these oils but also has phytosterols that act as emulsifiers and keep the trans-epidermal water loss under control. Vitamin E (α-tocopherol) in avocado oil also helps to retain water in skin, adding to the moisturising action1011.
  • Anti-ageing activity: The unsaponifiable fraction of avocado oil delays the formation of wrinkles by restructuring the collagen of ageing skin 10.
  • Antioxidant activity: The lipoperoxides formed in cell membranes due to radiation and chemicals results in cellular damage that is seen as ageing of the skin. The presence of tocopherol in avocado oil makes it an effective free radical (peroxide) scavenger. This translates to an anti-ageing activity.
  • Wound healing: Studies on laboratory animals have shown that avocado oil is an effective in healing burns and wounds 10.
  • Repair of scars: Avocado oil has a lysyl oxidase inhibitory activity which prevents the formation of excess collagen in scar tissue. Application of the oil initiates skin restructuring which ensures that the tough scar tissue formed on an injury is softened and blends with the complexion 11.
  • Sunscreen effect: Avocado oil is known to have a protective effect against UV radiation from sun rays, making it a good sunscreen7.
  • Anti-inflammatory effects: The unsaponifiable fraction of avocado oil is known to inhibit prostaglandin E2, cytokine and metalloproteinase production in cultured chondrocytes11.
  • Anti hair-loss: Because it is rich in linoleic acids, avocado oil is recommended to reverse hair loss. Linoleic acid containing oils are useful in topical applications to treat alopecia, depigmentation and damaged hair 5.

Botany and grow it yourself

The avocado belongs to the Lauraceae family. The tree grows to a height of 8 to 12m. The stem is erect and the exterior bark has a rough texture. The top of the tree sprouts a number of branches. The dark green leaves are alternate and oval in shape. Yellow-white coloured flowers bloom in clusters at the axillary branches. The fruit is pear- shaped and grows in pairs.  Depending upon the variety, the skin of the fruit can be either thin or thick but all varieties have bumps on them. The colour of the fruit can range from green to yellow or purple. The pulp is yellow and when ripe, has the consistency of butter. A large spherical seed is enclosed in the fruit 5.

There are now three main varieties of Avocado- Mexican, Guatemalan, West Indian. They differ in the size of the fruit, the colour and texture of the skin and the amount of pulp contained in the fruit. The most popular variety grown in USA is the Haas which has been selected for optimum pulp and taste. Also, since the skin is sufficiently thick, it does not require extra packaging and has a good shelf life.

The tree can be grown well from the seed which can be sprouted into a seedling before being planted in loose, coarse soil and placed in a warm place. The seedling requires intermittent sunlight and occasional watering. Once the seedling has grown to a height of two feet, it can be potted in a container that is 3 feet wide and 3 feet deep. The sapling needs sunlight and moderate watering to grow into a sizeable tree. It takes at least 5 years for the tree to start bearing fruit 12.

Glossary

Phytosterol: Phytosterols are the sterols found in plants just as cholesterol is found in animals. Phytosterols in the diet can reduce circulating cholesterol levels in humans.

Emollient: Any substance that soothes and softens the skin is classified as an emollient.While creams and lotions that are emulsions of oil and water make good emollients, vegetable oils can also be used directly for the same purpose. Moisturisers are also emollients.

Winterisation: Winterisation is a process that refers to preparing a product for lower temperatures.In the case of vegetable oils, this involves removing high melting point substances such as waxes and triglycerides from the oil by heating and slow cooling. Winterisation is generally done for salad oils.


References

  1. Galindo-Tovar ME, Arzate-Fernández AM, Ogata-Aguilar N, Landero-Torres(2007). The Avocado (Persea Americana, Lauraceae) Crop in Mesoamerica: 10,000 Years of History. Harvard Papers in Botany12(2): 325- 334.
  2. Fillippone PT. (2017). Avocado history- from Aztec aphrodisiac to American obsession. Retrieved from https://www.thespruce.com/history-of-avocado-1807562 (1st September 2017).
  3. The history of California avocado. (2017), Retrieved from https://www.californiaavocado.com/the-california-difference/avocado-history (1st September 2017)
  4. Landon AJ. (2009). Domestication and significance of Perseaamericana, the avocado, in Mesoamerica. Nebraska Anthropologist 47: 62-81.
  5. Avocado oil.(Undated).Retrieved from http://www.centerchem.com/Products/DownloadFile.aspx?FileID=6558 (2nd September 2017).
  6. Dreher ML and Davenport AJ. (2013). Haas avocado composition and potential health benefits. Critical Reviews in Food Science and Nutrition 53:738–750
  7. Human TP. (1987). Oil as a byproduct of the avocado. South African Avocado Growers’ Association Yearbook 10:159-162.
  8. National Center for Biotechnology Information. PubChem Compound Database; CID=445639, https://pubchem.ncbi.nlm.nih.gov/compound/445639 (accessed Sept. 4, 2017).
  9. National Center for Biotechnology Information. PubChem Compound Database; CID=14985, https://pubchem.ncbi.nlm.nih.gov/compound/14985″ rel=”nofollow”>https://pubchem.ncbi.nlm.nih.gov/compound/14985 (accessed Sept. 4, 2017).
  10. de Oliveira AP,de Souza Franco E, Barreto RR,Cordeiro DP, de Melo RG,  de Aquino CMF, e Silva AAR, de Medeiros PL, da Silva TG, da Silva Góes AJ and de Sousa Maia MB. (2013). Effect of semisolid formulation of Perseaamericana Mill (Avocado) oil on wound healing in rats. Evidence-Based Complementary and Alternative Medicine : eCAM2013, 472382.
  11. Avocado (Perseaamericana). (2010). Retrieved from http://www.sigmaaldrich.com/life-science/nutrition-research/learning-center/plant-profiler/persea-americana.html (4th September 2017).
  12. Francis M. (2017). How to grow an avocado tree: guac ‘n’ roll. Retrieved from http://www.hgtv.com/outdoors/flowers-and-plants/vegetables/how-to-grow-an-avocado-tree-guac-n-roll (2nd September 2017).