Aloe vera

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Aloe vera, also known as the medicinal aloe, is a species of succulent plant that probably originated in Northern Africa, the Canary islands and Cape Verde. Aloe vera grows in arid climates and is widely distributed in Africa and other arid areas. The species is frequently cited as being used in herbal medicine. Many scientific studies of the use of aloe vera have been undertaken, some of them conflicting.^[1][2][3][4] Despite these limitations, there is some preliminary evidence that Aloe veraextracts may be useful in the treatment of wound and burn healing, diabetes and elevated blood lipids in humans.^[3] These positive effects are thought to be due to the presence of compounds such as polysaccharides, mannans, anthraquinonesand lectins.^[3][5][6]

Description

Aloe vera is a stemless or very short-stemmed succulent plant growing to 60–100 cm (24–39 in) tall, spreading by offsets. The leaves are thick and fleshy, green to grey-green, with some varieties showing white flecks on the upper and lower stem surfaces.^[7] The margin of the leaf is serrated and has small white teeth. The flowers are produced in summer on a spike up to 90 cm (35 in) tall, each flower pendulous, with a yellow tubular corolla 2–3 cm (0.8–1.2 in) long.^[7][8] Like other Aloe species, Aloe vera forms arbuscular mycorrhiza, a symbiosis that allows the plant better access to mineral nutrients in soil.^[9]

Taxonomy and etymology

Spotted forms of Aloe vera are sometimes known as Aloe vera var.chinensis.

The species has a number of synonyms: A. barbadensis Mill., Aloe indica Royle, Aloe perfoliata L. var. vera and A. vulgaris Lam.,^[10][11] and common names including Chinese Aloe, Indian Aloe, true Aloe, Barbados Aloe, burn Aloe, first aid plant.^{[8][12][13][14][15]} The species name vera means "true" or "genuine."^[12]Some literature identifies the white spotted form of Aloe vera as Aloe vera var. chinensis,^[16][17] however, the species varies widely with regard to leaf spots^[18] and it has been suggested that the spotted form of Aloe vera may be conspecificwith A. massawana.^[19] The species was first described by Carl Linnaeus in 1753 asAloe perfoliata var. vera,^[20] and was described again in 1768 by Nicolaas Laurens Burman as Aloe vera in Flora Indica on the 6th of April and by Philip Miller asAloe barbadensis some ten days after Burman in the Gardener's Dictionary.^[21]

Techniques based on DNA comparison suggest that Aloe vera is relatively closely related to Aloe perryi, a species that is endemic to Yemen.^[22] Similar techniques, using chloroplast DNA sequence comparison and ISSR profiling have also suggested that Aloe vera is closely related to Aloe forbesii, Aloe inermis,Aloe scobinifolia, Aloe sinkatana and Aloe striata.^[23] With the exception of South African species, A. striata, these Aloe species are native to Socotra(Yemen),Somalia and Sudan.^[23] The lack of obvious natural populations of the species have led some authors to suggest that Aloe vera may be of hybrid origin.^[24]

Distribution

The natural range of Aloe vera is unclear, as the species has been widely cultivated throughout the world. It has been suggested that naturalised stands of the species occur through North Africa inAlgeria, Morocco, and Tunisia, along with the Canary and Madeira Islands.^[10] The species was introduced to China, India, Pakistan and various parts of southern Europe in the 17th century.^[25] The species is widely naturalised elsewhere, occurring in temperate and tropical regions of Australia, Barbados, Belize, Nigeria, Paraguay and the US^[18][26] It has been suggested that, like many Aloes, the species is originally from Southern Africa and that populations that occur elsewhere are the result of human cultivation.^[19]

Alternative names

In India, the plant is known as Ghritkumari(Hindi/Sanskrit: घृतकुमारी) or Gheekvar (घीक्वार) and in Pakistan, the plant is known as Quargandal and is used in Ayurvedic medicine.^[27]

In Tamil nadu, Aloe vera is known as katraazhai(Tamil: கற்றாழை) and it has also a pet name kumari. Since use of Aloe vera extends one's longevity it has that pet name. The pulp is used extensively in Siddha medicines for treating constipation, enlargement of spleen, zymotic disease, chengamaari (a type of venereal infection) etc.^[28]

Cultivation

Aloe vera can be grown as an ornamental plant.

Aloe vera has been widely grown as an ornamental plant. The species is popular with modern gardeners as a putatively medicinal plant and due to its interesting flowers, form and succulence. This succulence enables the species to survive in areas of low natural rainfall, making it ideal for rockeries and other low-water use gardens.^[7] The species is hardy in zones8–11, although it is intolerant of very heavy frost or snow.^[8][29] The species is relatively resistant to most insect pests, though mealy bugs, scale insects and aphid species may cause a decline in plant health.^[30][31] In pots, the species requires well-drained sandy potting soil and bright sunny conditions. The use of a good quality commercial propagation mix or pre-packaged "cacti and succulent mix" is recommended as they allow good drainage.^[32] Terracotta pots are preferable as they are porous.^[32] Potted plants should be allowed to completely dry prior to re-watering. During winter, A. veramay become dormant, during which little moisture is required. In areas that receive frost or snow the species is best kept indoors or in heated glasshouses.^[8]Large scale agricultural production of Aloe vera is undertaken in Australia,^[33]Cuba,^[34] the Dominican Republic, China, Mexico,^[35] India,^[36] Jamaica,^[37] Kenyaand South Africa,^[38] along with the USA^[39] to supply the cosmetics industry with Aloe vera gel.

Uses

Aloe Vera Drink 3x 1L Bottle package

[edit]Distinction between aloin and gel of the plant

Aloe vera leaves when cut exude two fluids, with differing effects and properties. The yellow/green sap predominantly exuded wherever the green surface of the leaf is cut is an irritant. This contains the latex-like compound, aloin. On the other hand, the transparent fluid exuded by the inner leaf wherever it is cut or crushed, is soothing and said to promote healing.

For successful use of the plant, it is important to ensure that any use employs the appropriate part or parts to suit the purpose.

It is also important to understand and look for this distinction in evaluating any attempt at scientific study of the plant's medical properties. Any study which does not specify which parts of the plant were used, is likely to confuse the issue, rather than to clarify. Any product which does not distinguish these may contain a mixture of both, and therefore would be likely to have compromised usefulness for most purposes where Aloe vera is commonly used.

Medicinal uses

Scientific evidence for the cosmetic and therapeutic effectiveness of Aloe vera is limited and when present is typically contradictory.^[1][2] Despite this, the cosmetic and alternative medicine industries regularly make claims regarding the soothing, moisturising and healing properties of Aloe vera, especially via Internet advertising.^{[3][40][41][42][43]} Aloe vera gel is used as an ingredient in commercially available lotion, yogurt, beverages and some desserts.^[44][45][46] Aloe vera juice is used for consumption and relief of digestive issues such as heartburn and irritable bowel syndrome. It is common practice for cosmetic companies to add sap or other derivatives from Aloe vera to products such as makeup, tissues, moisturizers, soaps, sunscreens, incense, razors and shampoos.^[44] Other uses for extracts of Aloe vera include the dilution of semen for the artificial fertilization of sheep,^[47] use as fresh food preservative,^[48] and use in water conservation in small farms.^[49]

Aloe vera juice for ingestion.

Aloe vera has a long association with herbal medicine, although it is not known when its medical applications were first discovered. Early records of Aloe vera use appear in the Ebers Papyrusfrom 16th century BCE,^[15] in both Dioscorides' De Materia Medica and Pliny the Elder's Natural History written in the mid-first century CE^[15] along with the Juliana Anicia Codex produced in 512 CE.^[44] Aloe vera is non-toxic, with no known side effects, provided the aloin has been removed by processing. Taking Aloe verathat contains aloin in excess amounts has been associated with various side effects.^[3][4][50] However, the species is used widely in the traditional herbal medicine of China,Japan, Russia, South Africa, the United States, Jamaica and India.^[3]

Aloe vera is alleged to be effective in treatment of wounds.^[4] Evidence on the effects of Aloe vera sap on wound healing, however, is limited and contradictory.^[4] Some studies, for example, show that Aloe vera promotes the rates of healing,^[51][52] while in contrast, other studies show that wounds to which Aloe vera gel was applied were significantly slower to heal than those treated with conventional medical preparations.^[53][54] A more recent review (2007) concludes that the cumulative evidence supports the use of Aloe vera for the healing of first to second degree burns.^[55] In addition to topical use in wound or burn healing, internal intake of Aloe vera has been linked with improved blood glucose levels in diabetics,^[56][57] and with lower blood lipids in hyperlipidaemic patients,^[58] but also with acute hepatitis (liver disease).^[50] In other diseases, preliminary studies have suggested oral Aloe vera gel may reduce symptoms and inflammation in patients with ulcerative colitis.^[59] Compounds extracted from Aloe verahave been used as an immunostimulant that aids in fighting cancers in cats and dogs;^[5] however, this treatment has not been scientifically tested in humans. The injection of Aloe vera extracts to treat cancer has resulted in the deaths of several patients.^[60]

Topical application of Aloe vera may be effective for genital herpes and psoriasis.^[61] However, it is not effective for the prevention of radiation-induced injuries. Although anecdotally useful, it has not been proven to offer protection from sunburn or suntan.^[62] In a double-blind clinical trial the group using an Aloe vera containing dentifrice and the group using a fluoridated dentifrice both demonstrated a statistically significant reduction of gingivitis and plaque.^[63]

Aloe vera extracts have antibacterial and antifungal activities. Aloe vera extracts have been shown to inhibit the growth of fungi that cause tinea;^[64] however, evidence for control beneath human skin remains to be established. For its anti-fungal properties, Aloe vera is used as a fish tank water conditioner. For bacteria, inner-leaf gel from Aloe vera was shown to inhibit growth of Streptococcus andShigella species in vitro.^[65] In contrast, Aloe vera extracts failed to show antibiotic properties against Xanthomonas species.^[66]

Commodity uses

Aloe vera is now widely used on face tissues, where it is promoted as a moisturiser and/or anti-irritant to reduce chafing of the nose of users who suffer hay-fever or cold.^[67] It has also been suggested that biofuels could be obtained from Aloe vera seeds.^[68]

Historical uses

Aloin was the common ingredient in OTC laxative products in the United States prior to 2003, when the FDA ruled that aloin was a class III ingredient, therefore banning its use.^[69] It should be noted that processed aloe that contains aloin is used primarily as a laxative, whereas processed aloe vera juice that does not contain significant amounts of aloin is used as a digestive healer. Manufacturers commonly remove aloin in processing due to the FDA ruling.

Culinary uses

Aloe is also used as a foodstuff. Some molecular gastronomists have begun to take advantage of its gelling properties. Perhaps most notably among these is Chef Quique Dacosta's "Oysters Guggenheim," created at El Poblet in Spain. ^[70]

Biologically active compounds

Aloe vera leaves contain a range of biologically active compounds, the best studied being acetylated mannans, polymannans, anthraquinone C-glycosides, anthrones and anthraquinonesand variouslectins.^[3][5][6]