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.
[6] 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 being pendulous, with a yellow tubular
corolla 2–3 cm (0.8–1.2 in) long.
[6][7]Like other
Aloe species,
Aloe vera forms
arbuscular mycorrhiza, a
symbiosis that allows the plant better access to mineral nutrients in soil.
[8]
[edit]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 indicaRoyle,
Aloe perfoliata L. var.
vera and
A. vulgaris Lam.
[9][10] Common names include Chinese Aloe, Indian Aloe, True Aloe, Barbados Aloe, Burn Aloe, First Aid Plant.
[7][11][12][13][14] The species epithet
vera means "true" or "genuine".
[11] Some literature identifies the white spotted form of
Aloe vera as
Aloe vera var.
chinensis;
[15][16] however, the species varies widely with regard to leaf spots
[1] and it has been suggested that the spotted form of
Aloe vera may be
conspecific with
A. massawana.
[17] The species was first described by
Carl Linnaeus in 1753 as
Aloe perfoliata var.
vera,
[18] and was described again in 1768 by
Nicolaas Laurens Burman as
Aloe vera in
Flora Indica on 6 April and by
Philip Miller as
Aloe barbadensis some ten days after Burman in the
Gardener's Dictionary.
[19]
Techniques based on
DNA comparison suggest that
Aloe vera is relatively closely related to
Aloe perryi, a species that is endemic to Yemen.
[20] Similar techniques, using
chloroplast DNA sequence comparison and
ISSRprofiling have also suggested that
Aloe vera is closely related to
Aloe forbesii,
Aloe inermis,
Aloe scobinifolia,
Aloe sinkatana, and
Aloe striata.
[21] With the exception of the South African species
A. striata, these
Aloespecies are native to
Socotra (Yemen), Somalia, and Sudan.
[21] The lack of obvious natural populations of the species have led some authors to suggest that
Aloe vera may be of
hybrid origin.
[22]
[edit]Distribution
The natural range of
Aloe vera is unclear, as the species has been widely cultivated throughout the world. Naturalised stands of the species occur in the southern half of the
Arabian peninsula, through North Africa (Morocco, Mauritania, Egypt) as well as Sudan and neighbouring countries, along with the Canary, Cape Verde, and Madeira Islands.
[9] This distribution is somewhat similar to the one of
Euphorbia balsamifera,
Pistacia atlantica, and a few others, suggesting that a dry
sclerophyl forest once covered large areas, but has been dramatically reduced due to desertification in the Sahara, leaving these few patches isolated. Several closely related (or sometimes identical) species can be found on the two extreme sides of the Sahara:
Dragon trees(
Dracaena) and
Aeonium being two of the most representative examples.
The species was introduced to China and various parts of southern Europe in the 17th century.
[23] The species is widely naturalised elsewhere, occurring in temperate and tropical regions of Australia, Barbados, Belize, Nigeria, Paraguay and the United States
[1][24] It has been suggested that the actual species' distribution is the result of human cultivation.
[17]
[edit]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.
[6] The species is hardy in
zones 8–11, although it is intolerant of very heavy frost or snow.
[7][25] The species is relatively resistant to most insect pests, though spider mites,
mealy bugs,
scale insects, and
aphid species may cause a decline in plant health.
[26][27] In pots, the species requires well-drained sandy potting soil and bright sunny conditions; however, aloe plants can burn under too much sun or shrivel when the pot does not drain the rain. The use of a good-quality commercial propagation mix or pre-packaged "cacti and succulent mix" is recommended, as they allow good drainage.
[28] Terracotta pots are preferable as they are porous.
[28] Potted plants should be allowed to completely dry prior to re-watering. When potted aloes become crowded with "pups" growing from the sides of the "mother plant," they should be divided and re-potted to allow room for further growth and help prevent pest infestations. During winter,
Aloe vera may 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.
[7] Large scale agricultural production of
Aloe vera is undertaken in Australia,
[29] Bangladesh, Cuba,
[30] the Dominican Republic, China, Mexico,
[31] India,
[32] Jamaica,
[33] Kenya, Tanzania and South Africa,
[34] along with the USA
[35] to supply the cosmetics industry with
Aloe vera gel.
Herbal Farming in Chhattisgarh: Aloe vera
Aloe vera gel being used to make a dessert.
Preparations made from the plant
Aloe vera are often referred to as "aloe vera".
[37] Scientific evidence for the cosmetic and therapeutic effectiveness of aloe vera is limited and when present is frequently contradictory.
[2][3] Despite this, the cosmetic and alternative medicine industries regularly make claims regarding the soothing, moisturizing, and healing properties of aloe vera.
[4][38] Aloe vera gel is used as an ingredient in commercially available lotions, yogurt, beverages, and some desserts,
[39][40][41] although at certain doses, it has toxic properties when used either for ingested or topical applications.
[42]
[edit]Folk medicine
[edit]Dietary supplement
Aloin, a compound found in the exudate of some
Aloe species, was the common ingredient in
over-the-counter(OTC) laxative products in the United States prior to 2003, when the
Food and Drug Administration ruled that aloin was a
class III ingredient, thereby banning its use.
[44] Aloe vera has potential toxicity, with
side-effects occurring at some dose levels both when ingested or applied topically.
[42] Although toxicity may be less when aloin is removed by processing, aloe vera that contains aloin in excess amounts may induce side-effects.
[4][5][45] A 2-year National Toxicology Program (NTP) study on oral consumption of non-decolorized whole leaf extract of
Aloe verafound evidence of carcinogenic activity in male and female rats. The NTP says more information is needed to determine the potential risks to humans.
[46][47][48]
Aloe vera juice is marketed to support the health of the digestive system, but there is neither scientific evidence nor regulatory approval to support this claim.
[49] The extracts and quantities typically used for such purposes appear to be dose-dependent for toxic effects.
[42]
[edit]Phytochemicals
[edit]Commodities
Aloe vera is now used on facial tissues, where it is promoted as a moisturiser and/or anti-irritant to reduce chafing of the nose of users suffering hay-fever or cold.
[53] 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, shaving cream or shampoos.
[39] Other uses for extracts of aloe vera include the dilution of
semen for the artificial fertilization of sheep,
[54] as a fresh food preservative,
[55] or for
water conservation in small farms.
[56] It has also been suggested that biofuels could be obtained from
Aloe vera seeds.
[57] Aloe is also used as a food substance, possibly for its gelling properties (
see image above).
[edit]Preliminary research
Aloe vera may be effective in the treatment of wounds.
[5] Evidence on the effects of its sap on wound healing, however, is limited and contradictory.
[5] Some studies, for example, show that aloe vera promotes the rates of healing,
[58][59] 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.
[60][61] A 2007 review concluded that the cumulative evidence supports the use of aloe vera for the healing of first to second degree burns.
[62] Topical application of aloe vera may also be effective for
genital herpes and
psoriasis.
[5] However, it is not effective for the prevention of radiation-induced injuries.
Gels from
Aloe vera have been compared to those derived from other aloe species and with other plants belonging to the family
Asphodelaceae.
Bulbine frutescens, for example, is used widely for burns and a host of skin afflictions.
[63] Aloe vera extracts might have
antibacterial and
antifungal activities, which possibly could help treat minor skin infections, such as
boils and benign skin
cysts and may inhibit growth of fungi causing
tinea.
[64] For bacteria, inner-leaf gel from aloe vera was shown in one study to inhibit growth of
Streptococcus and
Shigellaspecies in vitro.
[65] In contrast,
aloe vera extracts failed to show antibiotic properties against
Xanthomonasspecies.
[66]
Compounds extracted from aloe vera may act as an
immunostimulant in cats and dogs,
[50] but this treatment has not been confirmed or scientifically tested in humans.
In a
double-blind clinical trial, both the group using an aloe vera containing
dentifrice and another using a fluoridated dentifrice had a reduction of gingivitis and plaque, but no statistically significant difference was found between the two.
[70]
Other preliminary studies have evaluated whether oral aloe vera gel may affect
ulcerative colitis,
[37] but this research remains inconclusive
