Aloe vera, pronounced /ˈæloʊ ˈvɪrə/[1], also known as the true or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan.[citation needed] Aloe vera grows in arid climates and is widely distributed in Africa, India, and other arid areas. The species is frequently cited as being used in herbal medicine. Many scientific studies of the use of extracts of Aloe vera have been undertaken, some of them conflicting.[2][3][4][5] Despite these limitations, there is some preliminary evidence that Aloe vera extracts may be useful in the treatment of wound and burn healing, minor skin infections, Sebaceous cyst, diabetes, and elevated blood lipids in humans.[4] These positive effects are thought to be due to the presence of compounds such as polysaccharides, mannans, anthraquinones, and lectins.

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.[8] 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.[8][9] Like other Aloe species, Aloe vera forms arbuscular mycorrhiza, a symbiosis that allows the plant better access to mineral nutrients in soil.[10]
[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 indica Royle, Aloe perfoliata L. var. vera and A. vulgaris Lam.,[11][12] and common names including Chinese Aloe, Indian Aloe, true Aloe, Barbados Aloe, burn Aloe, first aid plant.[9][13][14][15][16] The species name vera means "true" or "genuine."[13] Some literature identifies the white spotted form of Aloe vera as Aloe vera var. chinensis,[17][18] however, the species varies widely with regard to leaf spots [19] and it has been suggested that the spotted form of Aloe vera may be conspecific with A. massawana.[20] The species was first described by Carl Linnaeus in 1753 as Aloe perfoliata var. vera,[21] 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 as Aloe barbadensis some ten days after Burman in the Gardener's Dictionary.[22]

Techniques based on DNA comparison suggest that Aloe vera is relatively closely related to Aloe perryi, a species that is endemic to Yemen.[23] 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.[24] With the exception of South African species A. striata, these Aloe species are native to Socotra (Yemen), Somalia, and Sudan.[24] The lack of obvious natural populations of the species have led some authors to suggest that Aloe vera may be of hybrid origin.[25]
[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.[11] 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 species (or sometimes identical) can be found on the two extreme sides of the Sahara: Dragon trees and Aeonium being some of the most representative examples.

The species was introduced to China and various parts of southern Europe in the 17th century.[26] The species is widely naturalised elsewhere, occurring in temperate and tropical regions of Australia, Barbados, Belize, Nigeria, Paraguay and the US[19][27] It has been suggested that the actual species' distribution is the result of human cultivation and that the taxonomy could be doubtful too.[20]