''Aloe'' (; also written ''Aloë'') is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

containing over 650

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

flowering A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

succulent

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

s.WFO (2022): Aloe L. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-4000001341. Accessed on: 06 Nov 2022 The most widely known species is '' Aloe vera'', or "true aloe". It is called this because it is cultivated as the standard source for assorted pharmaceutical purposes. Other species, such as ''

Aloe ferox ''Aloe ferox'', commonly known as bitter aloe, is a species of flowering plant in the family Asphodelaceae. This woody aloe is indigenous to southern Africa. It is one of several ''Aloe'' species used to make bitter aloes, a purgative medicatio ...

'', are also cultivated or harvested from the wild for similar applications. The

APG IV system The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published ...

(2016) places the genus in the family

Asphodelaceae Asphodelaceae is a family of flowering plants in the order Asparagales. Such a family has been recognized by most taxonomists, but the circumscription has varied widely. In its current circumscription in the APG IV system, it includes about 4 ...

, subfamily

Asphodeloideae Asphodeloideae is a subfamily of the monocot family Asphodelaceae in the order Asparagales. It has previously been treated as a separate family, Asphodelaceae ''sensu stricto''. The family Asphodelaceae has now been proposed to be a nomen conserv ...

. Within the subfamily it may be placed in the tribe

Aloeae Aloeae is a tribe of succulent plants in the subfamily Asphodeloideae of the family Asphodelaceae, consisting of the aloes and their close relatives. The taxon may also be treated as the subfamily Alooideae by those botanists who retain the nar ...

.Stevens, P.F. (2001 onwards).
Asphodelaceae
. ''Angiosperm Phylogeny Website''. Retrieved 2016-06-09. In the past, it has been assigned to the family Aloaceae (now included in the Asphodeloidae) or to a broadly

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

family

Liliaceae The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair a ...

(the lily family). The plant ''

Agave americana ''Agave americana'', common names century plant, maguey, or American aloe, is a species of flowering plant in the family Asparagaceae, native to Mexico and the United States in Texas. It is cultivated worldwide as an ornamental plant, and has b ...

'', which is sometimes called "American aloe", belongs to the Asparagaceae, a different family. The genus is native to tropical and southern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Rive ...

, the Arabian Peninsula, and various islands in the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

(

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...

, Réunion, Comoros, etc.). A few species have also become naturalized in other regions (

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, Australia,

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

, Hawaiian Islands, etc.).

Taxonomy

The genus name ''Aloe'' is derived from the Arabic word ''alloeh'', meaning "bitter and shiny substance" or from

Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

''ahalim'', plural of ''ahal''.

Description

Most ''Aloe'' species have a rosette of large, thick, fleshy leaves. ''Aloe''

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s are tubular, frequently yellow, orange, pink, or red, and are borne, densely clustered and pendant, at the apex of simple or branched, leafless stems. Many species of ''Aloe'' appear to be stemless, with the rosette growing directly at ground level; other varieties may have a branched or unbranched stem from which the fleshy leaves spring. They vary in color from grey to bright-green and are sometimes striped or

mottle Mottle is a pattern of irregular marks, spots, streaks, blotches or patches of different shades or colours. It is commonly used to describe the surface of plants or the skin of animals. In plants, mottling usually consists of yellowish spots o ...

d. Some aloes native to South Africa are tree-like (arborescent).

Systematics

The

(2016) places the genus in the family

, subfamily

. In the past it has also been assigned to the families

and Aloeaceae, as well as the family Asphodelaceae sensu stricto, before this was merged into the Asphodelaceae

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

. The

circumscription Circumscription may refer to: *Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) *Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...

of the genus has varied widely. Many genera, such as ''Lomatophyllum'', have been brought into

synonymy A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

. Species at one time placed in ''Aloe'', such as ''

'', have been moved to other genera. Molecular phylogenetic studies, particularly from 2010 onwards, suggested that as then circumscribed, ''Aloe'' was not monophyletic and should be divided into more tightly defined genera. In 2014,

John Charles Manning John Charles Manning (born 1962) is a South African botanist based in the Compton Herbarium, South African National Biodiversity Institute, Kirstenbosch, South Africa. References External sources 20th-century South African botanists ...

and coworkers produced a phylogeny in which ''Aloe'' was divided into six genera: '' Aloidendron'', '' Kumara'', '' Aloiampelos'', ''Aloe'', '' Aristaloe'' and '' Gonialoe''.

Species

Over 600 species are accepted in the genus ''Aloe'', plus even more synonyms and unresolved species, subspecies, varieties, and hybrids. Some of the accepted species are: *'' Aloe aculeata'' Pole-Evans *''

Aloe africana ''Aloe africana'' (known as the Uitenhage Aloe) is an arborescent (tree-like) species of aloe plant, indigenous to the Eastern Cape Province, South Africa. Description The plant grows slowly and flowers when it is four to five years old. Fl ...

'' Mill. *''

Aloe albida ''Aloe albida'' is a dwarf species of succulent plant. Characteristics Its flowers are small, white and borne on a single inflorescence. Its flowering time is usually in early autumn (March–April in the Southern Hemisphere), although it may b ...

'' (Stapf) Reynolds *''

Aloe albiflora ''Aloe albiflora'' is a species of aloe indigenous to Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island cou ...

'' Guillaumin *''

Aloe arborescens ''Aloe arborescens'', the krantz aloe or candelabra aloe, is a species of flowering succulent perennial plant that belongs to the genus ''Aloe'', which it shares with the well known and studied ''Aloe vera''. The specific epithet ''arborescens'' ...

'' Mill. *'' Aloe arenicola'' Reynolds *''

Aloe argenticauda ''Aloe argenticauda'' is a species of plant in the genus ''Aloe''. It is endemic to Namibia. Its natural habitats are subtropical or tropical dry shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by ve ...

'' Merxm. & Giess *'' Aloe bakeri'' Scott-Elliot *'' Aloe ballii'' Reynolds *'' Aloe ballyi'' Reynolds *'' Aloe brevifolia'' Mill. *'' Aloe broomii'' Schönland *'' Aloe buettneri'' A.Berger *''

Aloe camperi ''Aloe camperi'' is a species of aloe indigenous to Africa, specifically the regions of Ethiopia and Eritrea. It grows in colonies, with orange flowers in early spring. External links Desert-tropicals.com profile
Aloe, camperi Flora of ...

'' Schweinf. *'' Aloe capitata'' Baker *'' Aloe comosa'' Marloth & A.Berger *''

Aloe cooperi Aloe cooperi, also known as Cooper's aloe and as ''iPutumane'' in Zulu language, Zulu, is a succulent species that is endemic to Southern Africa. It has significant cultural and economic value to the Zulu people of South Africa. Distribution T ...

'' Baker *''

Aloe corallina ''Aloe corallina'' is a species of plant in the genus ''Aloe''. It is native to Angola and Namibia. Its natural habitats are subtropical or tropical dry shrubland and rocky areas. It is threatened by habitat loss. References corallina ...

'' Verd. *'' Aloe dewinteri'' Giess ex Borman & Hardy *'' Aloe erinacea'' D.S.Hardy *''

Aloe excelsa ''Aloe excelsa'' (also known as the Zimbabwe Aloe) is an arborescent aloe indigenous to southern Africa. Description The Zimbabwe Aloe is a tall aloe, sometimes reaching tree dimensions of 5–6 metres, although 3 metres is a more common heig ...

'' A.Berger *''

'' Mill. *''

Aloe forbesii ''Aloe forbesii'' is a small stemless ''Aloe'' native to Socotra, Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Penins ...

'' Balf.f. *''

Aloe helenae ''Aloe helenae'' is a species of plant in the genus ''Aloe''. It is Endemism, endemic to Madagascar. References Sources

Aloe, helenae Critically endangered plants Endemic flora of Madagascar Taxonomy articles created by Polbot {{A ...

'' Danguy *'' Aloe hereroensis'' Engl. *''

Aloe inermis ''Aloe inermis'' is a small, stemless Aloe native to Yemen. See also *Succulent plant In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid cli ...

'' Forssk. *''

Aloe inyangensis ''Aloe inyangensis'' is a succulent aloe plant species, found only in the mountainous Eastern Highlands of Zimbabwe. It grows best in shady conditions but in some areas is also found in the open in heaths on mountain tops. There are two subspecie ...

'' Christian *''

Aloe jawiyon ''Aloe jawiyon'' is a species of plant in the genus Aloe. It is endemic to the island of Socotra, Yemen. Distribution and habitat It is one of three Aloe species that naturally occur on Socotra, the other two being ''Aloe perryi'' and ''Aloe squ ...

'' S.J.Christie, D.P.Hannon & Oakman ex A.G.Mill. *'' Aloe jucunda'' Reynolds *'' Aloe khamiesensis'' Pillans *'' Aloe kilifiensis'' Christian *'' Aloe maculata'' All. *'' Aloe marlothii'' A.Berger *'' Aloe mubendiensis'' Christian *'' Aloe namibensis'' Giess *'' Aloe nyeriensis'' Christian & I.Verd. *'' Aloe pearsonii'' Schönland *'' Aloe peglerae'' Schönland *''

Aloe perfoliata ''Aloe perfoliata'', the rubble aloe or mitre aloe, is a hardy creeping aloe, found in rocky, mountainous areas throughout the Western Cape, South Africa. Naming and classification ''Aloe perfoliata'' was formerly known as ''Aloe mitriformis''. ...

'' L. *''

Aloe perryi ''Aloe perryi'' (syn. ''Aloe forbesii'' Balf.f.; ''Aloe socotrina'') is a species of plant in the genus Aloe. It is endemic to the island of Socotra in Yemen, and is often known by its common name, Socotrine aloe.''Western Arabia and the Red Sea' ...

'' Baker *'' Aloe petricola'' Pole-Evans *'' Aloe polyphylla'' Pillans *''

Aloe rauhii ''Aloe rauhii'' (common name snowflake aloe) is a rare succulent and highly drought-resistant plant endemic to Madagascar. It is named after Professor Werner Rauh, who was a professor of Botany at the University of Heidelberg in Germany. Des ...

'' Reynolds *'' Aloe reynoldsii'' Letty *'' Aloe scobinifolia'' Reynolds & Bally *'' Aloe sinkatana'' Reynolds *''

Aloe squarrosa ''Aloe squarrosa'' is a species of flowering plant in the Asphodelaceae family. It is from the island of Socotra, Yemen. Distribution and habitat ''Aloe squarrosa'' is endemic to the island of Socotra, Yemen. It is one of three Aloe species t ...

'' Baker ex Balf.f. *'' Aloe striata'' Haw. *'' Aloe succotrina'' Lam. *''

Aloe suzannae ''Aloe suzannae'' is an endangered species of plant in the genus '' Aloe'', indigenous to the south of Madagascar. Description It is exceptional in its genus in having nocturnal fragrant flowers, presumably pollinated by nocturnal animals such ...

'' Decary *''

Aloe thraskii ''Aloe thraskii'', the dune aloe, is a South African plant in the genus ''Aloe''. Description The dune aloe is a tall, fast-growing, un-branched aloe, which develops a very large rosette. The long, pale, grey-green leaves are deeply grooved o ...

'' Baker *'' Aloe vera'' (L.) Burm.f. *'' Aloe viridiflora'' Reynolds *'' Aloe wildii'' (Reynolds) Reynolds In addition to the species and hybrids between species within the genus, several hybrids with other genera have been created in cultivation, such as between ''Aloe'' and ''

Gasteria ''Gasteria'' is a genus of succulent plants, native to South Africa (and the far south-west corner of Namibia). Naming The genus is named for its stomach-shaped flowers (''"gaster"'' is Latin for "stomach") that result from the swollen base on t ...

'' ( × ''Gasteraloe''), and between ''Aloe'' and '' Astroloba'' ('' ×Aloloba''). Aloe diversity

Uses

Aloe species are frequently cultivated as ornamental plants both in gardens and in pots. Many aloe species are highly decorative and are valued by collectors of succulents. ''Aloe vera'' is used both internally and externally on humans as

folk Folk or Folks may refer to: Sociology *Nation *People * Folklore ** Folk art ** Folk dance ** Folk hero ** Folk music *** Folk metal *** Folk punk *** Folk rock ** Folk religion * Folk taxonomy Arts, entertainment, and media * Folk Plus or Fo ...

alternative Alternative or alternate may refer to: Arts, entertainment and media * Alternative (''Kamen Rider''), a character in the Japanese TV series ''Kamen Rider Ryuki'' * ''The Alternative'' (film), a 1978 Australian television film * ''The Alternative ...

medicine. The ''Aloe'' species is known for its medicinal and cosmetic properties. Around 75% of ''Aloe'' species are used locally for medicinal uses. The plants can also be made into types of special soaps or used in other skin care products (see

natural skin care Natural skin care uses topical creams and lotions made of ingredients available in nature. Much of the recent literature reviews plant-derived ingredients, which may include herbs, roots, flowers and essential oils, but natural substances in ski ...

). Numerous cultivars with mixed or uncertain parentage are grown. Of these, ''Aloe'' ‘Lizard Lips’ has gained the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nor ...

’s Award of Garden Merit. ''Aloe variegata'' has been planted on graves in the superstitious belief that this ensures eternal life.

Historical uses

Historical use of various aloe species is well documented. Documentation of the clinical effectiveness is available, although relatively limited. Of the 500+ species, only a few were used traditionally as herbal medicines, ''Aloe vera'' again being the most commonly used species. Also included are ''A. perryi'' and ''A. ferox''. The Ancient Greeks and Romans used ''Aloe vera'' to treat wounds. In the Middle Ages, the yellowish liquid found inside the leaves was favored as a

purgative Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...

. Unprocessed aloe that contains

aloin Aloin, also known as barbaloin, is a bitter, yellow-brown colored compound noted in the exudate of at least 68 ''Aloe'' species at levels from 0.1 to 6.6% of leaf dry weight (making between 3% and 35% of the total exudate), and in another 17 spec ...

is generally used as a laxative, whereas processed juice does not usually contain significant aloin. Some species, particularly ''Aloe vera'', are used in alternative medicine and first aid. Both the translucent inner pulp and the resinous yellow aloin from wounding the aloe plant are used externally for skin discomforts. As an herbal medicine, ''Aloe vera'' juice is commonly used internally for digestive discomfort. According to

Cancer Research UK Cancer Research UK (CRUK) is the world's largest independent cancer research organization. It is registered as a charity in the United Kingdom and Isle of Man, and was formed on 4 February 2002 by the merger of The Cancer Research Campaign and t ...

, a potentially deadly product called T-UP is made of concentrated aloe, and promoted as a cancer cure. They say "there is currently no evidence that aloe products can help to prevent or treat cancer in humans".

Aloin in OTC laxative products

On May 9, 2002, the US Food and Drug Administration issued a final rule banning the use of aloin, the yellow sap of the aloe plant, for use as a laxative ingredient in

over-the-counter drug Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid prescr ...

products. Most aloe juices today do not contain significant aloin.

Chemical properties

According to W. A. Shenstone, two classes of aloins are recognized: (1) nataloins, which yield picric and oxalic acids with

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

, and do not give a red coloration with nitric acid; and (2) barbaloins, which yield aloetic acid (C₇H₂N₃O₅), chrysammic acid (C₇H₂N₂O₆), picric and oxalic acids with nitric acid, being reddened by the acid. This second group may be divided into a-barbaloins, obtained from Barbados ''Aloe'', and reddened in the cold, and b-barbaloins, obtained from ''Aloe Socotrina'' and Zanzibar ''Aloe'', reddened by ordinary nitric acid only when warmed or by fuming acid in the cold. Nataloin (2C₁₇H₁₃O₇·H₂O) forms bright-yellow scales, barbaloin (C₁₇H₁₈O₇) Prism (geometry), prismatic crystals. ''Aloe'' species are used in essential oils as a safety measure to dilute the solution before they are applied to the skin.

Flavoring

''Aloe perryi'', ''A. barbadensis'', ''A. ferox'', and hybrids of this species with ''A. africana'' and ''A. spicata'' are listed as natural flavoring substances in the US government ''Electronic Code of Federal Regulations''. ''Aloe socotrina'' is said to be used in yellow Chartreuse (liqueur), Chartreuse.John Tellman (1900
''The Practical Hotel Steward''
The Hotel Monthly, Chicago

Heraldic occurrence

''Aloe rubrolutea'' occurs as a charge in heraldry, for example in the Civic Heraldry of Namibia.

Gallery

File:Aloe vossii - plant (aka).jpg, ''Aloe vossii'' File:Aloe rubroviolacea2.jpg, ''Aloe rubroviolacea, A. rubroviolacea'' File:Aloe africana 1.jpg, ''

'' (Uitenhage aloe) File:Gardenology-IMG 5394 hunt10mar.jpg, '' Aloe marlothii'' (flat-flowered aloe) File:Aloe pluridens (3).jpg, ''Aloe pluridens'' (French aloe) File:Aloe excelsa at Mount Coot-tha.JPG, ''

'' (Zimbabwe aloe) File:Aloe rupestris, vroeë bloeiwyse, Pretoria.jpg, ''Aloe rupestris'' (bottlebrush aloe) File:Aloe speciosa - tilt head aloe.jpg, ''Aloe hexapetala'' (tilt-headed aloe) File:Blooming aloes wide view alternate, with bright sun behind.jpg, Blooming ''

'' File:Aloe cooperi in flower IMG 1702e.JPG, ''Aloe cooperi'' (''Aloe plicatilis'' in background on the right) File:Aloe hereroensis Auob C15.JPG, '' Aloe hereroensis'' File:Aloe peglerae01.jpg, '' Aloe peglerae'' File:Aloe saponaria 1.jpg, '' Aloe maculata'' - prev. ''A. saponaria'' (soap aloe) File:Aloe reitzii flowers.jpg, ''Aloe reitzii''

References

External links

{{Authority control Aloe, Plants used in Ayurveda Asphodelaceae genera Laxatives Cosmetics chemicals Succulent plants