Aloe
Encyclopedia
Aloe icon, also Aloë, is a genus
containing about 500 species
of flowering
succulent
plant
s. The most common and well known of these is Aloe vera
, or "true aloe".
The genus is native to Africa
, and is common in South Africa
's Cape Province
, the mountains of tropical Africa, and neighboring areas such as Madagascar
, the Arabian peninsula
, and the islands of Africa.
The APG III system
(2009) places the genus in the family Xanthorrhoeaceae
, subfamily Asphodeloideae. In the past it has also been assigned to families Aloaceae and Liliaceae
or lily family. Members of the closely allied genera Gasteria
, Haworthia
and Kniphofia
, which have a similar mode of growth, are also popularly known as aloes. The plant Agave americana, which is sometimes called "American aloe", belongs to Asparagaceae
, a different family.
Most Aloe species have a rosette
of large, thick, fleshy leaves
. The leaves are often lance-shaped with a sharp apex and a spiny margin. Aloe flower
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
d. Some Aloes native to South Africa are arborescent.
is used both internally and externally on humans, and is claimed to have some medicinal effects, which have been supported by scientific and medical research. The gel in the leaves can be made into a smooth type of cream that can heal burns such as sunburn. They can also be made into types of special soaps.
s is well documented. Documentation of the clinical effectiveness is available, although relatively limited.
Of the 500+ species of Aloe, only a few were used traditionally as a herbal medicine, aloe vera
again being the most commonly used version of aloe in herbal medicine. Also included are Aloe perryi (found in northeastern Africa
) and Aloe ferox (found in South Africa
). The Greeks
and Romans
used aloe vera to treat wound
s. In the Middle Ages
, the yellowish liquid found inside the leaves
was favored as a purgative. Unprocessed aloe that contains aloin
is generally used as a laxative, whereas processed aloe vera juice does not usually contain significant aloin.
Some species, particularly Aloe vera
are used in alternative medicine
and in the home first aid
s. Both the translucent inner pulp and the resinous yellow aloin
from wounding the Aloe plant are used externally to relieve skin discomforts. As an herbal medicine, aloe vera juice is commonly used internally to relieve digestive discomfort. Some modern research suggests Aloe vera can significantly slow wound healing compared to normal protocols of treatment. Other reviews of randomised and controlled clinical trials have provided no evidence that Aloe vera has a strong medicinal effect.
Today, aloe vera is used both internally and externally on humans. The gel found in the leaves is used for soothing minor burns, wound
s, and various skin conditions like eczema
and ringworm. The extracted aloe vera juice aloe vera plant is used internally to treat a variety of digestive conditions. The use of this herbal medicine was popularized in the 1950s in many Western countries
. The gel's effect is nearly immediate; it also applies a layer over wound
s that is said to reduce the chance of any infection
. Despite its popularity, aloe is an allergen and should always be tested before use.
There have been relatively few studies about possible benefits of Aloe gel taken internally. Components of Aloe may inhibit tumor growth. There have been some studies in animal models which indicate that extracts of Aloe have a significant anti-hyperglycemic effect, and may be useful in treating Type II diabetes. These studies have not been confirmed in humans.
On May 9, 2002, the U.S. 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
products. Most aloe juices today do not contain significant aloin.
According to W. A. Shenstone, two classes of aloin
s are to be recognized: (1) nataloins, which yield picric
and oxalic acid
s with nitric acid
, 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 Socotrine 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
atic crystals. Aloe species also contain a trace of volatile oil, to which its odour is due.
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Aloe rubrolutea occurs as a charge in heraldry
, such as in the Civic Heraldry of Namibia.
An Aloe tree appeared on stamps issued in 1919 by Batum, a semi-autonomous region of Georgia
in the South Caucasus
region.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
containing about 500 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of flowering
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
succulent
Succulent plant
Succulent plants, also known as succulents or fat plants, are water-retaining plants adapted to arid climates or soil conditions. Succulent plants store water in their leaves, stems, and also in roots...
plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s. The most common and well known of these is Aloe vera
Aloe vera
Aloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
, or "true aloe".
The genus is native to Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, and is common in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
's Cape Province
Cape Province
The Province of the Cape of Good Hope was a province in the Union of South Africa and subsequently the Republic of South Africa...
, the mountains of tropical Africa, and neighboring areas such as Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, the Arabian peninsula
Arabian Peninsula
The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...
, and the islands of Africa.
The APG III system
APG III system
The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy...
(2009) places the genus in the family Xanthorrhoeaceae
Xanthorrhoeaceae
Xanthorrhoeaceae is the botanical name of a family of flowering plants in the order Asparagales. Such a family has been recognized by most taxonomists, but the circumscription of the family has varied wildly....
, subfamily Asphodeloideae. In the past it has also been assigned to families Aloaceae and Liliaceae
Liliaceae
The Liliaceae, or the lily family, is a family of monocotyledons in the order Liliales. Plants in this family have linear leaves, mostly with parallel veins but with several having net venation , and flower arranged in threes. Several have bulbs, while others have rhizomes...
or lily family. Members of the closely allied genera Gasteria
Gasteria
Gasteria is a genus of succulent plants native to South Africa. Closely related genera include Aloe and Haworthia. The genus is named for its stomach-shaped flowers and is part of the family Xanthorrhoeaceae, subfamily Asphodeloideae...
, Haworthia
Haworthia
Haworthia is a genus of flowering plants within the family Xanthorrhoeaceae, subfamily Asphodeloideae.. They are small solitary or clump-forming and endemic to South Africa. Some species have firm, tough leaves, usually dark green in color, whereas other are soft and semi-translucent. Their...
and Kniphofia
Kniphofia
Kniphofia , also called Tritoma, Red hot poker, Torch lily or Poker plant, is a genus of plants in the family Xanthorrhoeaceae, subfamily Asphodeloideae, that includes 70 or more species native to Africa...
, which have a similar mode of growth, are also popularly known as aloes. The plant Agave americana, which is sometimes called "American aloe", belongs to Asparagaceae
Asparagaceae
Asparagaceae is the botanical name of a family of flowering plants, placed in the order Asparagales of the monocots.In earlier classification systems, the species involved were often treated as belonging to the family Liliaceae...
, a different family.
Most Aloe species have a rosette
Rosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
of large, thick, fleshy leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
. The leaves are often lance-shaped with a sharp apex and a spiny margin. Aloe flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
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
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
from which the fleshy leaves spring. They vary in color from grey to bright-green and are sometimes striped or mottle
Mottle
Mottle or mottling is the appearance of uneven spots. It is commonly used to describe plants or the skin of animals. In plants, mottling usually consists of yellowish spots on plants, and is usually a sign of disease or malnutrition...
d. Some Aloes native to South Africa are arborescent.
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 veraAloe vera
Aloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
is used both internally and externally on humans, and is claimed to have some medicinal effects, which have been supported by scientific and medical research. The gel in the leaves can be made into a smooth type of cream that can heal burns such as sunburn. They can also be made into types of special soaps.
Historical uses
Historical use of various Aloe species by humanHuman
Humans are the only living species in the Homo genus...
s is well documented. Documentation of the clinical effectiveness is available, although relatively limited.
Of the 500+ species of Aloe, only a few were used traditionally as a herbal medicine, aloe vera
Aloe vera
Aloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
again being the most commonly used version of aloe in herbal medicine. Also included are Aloe perryi (found in northeastern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
) and Aloe ferox (found in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
). The Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
and Romans
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
used aloe vera to treat wound
Wound
A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...
s. In the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
, the yellowish liquid found inside the leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
was favored as a purgative. Unprocessed aloe that contains aloin
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 , and in another 17 species at indeterminate levels [Reynolds, 1995b]...
is generally used as a laxative, whereas processed aloe vera juice does not usually contain significant aloin.
Some species, particularly Aloe vera
Aloe vera
Aloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
are used in alternative medicine
Alternative medicine
Alternative medicine is any healing practice, "that does not fall within the realm of conventional medicine." It is based on historical or cultural traditions, rather than on scientific evidence....
and in the home first aid
First aid
First aid is the provision of initial care for an illness or injury. It is usually performed by non-expert, but trained personnel to a sick or injured person until definitive medical treatment can be accessed. Certain self-limiting illnesses or minor injuries may not require further medical care...
s. Both the translucent inner pulp and the resinous yellow aloin
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 , and in another 17 species at indeterminate levels [Reynolds, 1995b]...
from wounding the Aloe plant are used externally to relieve skin discomforts. As an herbal medicine, aloe vera juice is commonly used internally to relieve digestive discomfort. Some modern research suggests Aloe vera can significantly slow wound healing compared to normal protocols of treatment. Other reviews of randomised and controlled clinical trials have provided no evidence that Aloe vera has a strong medicinal effect.
Today, aloe vera is used both internally and externally on humans. The gel found in the leaves is used for soothing minor burns, wound
Wound
A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...
s, and various skin conditions like eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
and ringworm. The extracted aloe vera juice aloe vera plant is used internally to treat a variety of digestive conditions. The use of this herbal medicine was popularized in the 1950s in many Western countries
Country
A country is a region legally identified as a distinct entity in political geography. A country may be an independent sovereign state or one that is occupied by another state, as a non-sovereign or formerly sovereign political division, or a geographic region associated with a previously...
. The gel's effect is nearly immediate; it also applies a layer over wound
Wound
A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...
s that is said to reduce the chance of any infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
. Despite its popularity, aloe is an allergen and should always be tested before use.
There have been relatively few studies about possible benefits of Aloe gel taken internally. Components of Aloe may inhibit tumor growth. There have been some studies in animal models which indicate that extracts of Aloe have a significant anti-hyperglycemic effect, and may be useful in treating Type II diabetes. These studies have not been confirmed in humans.
Aloin in OTC laxative products
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 , and in another 17 species at indeterminate levels [Reynolds, 1995b]...
, the yellow sap of the aloe plant for use as a laxative ingredient in over-the-counter drug
Over-the-counter drug
Over-the-counter drugs are medicines that may be sold directly to a consumer without a prescription from a healthcare professional, as compared to prescription drugs, which may be sold only to consumers possessing a valid prescription...
products. Most aloe juices today do not contain significant aloin.
Chemical properties
According to W. A. Shenstone, two classes of aloin
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 , and in another 17 species at indeterminate levels [Reynolds, 1995b]...
s are to be recognized: (1) nataloins, which yield picric
Picric acid
Picric acid is the chemical compound formally called 2,4,6-trinitrophenol . This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive...
and oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...
s with nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, 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 Socotrine 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
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
atic crystals. Aloe species also contain a trace of volatile oil, to which its odour is due.
Popular culture
Heraldry
Heraldry is the profession, study, or art of creating, granting, and blazoning arms and ruling on questions of rank or protocol, as exercised by an officer of arms. Heraldry comes from Anglo-Norman herald, from the Germanic compound harja-waldaz, "army commander"...
, such as in the Civic Heraldry of Namibia.
Species
There are around 400 species in the genus Aloe. For a full list, see List of species of genus Aloe. Species include:- Aloe veraAloe veraAloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
- used in healthcare & health products - Aloe arborescensAloe arborescensAloe arborescens, commonly known as the Krantz Aloe, belongs to the Aloe genus, which it shares with the well known and studied Aloe vera plant. This species is also relatively popular among gardeners and has recently been studied for possible medical uses...
- used in healthcare - Aloe aristataAloe aristataAloe aristata, also known as Torch Plant and Lace Aloe, is a species of aloe indigenous to South Africa and surrounding countries. It is stemless, sawtoothed and succulent. Its nectar-rich flowers tend to attract birds, bees, and wasps easily....
- Torch Plant, Lace Aloe - Aloe dichotomaAloe dichotomaAloe dichotoma, also known as Quiver tree or Kokerboom, is a species of aloe indigenous to Southern Africa, specifically in the Northern Cape region, and Namibia....
- quiver tree or kokerboom - Aloe nyeriensis
- Aloe variegataAloe variegataAloe variegata, also known as Tiger Aloe and Partridge-breasted Aloe, is a species of aloe indigenous to South Africa and Namibia.-Description:...
- Partridge-breasted Aloe, Tiger Aloe - Aloe barbadensis - Barbados Aloe, Common Aloe, Yellow Aloe, Medicinal Aloe. This is an older name for Aloe vera.
- Aloe wildiiAloe wildii250px|thumb|rightAloe wildii is a grasslike aloe.It is native to a small area in south-east Africa and, like other succulent plants, it is resistant to drought...
Trivia
Georgia (country)
Georgia is a sovereign state in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded to the west by the Black Sea, to the north by Russia, to the southwest by Turkey, to the south by Armenia, and to the southeast by Azerbaijan. The capital of...
in the South Caucasus
South Caucasus
The South Caucasus is a geopolitical region located on the border of Eastern Europe and Southwest Asia also referred to as Transcaucasia, or The Trans-Caucasus...
region.