Aloin
Encyclopedia
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 toal exudate) (Groom & Reynolds, 1987), and in another 17 species at indeterminate levels [Reynolds, 1995b]. It is used as a stimulant-laxative
, treating constipation
by inducing bowel movements. The compound is present in what is commonly referred to as the aloe latex
that exudes from cells adjacent to the vascular bundles, found under the rind of the leaf and in between it and the gel. When dried, it has been used as a bittering agent in commerce (alcoholic beverages) [21 CFR 172.510. Scientific names given include Aloe perryi, A. barbadensis (= A. vera), A. ferox, and hybrids of A. ferox with A. africana and A. spicata.]. Aloe is listed in federal regulations as a natural substance that may be “safely used in food” when used “in the minimum quantity required to produce their intended physical or technical effect and in accordance with all the principles of good manufacturing practice.” This food application is generally limited to use in quite small quantities as a flavoring in alcoholic beverages and may usually be identified only as a “natural flavor.”
In May 2002, the U.S. Food and Drug Administration (FDA) issued a ruling that aloe laxatives are no longer generally recognized as safe
(GRAS) and effective, meaning that aloin-containing products are no longer available in over-the-counter drug
products in the United States, because they may be carcinogen
ic and more data is needed to establish otherwise. Aloe vera leaf latex is a concentrate of an herb or other botanical, and so meets the statutory description of an ingredient that may be used in dietary supplements.
s, termed aloin A (also called barbaloin) and aloin B (or isobarbaloin), which have similar chemical properties. Aloin is an anthraquinone glycoside
, meaning that its anthraquinone skeleton has been modified by the addition of a sugar molecule. Anthraquinone
s are a common family of naturally occurring yellow, orange, and red pigments of which many have cathartic properties, attributes shared by aloin. Aloin is related to aloe emodin
, which lacks a sugar group but shares aloin's biological properties.
Aloin is usually prepared by extraction from aloe latex (the term "Cape aloe" also refers to the dried latex of the leaves of several species of the Aloe genus, especially A. ferox [Blumenthal, 1998]), the bitter yellow exudate that seeps out from just underneath the skin of aloe leaves. The latex is then dried and powdered to make the final product, often made into tablets or a beverage, though aloin does not have good stability in aqueous solutions. Products derived from the gel of the aloe plant do not contain appreciable amounts of aloin, and have not been proven effective for any disease or condition when taken orally.
in the colon, which induces bowel movements. Aloin also prevents the colon from re-absorbing water from the gastrointestinal tract, which leads to softer stools. This effect is caused by aloin's opening of chloride channels of the colonic membrane. In higher doses, these effects may lead to electrolyte imbalance, diarrhea, and abdominal pain, which are common side-effects of the drug. Because aloin can potentially cause uterine contractions, pregnant women should avoid ingesting aloe products.
In a study on consumption of aloe in rats and tilapia
(with no separation of gel from aloin), significant negative health effects were found, including normocytic normochromic anaemia (low red blood cell count, but normal cells), hypoproteinaemia, and high AST
levels. As many studies involving aloe gel (without aloin) have not observed these negative effects, it is possible that the negative effects could in large part be due to aloin.
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...
, treating constipation
Constipation
Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...
by inducing bowel movements. The compound is present in what is commonly referred to as the aloe latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
that exudes from cells adjacent to the vascular bundles, found under the rind of the leaf and in between it and the gel. When dried, it has been used as a bittering agent in commerce (alcoholic beverages) [21 CFR 172.510. Scientific names given include Aloe perryi, A. barbadensis (= A. vera), A. ferox, and hybrids of A. ferox with A. africana and A. spicata.]. Aloe is listed in federal regulations as a natural substance that may be “safely used in food” when used “in the minimum quantity required to produce their intended physical or technical effect and in accordance with all the principles of good manufacturing practice.” This food application is generally limited to use in quite small quantities as a flavoring in alcoholic beverages and may usually be identified only as a “natural flavor.”
In May 2002, the U.S. Food and Drug Administration (FDA) issued a ruling that aloe laxatives are no longer generally recognized as safe
Generally recognized as safe
Generally recognized as safe is an American Food and Drug Administration designation that a chemical or substance added to food is considered safe by experts, and so is exempted from the usual Federal Food, Drug, and Cosmetic Act food additive tolerance requirements.-History:On January 1, 1958,...
(GRAS) and effective, meaning that aloin-containing products are no longer available 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 in the United States, because they may be carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic and more data is needed to establish otherwise. Aloe vera leaf latex is a concentrate of an herb or other botanical, and so meets the statutory description of an ingredient that may be used in dietary supplements.
Structure and preparation
Aloin extracted from natural sources is a mixture of two diastereomerDiastereomer
Diastereomers are stereoisomers that are not enantiomers.Diastereomerism occurs when two or more stereoisomers of a compound have different configurations at one or more of the equivalent stereocenters and are not mirror images of each other.When two diastereoisomers differ from each other at...
s, termed aloin A (also called barbaloin) and aloin B (or isobarbaloin), which have similar chemical properties. Aloin is an anthraquinone glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
, meaning that its anthraquinone skeleton has been modified by the addition of a sugar molecule. Anthraquinone
Anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative...
s are a common family of naturally occurring yellow, orange, and red pigments of which many have cathartic properties, attributes shared by aloin. Aloin is related to aloe emodin
Aloe emodin
Aloe emodin is a carcinogenic anthraquinone present in aloe latex, an exudate from the aloe plant. It has a strong stimulant-laxative action....
, which lacks a sugar group but shares aloin's biological properties.
Aloin is usually prepared by extraction from aloe latex (the term "Cape aloe" also refers to the dried latex of the leaves of several species of the Aloe genus, especially A. ferox [Blumenthal, 1998]), the bitter yellow exudate that seeps out from just underneath the skin of aloe leaves. The latex is then dried and powdered to make the final product, often made into tablets or a beverage, though aloin does not have good stability in aqueous solutions. Products derived from the gel of the aloe plant do not contain appreciable amounts of aloin, and have not been proven effective for any disease or condition when taken orally.
Effects
Once ingested, aloin increases peristaltic contractionsPeristalsis
Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar...
in the colon, which induces bowel movements. Aloin also prevents the colon from re-absorbing water from the gastrointestinal tract, which leads to softer stools. This effect is caused by aloin's opening of chloride channels of the colonic membrane. In higher doses, these effects may lead to electrolyte imbalance, diarrhea, and abdominal pain, which are common side-effects of the drug. Because aloin can potentially cause uterine contractions, pregnant women should avoid ingesting aloe products.
In a study on consumption of aloe in rats and tilapia
Tilapia
Tilapia , is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats, including shallow streams, ponds, rivers and lakes. Historically, they have been of major importance in artisan fishing in Africa and the...
(with no separation of gel from aloin), significant negative health effects were found, including normocytic normochromic anaemia (low red blood cell count, but normal cells), hypoproteinaemia, and high AST
Alanine transaminase
Alanine transaminase or ALT is a transaminase enzyme . It is also called serum glutamic pyruvic transaminase or alanine aminotransferase ....
levels. As many studies involving aloe gel (without aloin) have not observed these negative effects, it is possible that the negative effects could in large part be due to aloin.