Aloin
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Aloin, also known as barbaloin, is a bitter, yellow-brown colored compound noted in the exudate of at least 68 ''
Aloe ''Aloe'' (; also written ''Aloƫ'') is a genus containing over 650 species of flowering plant, flowering succulent plant, succulent plants.WFO (2022): Aloe L. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-4000001341. Acc ...
'' 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 species at indeterminate levels eynolds, 1995b It is used as a stimulant-
laxative 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 ...
, treating
constipation Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The Human feces, stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the ...
by inducing
bowel The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. T ...
movements. The compound is present in what is commonly referred to as the aloe
latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latices are found in nature, but synthetic latices are common as well. In nature, latex is found as a wikt:milky, milky fluid, which is present in 10% of all floweri ...
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 A bittering agent is a flavoring agent added to a food or beverage to impart a bitter taste, possibly in addition to other effects. While many substances are bitter to a greater or lesser degree, a few substances are used specifically for their bi ...
in commerce (alcoholic beverages) 1 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 The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(FDA) issued a ruling that aloe laxatives are no longer
generally recognized as safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...
(GRAS) and effective, meaning that aloin-containing products are no longer available 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 pres ...
products in the United States, because they may be
carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...
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
diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...
s, termed aloin A (also called barbaloin) and aloin B (or isobarbaloin), which have similar chemical properties. Aloin is an anthraquinone
glycosyl In organic chemistry, a glycosyl group is a univalent free radical or substituent structure obtained by removing the hydroxyl () group from the hemiacetal () group found in the cyclic form of a monosaccharide and, by extension, of a lower ol ...
, meaning that its anthraquinone skeleton has been modified by the addition of a sugar molecule. Anthraquinones 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 genus ''Aloe'', especially ''A. ferox'' lumenthal, 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 contractions 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 containing aloin in more than trace amounts. 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 Anemia (also spelt anaemia in British English) is a blood disorder in which the blood has a reduced ability to carry oxygen. This can be due to a lower than normal number of red blood cells, a reduction in the amount of hemoglobin availab ...
(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.


Legal status

Plant-derived remedies containing aloin and other anthraquinones have been used as traditional medicines since antiquity, but harsh side effects make these substances generally unsuitable for household or daily use. In 2002, the US FDA mandated that manufacturers reformulate or stop manufacturing over-the-counter products containing aloe because the agency did not receive necessary safety data. The substance is still allowed in dietary supplements 1 U.S.C. 321 (ff)(1)and is allowed for use in foods (primarily alcoholic beverages).


References


External links


Aloin MSDS
{{Authority control Anthraquinone glucosides Bitter compounds Plant toxins