Usnic acid
Encyclopedia
Usnic acid is a naturally occurring dibenzofuran
Dibenzofuran
Dibenzofuran, is a heterocyclic organic compound with the chemical structure shown at right. It is an aromatic compound that has two benzene rings fused to one furan ring in the middle. All of the numbered carbon atoms have a hydrogen atom bonded to each of them...

 derivative found in several lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

 species. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933-1937 by Curd and Robertson. Usnic acid was identified in many genera of lichens including Usnea
Usnea
Usnea is the generic and scientific name for several species of lichen in the family Parmeliaceae, that generally grow hanging from tree branches, resembling grey or greenish hair. It is sometimes referred to commonly as Old Man's Beard, Beard Lichen, or Treemoss...

, Cladonia
Cladonia
Cladonia is a genus of moss-like lichens in the family Cladoniaceae. They are the primary food source for reindeer and caribou. Cladonia species are of economic importance to reindeer-herders, such as the Sami in Scandinavia or the Nenets in Russia. Antibiotic compounds are extracted from some...

, Lecanora
Lecanora
Lecanora is a genus of lichen belonging to the suborder Lecanorineae.-Historical Mention:Lecanora Tartarea was probably the Viking dye-moss from which the English word litmus derives because it is commonly found in Norway and Sweden.-External links:*...

, Ramalina
Ramalina
Ramalina is a genus of lichens belonging to the suborder Lecanorineae. The genus has a widespread distribution and contains over 240 species....

, Evernia
Evernia
Evernia is a bushy lichen in the family Parmeliaceae. Two species, Oakmoss Evernia prunastri, and Treemoss Evernia furfuracea are used as a fixative agent in cologne within the perfume industry. It is green on top and white on bottom, and divides evenly into "forks." Not to be confused with...

, Parmelia
Parmelia (lichen)
Parmelia is a large genus of lichenized fungus with a global distribution, extending from the Arctic to the Antarctic continent but concentrated in temperate regions. 125 species have been recorded on the Indian sub-continent...

and Alectoria. Although it is generally believed that usnic acid is exclusively restricted to lichens, in a few unconfirmed isolated cases the compound was found in kombucha
Kombucha
Kombucha is an effervescent tea-based beverage that is often drunk for its anecdotal health benefits or medicinal purposes. Kombucha is available commercially and can be made at home by fermenting tea using a visible, solid mass of yeast and bacteria which forms the kombucha culture, often referred...

 tea and non-lichenized ascomycetes.

At normal conditions, usnic acid is a bitter, yellow, solid substance. It is known to occur in nature in both the d- and l-forms as well as a racemic mixture.

Biological role in lichens

Usnic acid is a secondary metabolite in lichens whose role has not been completely elucidated. It is believed that usnic acid protects the lichen from adverse effects of sunlight exposure and deters grazing animals with its bitter taste.

Uses and properties

Lichen extracts containing usnic acid have been utilized in medicine, perfumery, cosmetics, and ecology.

Usnic acid possess a wide range of interesting biological properties. It is a potent antibiotic effective against gram positive bacteria, including Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...

, Staphylococcus
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....

, Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

, and Pneumococcus, as well as some pathogenic fungi. It also exhibits antiviral, antiprotozoal, antimitotic, anti-inflammatory and analgesic activity. Other characteristics, like ultraviolet absorption, preserving properties, antigrowth, antiherbivore and anti-insect properties, have also been demonstrated.

Usnic acid has been included as an ingredient in creams, powders, toothpastes, mouthwash, deodorants, hair shampoos and sunscreen products. In some of these preparations, usnic acid is employed as an active principle, in others as a preservative.

Usnic acid and its salt form, sodium usniate, have been marketed in the US as an ingredient in food supplements for use in weight reduction, although unsupported by solid scientific proof. These supplements, if taken according to label instructions, can supply daily oral doses of 10–1350 mg for adults. Daily oral intake of 300–1350 mg over a period of weeks has led to severe hepatotoxicity in a number of persons.
Usnea was one ingredient in a product called Lipokinetix, promoted to induce weight loss via increase in metabolic rate. Lipokinetix has been the topic of an FDA warning in the USA, due to potential hepatotoxicity, although it is unclear yet if any toxicity would be attributable to the Usnea. Lipokinetix also contained PPA, caffeine, yohimbine and diiodothyronine. There is reason to believe that usnic acid, in high concentrations, could possess some toxicity. The National Toxicology Program is currently evaluating the issue.

Pharmacolgy

Usnic acid has been found to have adrenergic activity in both frog and earthworm nerve junction models in preliminary research.

External links

  • http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=search&db=pcsubstance&term=usnic%20acid
  • http://bioweb.ucr.edu/ChemMine/view.php?TYPE=1&i_id=996789
  • http://ntp.niehs.nih.gov/index.cfm?objectid=E87D09E6-BDB5-82F8-FF11A36F2EEA025F
  • http://query.nytimes.com/gst/fullpage.html?res=9802E2DD163FF937A35750C0A9659C8B63
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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