| Usnic acid | |
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2,6-Diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bh) |
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Other names
usneine, usninic acid, usniacin |
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| Identifiers | |
| CAS number | [1] 125-46-2[1] |
| PubChem | 5646 |
| ChemSpider | 5444 |
| ChEMBL | CHEMBL242022 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C18H16O7 |
| Molar mass | 344.315 g/mol |
| Melting point |
204 °C |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species. It was first isolated by German scientist W. Knop in 1844[2] and first synthesized between 1933-1937 by Curd and Robertson.[3] Usnic acid was identified in many genera of lichens including Usnea, Cladonia, Lecanora, Ramalina, Evernia, Parmelia 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 tea and non-lichenized ascomycetes.
At normal conditions, usnic acid is a bitter, yellow, solid substance.[1] It is known to occur in nature in both the d- and l-forms as well as a racemic mixture.
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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.
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, Staphylococcus, Streptococcus, 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.[4][5] 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,[6] 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.
Usnic acid has been found to have adrenergic activity in both frog and earthworm nerve junction models in preliminary research.[7]