“Usnic acid”的意思、由来-开放百科全书

At normal conditions, usnic acid is a bitter, yellow, solid substance.^[5] It is known to occur in nature in both the d- and l-forms as well as a racemic mixture. Salts of usnic acid are called usnates (e.g. copper usnate).

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 used in medicine, perfumery, cosmetics, and ecology.

Usnic acid possesses a wide range of biological properties. It is a potent antibiotic effective against Gram-positive bacteria, including Staphylococcus, Streptococcus, and Pneumococcus, other bacteria such as Mycobacterium tuberculosis, and some pathogenic fungi.{{medcn|date=July 2018}} It also exhibits antiviral, antiprotozoal, antimitotic, anti-inflammatory and analgesic activity.{{medcn|date=July 2018}} 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 this effect is unsupported by scientific evidence. These supplements, if taken according to label instructions, can supply daily oral doses of 10–1350 mg for adults.

Safety

Usnic acid and its salts are idiosyncratically associated with severe hepatotoxicity and liver failure.^[6] Daily oral intake of 300–1350 mg over a period of weeks has led to severe hepatotoxicity in a number of persons.^[7]^[8]

Sodium usniate was one ingredient in a product called "Lipokinetix", that was claimed to induce weight loss via an increase in metabolic rate. Lipokinetix has been the topic of an FDA warning in the USA,^[9] due to potential hepatotoxicity, although it is unclear yet if any toxicity would be attributable to the aforementioned salt. Lipokinetix also contained norephedrine (PPA), caffeine, yohimbine and 3,5-diiodothyronine.

Pharmacology

Usnic acid has been found to have adrenergic activity in both frog and earthworm nerve junction models in preliminary research.^[10]

Analytics

It is possible to determine the content of usnic acid in lichen extract using reversed-polarity capillary zone electrophoretic analysis.^[11]

References

1. ^{{cite journal | last1 = Knop | first1 = W | year = 1844 | title = Chemisch-physiologische Untersuchung uber die Flechten | url = | journal = Justus Lieb. Ann. Chem. | volume = 49 | issue = 2| pages = 103–124 | doi=10.1002/jlac.18440490202}}
2. ^{{cite journal | last1 = Robertson | first1 = A. | last2 = Curd | first2 = F. H. | year = 1933 | title = 277. Usnic acid. Part III. Usnetol, usnetic acid, and pyrousnic acid| url = | journal = J. Chem. Soc. | volume = | issue = | page = 1173 | doi = 10.1039/jr9330001173 }}
3. ^{{cite journal|last1=Cocchietto|first1=Moreno|last2=Skert|first2=Nicola|last3=Nimis|first3=Pier|last4=Sava|first4=Gianni|title=A review on usnic acid, an interesting natural compound|journal=Naturwissenschaften|volume=89|issue=4|year=2002|pages=137–146|issn=0028-1042|doi=10.1007/s00114-002-0305-3}}
4. ^{{cite journal|last1=Blanc|first1=Philippe J.|title=Characterization of the tea fungus metabolites|journal=Biotechnology Letters|volume=18|issue=2|year=1996|pages=139–142|issn=0141-5492|doi=10.1007/BF00128667}}
5. ^¹{{cite book| author1 =Michael Ash| author2 =Irene Ash| title =Handbook of preservatives| url =https://books.google.com/books?id=XZ2QB7bu5LwC&pg=PA670| accessdate =5 August 2010| year =2004| publisher =Synapse Info Resources| isbn =978-1-890595-66-1| page =5856}}
6. ^{{cite journal| vauthors = Yellapu RK, Mittal V, Grewal P, Fiel M, Schiano T| title = Acute liver failure caused by 'fat burners' and dietary supplements: a case report and literature review| journal = Canadian Journal of Gastroenterology| volume = 25| issue = 3| pages = 157–60| year = 2011| pmid = 21499580| pmc = 3076034| doi = 10.1155/2011/174978| url = }}
7. ^{{cite journal | last1 = Hsu | first1 = LM | last2 = Huang | first2 = YS | last3 = Chang | first3 = FY | last4 = Lee | first4 = SD | date = Jul 2005 | title = 'Fat burner' herb, usnic acid, induced acute hepatitis in a family | url = | journal = J Gastroenterol Hepatol | volume = 20 | issue = 7| pages = 1138–9 | doi=10.1111/j.1440-1746.2005.03855.x| pmid = 15955234 }}
8. ^Sanchez W, Maple JT, Burgart LJ, Kamath PS. Severe hepatotoxicity associated with use of a dietary supplement containing usnic acid. Mayo Clin Proc. 2006 Apr;81(4):541-4.
9. ^{{cite web|title=Safety Alerts for Human Medical Products > Lipokinetix|url=http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm172824.htm|work=MedWatch: The FDA Safety Information and Adverse Event Reporting Program|publisher=U.S. Food and Drug Administration|accessdate=5 December 2012|date=November 20, 2001|quote=FDA has received multiple reports of persons who developed liver injury or liver failure while using Lipokinetix. The product contains norephedrine (also known as phenylpropanolamine or PPA), caffeine, yohimbine, diiodothyronine, and sodium usniate.}}
10. ^Harris N. J. (1961), Honors Thesis, Clark University, Worcester, Massachusetts
11. ^Kreft, S. et Štrukelj, B. Reversed-polarity capillary zone electrophoretic analysis of usnic acid. Electrophoresis, 22:2755-2757 http://pubs.acs.org/doi/abs/10.1021/ac990198%2B

Biological role in lichens

Uses and properties

Safety

Pharmacology

Analytics

References

External links