Usnic acid

Structural formula
General
Surname	Usnic acid
other names	2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3 (2 H , 9b H ) -dibenzofurandion
Molecular formula	C 18 H 16 O 7
Brief description	yellow solid
External identifiers / databases
EC number	204-740-7
ECHA InfoCard	100.004.310
PubChem	24211
ChemSpider	22633
Wikidata	Q425335
properties
Molar mass	344.32 g mol −1
Physical state	firmly
density	1.54 g cm −3
Melting point	201-202 ° C
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 302
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Usnic acid is a natural antibiotic agent obtained from lichen species of the beard lichen genus ( Usnea ). The antimicrobial effect is mainly used for skin infections , but also in anti-dandruff preparations. It is also used for upper respiratory infections.

The compound is chiral , with both antipodes occurring in nature. The enantiomers each melt at 203 ° C. Racemization easily occurs when exposed to heat . A racemic mixture with a melting point of 197 ° C is formed.

Analytics

The content of usnic acid in an extract of lichen can be determined quantitatively by means of capillary electrophoresis .

Individual evidence

↑ ^a ^b ^c data sheet usnic acid (PDF) from Carl Roth , accessed on December 14, 2010.
↑ ^a ^b Data sheet (+) - Usnic acid from Usnea dasypoga at Sigma-Aldrich , accessed on October 16, 2016 ( PDF ).
↑ Oskar Widman: On the knowledge of usnic acid. In: Justus Liebig's Annals of Chemistry. 310, 1900, p. 230, doi : 10.1002 / jlac.19003100209 .
↑ ^a ^b Kuhnert-Brandstätter, M .; Friedl, L .: Contribution to the thermal analysis and polymorphism of optical antipodes: pantolactone, methadone and usnic acid, microchim. Acta 1979 II, pp. 97-110.
↑ Beilstein's Handbook of Organic Chemistry, EII 18 (1942) p. 241.
↑ Kreft, S. et Štrukelj, B. Reversed-polarity capillary zone electrophoretic analysis of usnic acid. Electrophoresis, 22: 2755-2757, doi : 10.1021 / ac990198 + .

[roth-1] ta sheet usnic acid (PDF) from Carl Roth , accessed on December 14, 2010.

[Sigma-2] Data sheet (+) - Usnic acid from Usnea dasypoga at Sigma-Aldrich , accessed on October 16, 2016 ( PDF ).

[3] Oskar Widman: On the knowledge of usnic acid. In: Justus Liebig's Annals of Chemistry. 310, 1900, p. 230, doi : 10.1002 / jlac.19003100209 .

[Kuhnert-Brandstätter1979-4] Kuhnert-Brandstätter, M .; Friedl, L .: Contribution to the thermal analysis and polymorphism of optical antipodes: pantolactone, methadone and usnic acid, microchim. Acta 1979 II, pp. 97-110.

[5] Beilstein's Handbook of Organic Chemistry, EII 18 (1942) p. 241.

[6] Kreft, S. et Štrukelj, B. Reversed-polarity capillary zone electrophoretic analysis of usnic acid. Electrophoresis, 22: 2755-2757, doi : 10.1021 / ac990198 + .