Weigh 5.0 g of chopped Usnea longiflora into a 500 mL flask, and extract with 75 mL of ethyl acetate for 2 times, 4 h each time, and combine the extracts. Suction filtration, concentrated to 1/6~1/8 of the original volume, naturally cooled, crystallized, filtered off the mother liquor, and dried at 80°C to obtain the crude usnic acid. 30 times the amount of benzene-ethanol (volume ratio 1:1) mixed solvent was added to the crude product, refluxed for 2 h, filtered while hot, the filtrate was concentrated to 1/5 of the original volume, and crystals were precipitated by cooling. Dry at 80 ℃, recrystallize twice with ethyl acetate, and the obtained relatively pure pale yellow needle crystal is the fine usnic acid.
Usnic Acid acts as an antibacterial and antifungal agent, and are often seen used in cosmetics and facial application chemicals.
Usnic acid is used as fragrance; preservative in deodorants; in anti ac ne formulations; antibiotic for topical application.
(+)-Usnic acid has been used to study the following:
- The mechanism of its antimicrobial activity in bacterial cells.
- Its ability as an antibiofilm agent against Group A Streptococci (GAS).
- Its ability as a potent anti-virulent compound against Candida albicans.
- The mechanism of its toxic effect on hepatocytes.
- Its ability to inhibit the motility of human lung cancer cells.
(+)-Usniacin is a primary reference substance with assigned absolute purity (considering chromatographic purity, water, residual solvents, inorganic impurities). The exact value can be found on the certificate. Produced by PhytoLab GmbH & Co. KG.
mic: 0.05 μg/62.5 μl to 3.1 μg/62.5 μlmicroorganisms can colonize a wide variety of medical devices, putting patients at risk for systemic and local infectious complications, including local-site infections, endocarditis, and catheter-related bloodstream infections. (+)-usniacin is a secondary lichen metabolite that possesses antimicrobial activity against various planktonic gram-positive bacteria.
Usnic acid is a component of lichens, also used as a
topical antibiotic. Allergic contact dermatitis from
lichens occurs mainly occupationally in forestry and
horticultural workers, and in lichen pickers.
(+)-usniacin showed antimicrobial activity against the same microorganisms as that of acetone extract. among the three analogues it was the most active one having quite low mic values. furthermore, (+)-usniacin did not show any activity against a. hydrophila and b. cereus whereas (d)-usnic acid did. on the other hand, (+)-usniacin was active against y. enterocolitica whereas (d)-usnic acid was not active .
This very weak acid is the natural form which is recrystallised from Me2CO, MeOH or *C6H6. At 25o it is soluble in H2O (<0.01%), Me2CO (0.77%), EtOAc (0.88%), MeOCH2CH2OH (0.22%) and furfural (7.32%). [Curd & Robertson J Chem Soc 894 1937, Barton & Brunn J Chem Soc 603 1953, resolution: Dean et al. J Chem Soc 1250 1953, synthesis: Barton et al. J Chem Soc 538 1956, Beilstein 18/5 V 586.]
 tay t, türk ao, yilmaz m, türk h, kivanç m. evaluation of the antimicrobial activity of the acetone extract of the lichen ramalina farinacea and its (+)-usnic acid, norstictic acid, and protocetraric acid constituents. z naturforsch c. 2004 may-jun;59(5-6):384-8.
 ghione m, parrello d, grasso l. usnic acid revisited, its activity on oral flora. chemioterapia. 1988 oct;7(5):302-5.