Health Care Professional Information
Usnic acid is a secondary metabolite of lichens. Some species of lichens have been used in traditional medicine for pain relief, fever, and wound healing. Usnic acid is used as a preservative in cosmetic products. It demonstrated antioxidant (1), anti-inflammatory (2), antimicrobial (3) (4), antiproliferative and anticancer (5) (6) (7) (8), and dermal burn healing (9) properties in vitro and in animal models. A clinical study using a formulation of usnic acid and zinc showed effectiveness against genital human papillomavirus infection (10).
Over-the-counter supplements that contain usnic acid have been promoted for weight loss but scientific evidence is lacking (11). Misuse of usnic acid products has been associated with severe hepatotoxicity (12) (13) (14).
Usnic acid is found in Kombucha tea (12).
Lichens are not commonly consumed as food.
- Weight reduction
- Pain relief
Mechanism of Action
Usnic acid has two enantiomers (+)-usnic acid and (-)-usnic acid which are thought to have different biological activities. Studies show that (+)-usnic acid has antimicrobial (3) (4), anti-inflammatory (2), and cytotoxic (5) effects while (-)-usnic acid exhibits anti-protozoan properties (15). Usnic acid can induce oxidative stress and inhibit mitochondrial function in liver cells (16) (17) which may contribute to its hepatotoxicity. However, conflicting data indicate that usnic acid protects gastric cells from drug-induced oxidative damage (1). It may inhibit prostaglandin synthesis (2).
Usnic acid demonstrated antiproliferative effects against breast cancer cells independent of p53 activity (6). In lung cancer cells, usnic acid inhibited cell growth involving G0/G1 phase cell cycle arrest and induced cell death via mitochondrial membrane depolarization and induction of apoptosis (18).
Weight loss supplements containing usnic acid have been associated with severe hepatotoxicity (14).
Acute hepatitis is also attributed to the use of Kombucha tea, which contains usnic acid (12).
Liver damage with use of usnic acid-containing supplements (12) (14) (19).
Topical use may cause local irritation and allergic reactions (11).
Fulminant liver failure: Following use of usnic acid for weight loss in one woman that eventually required liver transplantation (13).
Anticoagulants: Theoretically, usnic acid may have additive effects with anticoagulant medications (14).
Cytochrome P450 3A4 substrates: Usnic acid induces CYP3A4 and can affect the intracellular concentration of drugs metabolized by this enzyme (20)
Herb Lab Interactions
In two case reports, usnic acid dramatically increased ALT, AST, ALK P, and total bilirubin levels, and also prolonged prothrombin time (14).
- Odabasoglu F, Cakir A, Suleyman H, et al. Gastroprotective and antioxidant effects of usnic acid on indomethacin-induced gastric ulcer in rats. J Ethnopharmacol. Jan 3 2006;103(1):59-65. doi: 10.1016/j.jep.2005.06.043
- Vijayakumar CS, Viswanathan S, Reddy MK, et al. Anti-inflammatory activity of (+)-usnic acid. Fitoterapia. Sep 2000;71(5):564-566.
- Francolini I, Norris P, Piozzi A, et al. Usnic acid, a natural antimicrobial agent able to inhibit bacterial biofilm formation on polymer surfaces. Antimicrob Agents Chemother. Nov 2004;48(11):4360-4365. doi: 10.1128/AAC.48.11.4360-4365.2004
- Weckesser S, Engel K, Simon-Haarhaus B, et al. Screening of plant extracts for antimicrobial activity against bacteria and yeasts with dermatological relevance. Phytomedicine. Aug 2007;14(7-8):508-516. doi: 10.1016/j.phymed.2006.12.013
- Koparal AT, Tuylu BA, Turk H. In vitro cytotoxic activities of (+)-usnic acid and (-)-usnic acid on V79, A549, and human lymphocyte cells and their non-genotoxicity on human lymphocytes. Nat Prod Res. Dec 2006;20(14):1300-1307. doi: 10.1080/14786410601101910
- Mayer M, O'Neill MA, Murray KE, et al. Usnic acid: a non-genotoxic compound with anti-cancer properties. Anticancer Drugs. Sep 2005;16(8):805-809.
- Kumar KC, Muller K. Lichen metabolites. 2. Antiproliferative and cytotoxic activity of gyrophoric, usnic, and diffractaic acid on human keratinocyte growth. J Nat Prod. Jun 1999;62(6):821-823. doi: 10.1021/np980378z
- O'Neill MA, Mayer M, Murray KE, et al. Does usnic acid affect microtubules in human cancer cells? Braz J Biol. Aug 2010;70(3):659-664.
- Nunes PS, Albuquerque RL, Jr., Cavalcante DR, et al. Collagen-based films containing liposome-loaded usnic acid as dressing for dermal burn healing. J Biomed Biotechnol. 2011;2011:761593. doi: 10.1155/2011/761593
- Scirpa P, Scambia G, Masciullo V, et al. [A zinc sulfate and usnic acid preparation used as post-surgical adjuvant therapy in genital lesions by Human Papillomavirus]. Minerva Ginecol. Jun 1999;51(6):255-260.
- Ingolfsdottir K. Usnic acid. Phytochemistry. Dec 2002;61(7):729-736.
- Chitturi S, Farrell GC. Hepatotoxic slimming aids and other herbal hepatotoxins. J Gastroenterol Hepatol. Mar 2008;23(3):366-373. doi: 10.1111/j.1440-1746.2008.05310.x
- Durazo FA, Lassman C, Han SH, et al. Fulminant liver failure due to usnic acid for weight loss. Am J Gastroenterol. May 2004;99(5):950-952. doi: 10.1111/j.1572-0241.2004.04165.x
- Sanchez W, Maple JT, Burgart LJ, et al. Severe hepatotoxicity associated with use of a dietary supplement containing usnic acid. Mayo Clin Proc. Apr 2006;81(4):541-544. doi: 10.4065/81.4.541
- Wu J, Zhang M, Ding D, et al. [Effect of Cladonia alpestris on Trichomonas vaginalis in vitro]. Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi. 1995;13(2):126-129.
- Han D, Matsumaru K, Rettori D, et al. Usnic acid-induced necrosis of cultured mouse hepatocytes: inhibition of mitochondrial function and oxidative stress. Biochem Pharmacol. Feb 1 2004;67(3):439-451. doi: 10.1016/j.bcp.2003.09.032
- Moreira CT, Oliveira AL, Comar JF, et al. Harmful effects of usnic acid on hepatic metabolism. Chem Biol Interact. Apr 25 2013;203(2):502-511. doi: 10.1016/j.cbi.2013.02.001
- Singh N, Nambiar D, Kale RK, et al. Usnic acid inhibits growth and induces cell cycle arrest and apoptosis in human lung carcinoma A549 cells. Nutr Cancer. 2013;65 Suppl 1:36-43. doi: 10.1080/01635581.2013.785007
- Yellapu RK, Mittal V, Grewal P, et al. Acute liver failure caused by 'fat burners' and dietary supplements: a case report and literature review. Can J Gastroenterol. Mar 2011;25(3):157-160.
- Mannering GJ, Shoeman JA. Induction of murine cytochrome P4503A by the lichen constituents usnic and vulpinic acids. Drug Metab Dispos. Jul-Aug 1994;22(4):663-665.
How It Works
Bottom Line: There is no scientific evidence to support the use of usnic acid for weight loss. Supplements containing usnic acid are associated with severe liver toxicity.
Usnic acid is a compound found in lichens. It has been used as a preservative in moisturizing creams, and as an ingredient in toothpastes, mouthwashes, and deodorants because of its antibacterial properties. Dietary supplements that contain usnic acid are promoted for weight loss but scientific evidence is lacking. The supplements have also been associated with liver toxicity.
- Weight loss
This claim is not supported by scientific evidence.
Usnic acid has been used in moisturizing creams, toothpastes, mouthwashes, and deodorants because of its antibacterial properties.
In one clinical study, an intravaginal formulation of usnic acid and zinc showed favorable results when used as an adjunct to radiosurgery in patients with human genital papillomavirus infection.
This claim is not backed by scientific studies.
- Pain relief
This use is not supported by scientific evidence.
Weight loss supplements containing usnic acid are associated with severe liver toxicity.
Do Not Take If
You are taking anticoagulants: Theoretically, usnic acid may have additive effects with anticoagulant medications.
You are taking drugs that are substrates of Cytochrome P450 3A4: Usnic acid can decrease the effects of such drugs.
- Usnic acid can cause liver damage when used in high doses.
- Allergic reactions have been reported with topical use.
Last updated: November 20, 2014