Review of Usnic Acid andUsnea BarbataToxicity

Abstract

Usnic acid is a prominent secondary lichen metabolite that has been used for various purposes worldwide. Crude extracts of usnic acid or pure usnic acid have been marketed in the United States as dietary supplements to aid in weight loss. The US Food and Drug Administration (FDA) received 21 reports of liver toxicity related to the ingestion of dietary supplements that contain usnic acid. This prompted the FDA to issue a warning about one such supplement, LipoKinetix, in 2001 (http://www.cfsan.fda.gov/~dms/ds-lipo.html). Subsequently, usnic acid and Usnea barbata lichen were nominated by the National Toxicology Program (NTP) for toxicity evaluations. At present, a toxicological evaluation of usnic acid is being conducted by the NTP. This review focuses on the recent findings of usnic acid-induced toxicities and their underlying mechanisms of action. KeywordsWeight loss dietary supplement; usnic acid and Usnea barbata toxicity

Usnic acid biological activity: history, evaluation and usage

“…Ramalina was the first genra to isolate usnic acid in 1843, after one year it was distinguished from other substances and get its name, later by nine decades the chemical structure was determined. 4 Castle and Kubsch were the first to report that UA is produced within the mycobiont (fungal part) of the lichen and then make a layer on the surface of the photobiont. 5 Lichens' usnic acid content relies on several factors: geographic location, the time of summer solstice, insolation, and temperature.…”

“…Song Lo tea", it was used for cleaning the liver, treating malaria, healing wounds and snake bite with common dose 6-9g of dried lichen, it was classified as rare medication. 4 For long time it was used as antibacterial in many nations and being utilized as a modern pharmaceutical till the penicillin antibiotics were discovered. 3 Where it was used as main agent or as preservative for treating pulmonary tuberculosis, pain, fever, wounds, athlete's foot, deodorants, and herbal tinctures, with different names regarding the country, in Germany "Monogram", in Finland, "Rosalina Thrust" and in Argentina, "Barba del la Piedra".…”

“…It is estimated that lichens cover around 8% of the earth surface with more than 17,000 species and over 800 lichen products are known. 4 A lot of researchers were interested in lichens products, such as polysaccharides, proteins and secondary metabolites regarding their biological activities as medications, food supplements, dyes, where the most famous lichen secondary metabolite is usnic acid (UA). 2 First time to isolate Usnic acid (UA) from lichen metabolite was in 1844, and from that year a lot of studies were done on UA, and it became commercially available.…”

“…3 Where it was used as main agent or as preservative for treating pulmonary tuberculosis, pain, fever, wounds, athlete's foot, deodorants, and herbal tinctures, with different names regarding the country, in Germany "Monogram", in Finland, "Rosalina Thrust" and in Argentina, "Barba del la Piedra". 4 From the end of 2 nd world war to 1950s, the work on UA focused on its antimicrobial activity. Then it was activated again in 1980s due to the problem bacterial resistance.…”

Antimicrobial activity of usnic acid on Squamarina lentigera (Lichenized Ascomycetes) lichen species

“…The amount of usnic acid was found as 2.47% of the dry lichen weight in S. lentigera. (25,26), and its potential use in the sterilization of surgical implants is being investigated (6,27). …”