Botany of Usnea Lichens
Lichens are symbiotic organisms of fungi and algea that comprise about 17,000 species, which synthesize numerous metabolites. Lichens and their metabolites exert a wide variety of biological functions and have beend used in perfumery, cosmetics, ecological applications, and pharmaceuticals. The significance of lichens and their metabolites was summarized in a review article by Huneck. It is estimated that lichens cover approximately 8% of the earch surface. Usnic acid has been identified in many lichen genera including species of Alectoria, Cladonia, Evamia, Lecanora, Parmelia, Ramalina, and Usnea. Traditionally, Usea species such as the pendulous “beard” Lichens, U, Barbata, U. florida and U. longissima have been used a source of usnic acid in herbal medicine, and their usnic acid content ranges from 1-3% of dry weight. Usnea sold in the US is often sold as U. barbata but can consist of serveral Usnea species, and if collected from American forests is unlikely to contain U. barbata, since this species is not native to North America. Usnic acid is synthesized within the mycobiont (fungal part) of the lichen and is then deposited onto the outer surface of the photobiont.
History of use of Usnea lichens and Usnic acid
The first recorded use of the usea speicies in Traditional Chinese Medicine (TCM) dates to 101 BC., when it was used as an antimicrobial agent under the Chinese name of Song Lo. Song Lo tea or decoction for internal and external use has also been recorded for detoxification of the liver, treatment of malaria, wounds, snake bite, cough and so on. The common TCM dosage are 6-9g od dried lichen, which correspons with approximately 60-120mg usnic acid per day. However, despite its long history, Song Lo is classifed as a rarely used herb in TCM (only 500 are commonly used among over 6000 herbs recorded in TCM)
usnea species have been used as antimocrobia agents in many countries and were being developed as a modern pharmaceutical just prior to hte advent of the penicillin antibiotics. The crude extracts of usnic acid rich lichens (eg. Usnea species) have been used throughtout the world to treat various ailments, such as pulmonary tuberculosis, pain, fever, wounds, athlete’s foot, and other dermal lesions. They have also been used as expectorants, in antibiotic salves, deodorants, and herbal tinctures.
Application of Usnic Acid
Thus Usnea species or purified usnic acid are currently constituents in a variety of products worldwide. For example, lichen extract and purifed usnic acid have been widely used in perfumery, cosmetics, sunscreens, and personal hygiene products such as toothpaste, mouthwash, shampoo and deodorant.
In Germany, pure usnic acid has been formulated and used in cosmetics and pharmaceuticals under the trade names of “Omnigran a, Granobil, and Usnagren A”.
In Finland, “ramalina thrausta” was used internally to treat sore throat and thoothache and extermally to treat wounds and athlete’s foot.
In Italy, Usnic acid has been used in vaginal creams, food creams, powders and shampoo.
In Argentian, “Barba del la Piedra” (Usnea densirostra) has been sold to treat many ailments.
In these preparations, usnic acid is employed either as the active principle or has functioned as preservative.
In the USA, Usnea can be obtained in bulk powder or as dried lichen from serveral herbal supply companies.