| Usnea: A Lesser-known Antibacterial | |
by Cathy Wong
Usnea barbata has a long history of use by North American herbalists,
particularly as an alternative for people who do not respond to the popular herb
Echinacea. A lichen hybrid of fungus and algae, Usnea is also known as
Old Man's Beard and Bear's Beard for its cascade of hair-like tendrils that hang
from tree trunks and branches.
There is preliminary evidence that usnic acid, the constituent of the Usnea species that has been studied most extensively, inhibits gram-positive bacteria such as streptococcus, staphylococcus, and mycobacteria. The organism Streptococcus pneumoniae is a major cause of bacterial pneumonia in adults, and a related organism, Streptococcus pyogenes, is responsible for the clinical condition pharyngitis, which is commonly referred to as strep throat. Usnea has not been shown to be effective against gram negative bacteria such as E. coli and salmonella.
How does Usnea fight bacteria?
Usnea appears to kill bacteria by disrupting their metabolic function. Specifically, it uncouples oxidative phosphorylation by acting on the inner mitochondrial membrane and also has ATP-ase activity. Both of these mechanisms ultimately kill bacterial cells by cutting off their energy supply. Unlike bacterial cells, human cells are less permeable to usnic acid and are not adversely affected.
What clinical conditions does Usnea treat?
Usnea is recommended by some herbalists and naturopathic doctors for acute and chronic lung infections, such as pneumonia, colds and flu, and as an adjunct to tuberculosis (TB) treatment. Although Usnea has not been supported in the research as being effective against viruses, there are many clinical examples that support its use. Herbalists often suggest Usnea as an alternative for people who are refractory to Echinacea.
Are there any known precautions?
Theoretically, caution is advised in people with autoimmune disease (e.g. rheumatoid arthritis, lupus), as Usnea may increase the action of the immune system.
Usnea has been shown to concentrate heavy metals from air pollution, so its growth environment is extremely important. When purchasing Usnea products, ensure that they are produced by a certified wild crafter.
A trained health practitioner should be always be consulted before trying any new treatment, since he or she can monitor the progress of health conditions and rule out the presence of serious illness. Avoid self-prescribing natural medicines; a herbalist or naturopathic doctor can recommend the most appropriate herb(s) for you after taking a history and conducting a physical examination.
References
Abo-Khatwa AN, al-Robai AA, al-Jawhari DA: Lichen acids as uncouplers of oxidative phosphorylation of mouse-liver mitochondria.
Cabrera C: Understanding Herbs: Uncommon antibiotics; Usnea and Lomatium. Nutrition Science News. 3;6;1998.
Herbal Medicine
Expanded Commission E Monographs. Blumental
M, Goldberg A, Brinckman J. American Botanical Council with Integrative Medicine
Communications First Edition. Newton, MA 2000
Saunders P: Lecture notes. Canadian College of Naturopathic Medicine. Fall 2000.
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