Usnea

Botanical Name: Usnea spp.

Family: Usneaceae

Parts Used: Whole lichen

Constituents: Usnic acid, usnaric acid, thamnolic acid, lobaric and stictinic acids. Atronorine, polysaccharides(1)

Principal Actions: Expectorant, Antimicrobial, antifungal, immunostimulant.

Pharmacy: Tincture of dried whole plant 1:2 95% alcohol.(hot extraction - see below)

Usnea spp. are ubiquitous lichens throughout the North West, which probably due to its high annual precipitation has a great diversity of the genus, especially the epiphytic varieties. These grow in delicate pale green tufted strands of filaments, hanging prolifically from the branches of trees in old growth forest - the appearance giving rise to the common name Old Man's Beard. Medicinally the Usneas have been used for centuries, in both Chinese and Unani medicine. It remains a somewhat neglected remedy, although it has some unique contemporary applications, particularly as a respiratory antimicrobial for atypical pneumonias.

BOTANY

Taxonomically the genus is difficult to deal with for the non-lichen expert. Typically, the epiphytic Usneas have a double thread filament construction, with an inner core, variously coloured from white to yellow, which can be exposed by gently pulling the outer ends of a strand of the plant. Reproduction is by soredia, but taxonomical classification depends upon many factors besides the reproductive morphology. (2). The epiphytic species include U. hirta, U. longissima. U. cornuata, U. hespirata, & U. wirthii.

HARVESTING

The North Western Usneas are predominantly found in old growth forest from low to upper middle elevations on both sides of the Cascades. The adhesion of the lichens to the tree bark is somewhat tenuous, and merely an anchorage for elevated exposure to the moist air. Local herbalists prefer not to disturb the plants that are growing from trees, there usually being abundant material on the ground for harvesting after a storm. It may be gathered from the ground at any time. The plant is inherently dry and brittle, little additional drying is usually required.

PHARMACOLOGY

The predominant active constituent is usnic acid. Usnic acid is a diphenyl ether linked polyphenolic acid, which is virtually insoluble in water and ethanol - solubilities at 25C in g/100ml: water <0.01, acetone 0.77, ethyl acetate 0.88, ethanol 0.02, furfuryl 7.32.(3) Extraction is therefore problematic - some manufacturers use a hot concentrated ethanolic process, it being possible that the solubilisation of usnic acid is altered as other constituents move into solution. Other constituents include d-arabitol and unidentified polysaccharides - the latter have been conjectured to be responsible for the immunomstimulating effects of the lichen. (2) If so, then this is a case for a double phase extraction, primarily water followed by a hot ethanolic stage.
(NB! Heating ethanol requires special chemical apparatus to avoid danger of fire)

Usnic acid (formula above) attracted interest for its antimicrobial properties during the search for antibiotic compounds from fungal and other plant sources during the second world war. In vitro, usnic acid completely inhibits human tuberculosis bacillus in concentrations of 1:50,000; it is also effective in vitro against Streptococcus, Staphylococcus and Pneumococcus at dilutions of 1:20,000(1).

ETHNOBOTANY

The principal Indian traditional uses of Usneaspp. are confined to topical preparations for antisepetic dressings wound healing, although the plant was for a variety of economic purposes.(4)

MEDICINAL USES

Today Usneas are used primarily as respiratory anti-microbial agents with an immunostimulant aspect to their activity. Usnea is effective in TB, as well as other lower respiratory infections. It has also been used as topical antimicrobial in vaginal infections due to Trichomonas, Chlamydia, and Candida albicans. Because of solubility issues, the dried powdered herb can be taken (in capsule form) or dusted on to affected parts for topical use. The remedy has been clinically used with good effect in atypical pneumonias, especially those due to Mycoplasma pneumoniae. In this case it may be given in given in combination with Osha (Ligusticum porterii) and White sage (Salvia apiana). (5)

REFERENCES

(1) Hobbs C, Usnea the Herbal Antibiotic. Botanica Press 1990.

(2) Pittam S, Pendent Usnea (Lichens; Ascomycetes; Parmeliaceae) in Western Oregon: Taxonomy; Morphological Characters; and Geographic Dstribution. Thesis, Oregon State University.1995

(3) Chem Abstracts; Vol 96, 139704h.

(4) American Indian Ethnobotany Database: http://www.umd.umich.edu/cgi-bin/herb/

(5) Noble R, MD. Personal Communication, Oregon, 1996.

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