S Malhotra, R Subban, A Singh
lichens, pharmacology., phytochemistry, traditional medicine
S Malhotra, R Subban, A Singh. Lichens- Role in Traditional Medicine and Drug Discovery. The Internet Journal of Alternative Medicine. 2007 Volume 5 Number 2.
Lichens represent a unique division in the plant kingdom. They have been used in Traditional systems of medicine including Traditional Indian Medicine (TIM), Traditional Chinese Medicine (TCM), Homeopathic and Western Medical Herbals. Lichens have been used in the treatment of diverse diseases like arthritis, alopecia, constipation, kidney diseases, leprosy, pharyngitis rabies, infection, worm and infestation. The medicinal utility of lichens is regarded to presence of secondary compounds like of usnic acid and atranorin. Animal investigations on lichens have demonstrated antimicrobial, antitumor and immunomodulaor activity. One of the reasons for exploring biological compounds in lichens is the potential for medical use. However, much work remains to link medical effects with specific lichen species.
The Lichen Division is comprised of at least 8 orders, 45 families, and 6,000 species. Information on the edible and medicinal uses of the lichens is scattered (Chevallier, 1996). Many lichens are known to have potent antibiotic properties, and many are edible. However, some lichens do contain toxic substances, so you should not graze randomly on them (Agelet & Joan, 2003).
Lichens in folk and traditional medicine
“Doctrine of Signatures” written in the 15th century stated “A plant could treat a diseases it most looked like” This formed the basis of phyto-therapeutics in traditional systems of medicines like Traditional Indian Medicine (TIM) or Ayurveda, Traditional Chinese Medicine (TCM), and Western Medical Herbalism (Bown, 2001). Interestingly enough, the word lichen is derived from Greek word ‘Leprous' and refers to use of lichens in treating skin diseases due to their peeling-skin appearance. Lichen like
Medicinal uses of lichens are linked with folklore. The medicinal use of lichens can be traced back to the 18th dynasty (1700-1800 BC) when
People of Northern California used
Spanish folk medicine has documented use of lichens in various medical aliments. Decoction of
Reindeer lichens are important medicinal agents.
Phytochemical and pharmacological investigations
Lichen metabolites exert a wide variety of biological actions including antibiotic, antimycobacterial, antiviral, anti-inflammatory, analgesic, antipyretic, antiproliferative and cytotoxic effects. Even though these manifold activities of lichen metabolites have now been recognized, their therapeutic potential has not yet been fully explored and thus remains pharmaceutically unexploited (Müller, 2002). The utility of lichens is due of range of secondary compounds produced by them (Boustie & Grube, 2005).
Antibiotic properties of the lichens are of special interest to the scientists (Lawrey, 1986). According to one estimate, 50 % of all lichens have antibiotic properties (Sharnoff, 1997). Burkholder (1944) was pioneer initiating research on lichens as antibacterial agents. He tested 42 lichens for antibiotic property and 27 were reported to inhibit growth of bacteria (Burkholder et al 1944; Bylicka, 1952; Vartia, 1973).
Usnic acid isolated from lichens from south Spain has high activity against Gram-positive bacteria (Rowe et al. 1999). Acetone, diethyl ether and ethanol extracts of the lichen
Alectosarmentin, (-)-usnic acid, physodic acid and 8'-O-ethyl-beta-alectoronic acid isolated from the alcoholic extract of the lichen
The acetone and methanol extracts of
3-hydroxyphysodic acid isolated from
Parietin, anthraquinone isolated from methanol extract of
Usnic acid isolated from
Phenolic constituents from the lichen
Pannarin inhibited cell growth and induces cell death in human prostate carcinoma DU-145 cells (Maier et al. 1999).The orcinol derivatives tenuiorin and methyl orsellinate present in extract of
Heteroglycans and a beta-glucan isolated from
Methanol extracts of
Recent phytochemical investigations on lichens
Two tridepsides (2,4-Di-O-methylgyrophoric acid and 2,4,5-tri-O-methylhiascic acid) have been isolated from
A new red anthraquinone, draculone, has been isolated from the corticolous tropical lichen