Background: Lichens play an important role in many ecosystems and exist as a symbiotic
association between fungi and algae or cyanobacteria. This symbiosis results in the production of
unique secondary metabolites known as lichen substances, which arise within the thalli and are typically
in crystal form on the surface of the fungal hyphae. Recently, lichens and their secondary metabolites
have been receiving increased attention due to their nutritional value and pharmaceutical
Objectives: This review aims to cast a light on the importance and variety of common lichen substances
(secondary metabolites), which are investigated along with their historical and contemporary
applications, use in environmental research and discussion of the commercialisation of lichens-based
Methods: The literature, including research and review articles, was analysed and the information
was compiled to provide a complete review of Lichens. A desk-based study to elucidate the role of
lichens in commercial products was also undertaken.
Results: The analysis of metabolites, mostly secondary metabolites, has yielded a wide range of interesting
compounds with biological activities from antimicrobial to anticancer. 31 of these compounds
are discussed in detail. Further, the nutritional value of lichens is identified alongside a role
in environmental monitoring and a number of commercialised lichen-based products are located.
Conclusion: Lichens are found on every continent and have a history of use as food, medicine, dyes
and livestock feed. The pharmaceutical potential of lichens is high and several companies are now
attempting to commercialise these unique attributes.