ABSTRACT
Lichens represent a unique association of two or more organisms. This coexistence is the result of symbiosis. In the past lichens were used worldwide as a source of bioactive compounds in many different cultures. The records of medical use of lichens are coming from almost all continents. The lichen Pseudevernia furfuracea belongs to the lichenized fungi and is known as the tree moss in traditional medicine. P. furfuracea produces secondary metabolites such as atranorin, chloratranorin, olivetoric acid (depsides) and physodic acid, 3-hydroxyphysodic acid, and physodalic acid (depsidones). All of these compounds were probably the reason why humans in the past used lichens to treat diseases. Nowadays there have been studies of several secondary metabolites in which their biological activities, such as antifungal, anti-inflammatory, antimicrobial, antioxidant, photoprotective, oxidative, cytotoxic and anti-cancer, have been studied. Cancer is still one of the major causes of death worldwide. The pharmacological industry is still looking for natural plant substances, which are a source of bioactive compounds with application in medicine in the fields of pharmacology and oncology. There is still a lack of information about lichen secondary metabolites, and their potential is still undiscovered.
