Endolichenic Fungi as a Source of Pharmaceutically Active Compounds

Around the world, fungi are found in a wide range of biological and environmental niches, where they serve as saprobes, symbionts, and pathogens. Among them, there are certain types of fungi that are capable of residing within the internal tissues of other organisms asymptomatically, without showing any outward signs of infection. One such example of them is the endolichenic fungi, which are a large and diverse group of fungi that live within the thalli of lichens. Similar to endophytic fungi, which live quiescently inside plant tissues, endolichenic fungi are also known to produce a diverse array of secondary metabolites with various bioactivities. A considerable number of these compounds are novel, with unique structures, or those that have been isolated from natural sources for the first time. Furthermore, there has been a renewed interest among the scientific community in the search for novel, natural product-based therapeutics, due to the threat of various emerging and re-emerging human diseases. It is against this background that the present chapter provides an overview of 108 different compounds that have been isolated from endolichenic fungi that possess one or more properties out of cytotoxic, antifungal, antioxidant, antibacterial, antiviral and anti-inflammatory activities, with an emphasis on novel compounds.