Melanin from the Lichens Cetraria islandica and Pseudevernia furfuracea: Structural Features and Physicochemical Properties

Lichens are symbiotic photosynthesizing organisms with thalli formed by fungi and algae/cyanobacteria that possess high stress tolerance. One of the factors that contributes to the ability of a lichen to tolerate harsh environmental conditions is the presence of unique metabolites, including high-molecular-weight dark pigments termed melanins. The chemical composition and structure of lichen melanins remain poorly studied. We analyzed the elemental composition, the main functional groups, and the physicochemical properties of melanin extracted from Cetraria islandica and Pseudevernia furfuracea lichens. Based on the C/N ratio, this pigment is allomelanin. We also identified functional groups that provide photoprotective and antioxidant properties of melanin. Melanin synthesis might be an essential defense mechanism contributing to the survival of lichens under exposure to UV radiation.