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

A. E. Rassabina1, O. P. Gurjanov1, R. P. Beckett2, and F. V. Minibayeva1,3a*

1Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of the Russian Academy of Sciences, 420111 Kazan, Russia

2School of Life Sciences, University of KwaZulu-Natal, 3209, Scottsville, South Africa

3Kazan (Volga Region) Federal University, 420008 Kazan, Russia

* To whom correspondence should be addressed.

Received February 20, 2020; Revised March 27, 2020; Accepted March 30, 2020
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.
KEY WORDS: melanin, lichen, IR spectroscopy, photoprotection, antioxidant activity

DOI: 10.1134/S0006297920050119