Antioxidant activities of fungi inhabiting Ramalina peruviana: insights on the role of endolichenic fungi in the lichen symbiosis

Apart from the fungal component (the mycobiont), other fungi reside inside lichens. Referred to as “lichen-associated fungi” or “endolichenic fungi” (ELF), these microorganisms have a poorly understood role in the lichen symbiosis. In this study, 11 morphoculturally-distinct ELF were isolated from the fruticose lichen Ramalina peruviana and identified as belonging to the genera Colletotrichum (1), Daldinia (3), Hypoxylon (1), Nemania (1), Nigrospora (1), and Xylaria (4). Each ELF was grown in two separate setups – submerged and solid-state fermentation – and were extracted with ethyl acetate for their secondary metabolites. Similarly, metabolites from the lichen host were also extracted. Among the 11 isolates, crude culture extracts of Nemania primolutea grown via the solid-state fermentation setup exhibited the highest radical scavenging activity (RSA = 89.7%), followed by Colletotrichum eschscholtzii grown using similar fermentation type (RSA = 80%). In contrast, extracts of the lichen host exhibited a slightly lower RSA (= 45.89%). Results showed that endolichenic fungi exhibited antioxidant activities greater than the lichen host, and possibly contributes to the protection of the lichen symbiosis through the synthesis of antioxidant compounds