The phenolic composition and antioxidant capacity of four Tunisian lichen species, Cladonia rangiformis, Flavoparmelia caperata, Squamarina cartilaginea and Xanthoria parietina, were determined in order to provide a better understanding of their lichenochemical composition. Powdered material of F. caperata was the richest in total phenolic content (956.68 μg GAE g−1 DW) and S. cartilaginea in proanthocyanidin content (77.31 μg CE g−1 DW), while the acetone extract of X. parietina showed the highest flavonoid content (9.56 μg CE g−1 DW). The antioxidant capacity of all lichen extracts and crude material was evaluated by DPPH. scavenging, iron‐chelating, and iron‐reducing powers. Results showed that methanol extracts of S. cartilaginea had the highest DPPH. antioxidant capacity (IC50=0.9 μg mL−1) and the highest iron‐reducing power was attributed to the acetone extract of this species. All extracts of all species were further screened by Fourier‐transform infrared spectroscopy (FT‐IR) and nuclear resonance spectroscopy (NMR); results showed an abundance of phenols, aromatic compounds, and fatty acids. Overall, our results showed that the investigated species are a rich source of potentially bioactive compounds with valuable properties.

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The lichen's special symbiotic structure enables it to produce bioactive substances. They have historically been recognized for their aesthetic and medicinal benefits. Furthermore, in recent years, they have performed in various fields, including perfumery, dyeing, and pharmacology due to their rich secondary metabolites. From our study, four compounds were isolated from organic extracts of Parmotrema hypoleucinum, Roccella phycopsis, and Xanthoria parietina and identified by spectroscopic investigation as atranorin, (+)-iso-usnic acid, methyl orsellinate, and parietin, respectively. The anti-inflammatory effects of lichens extracts, and pure compounds were evaluated on RAW 264.7 macrophages cells at different concentrations. At 25 μg/mL all treated samples did not show any effect on cell viability. Atranorin and (+)-iso-usnic acid showed an inhibitory effect on nitric oxide (NO) levels in lipopolysaccharide (LPS)-stimulated macrophages. Nitric oxide (NO) production was measured using Griess reagent, atranorin and (+)-iso-usnic acid showed a high anti-inflammatory potential (75.99 % and 57.27 % at 25 μg/mL). On the other hand, methyl orsellinate and the organic extracts of three lichens showed good anti-inflammatory activity ranging from 29.16 % at 25 μg/mL to 86.91 % at 100 μg/mL.