Antioxidant activity of some lichen metabolites.

Antioxidant activity of several classes of lichen metabolites were assessed in the in vitro superoxide radical (SOR), nitric oxide radical and 2,2-diphenyl-1-picrylhydrazil radical scavenging assays. The despsides sekikaic acid and lecanoric acid showed promising antioxidant activity in SOR assay with IC₅₀ values of 82.0 ± 0.3 µmol and 91.5 ± 2.1 µmol, respectively, while the depsidone lobaric acid exhibited an IC₅₀ value of 97.9 ± 1.6 µmol, all relative to the standard, propyl gallate (IC₅₀ = 106.0 ± 1.7 µmol). One of the most abundant mononuclear phenolic compounds, methyl-β-orcinol carboxylate was found to be a potent NO scavenger (IC₅₀ = 84.7 ± 0.1 µmol), compared to the standard rutin (IC₅₀ = 86.8 ± 1.9 µmol).