HPLC-QTOF-MS/MS-based metabolomic profiling combined with chemometric analysis links lichen metabolites to...

Lichens are a rich source of bioactive secondary metabolites with potential anti-inflammatory properties. This study involved the comprehensive phytochemical profiling of 39 lichen species collected in eastern Poland using HPLC-QTOF-MS/MS, combined with chemometric analysis and biological activity testing. After data processing, a total of 91 compounds were identified, with depsides and depsidones constituting the dominant chemical classes. Multivariate analyses (PCA and PLS-DA) revealed distinct metabolomic patterns among the species and highlighted the relationship between metabolite composition and biological activity. The anti-inflammatory potential of lichen extracts was evaluated in LPS-stimulated macrophages by measuring the levels of intracellular reactive oxygen species (ROS), nitric oxide (NO) and cyclooxygenase-2 (COX-2) activity. Most extracts significantly reduced ROS levels, indicating a consistent antioxidant effect. In contrast, modulation of NO and COX-2 was more variable and generally less pronounced. Chemometric analyses suggested that multiple metabolites contribute to the observed anti-inflammatory activity, with evidence of an inverse relationship between ROS reduction and COX-2 inhibition. Although some compounds were found to be associated with biological effects, the results indicate that these effects are likely to be driven by the complex interactions within the extracts rather than by the action of individual constituents. Overall, lichens emerge as promising sources of anti-inflammatory agents, primarily acting through antioxidant mechanisms.