Lecanoric acid is an orcinol depside found in a broad range of lichen and fungal species. Structurally, lecanoric acid is a dimer of orsellinic acid. Lecanoric acid is a broad antimicrobial agent, exhibiting more potent activity against bacteria than fungi. Lecanoric acid is also active as an immunomodulator, antioxidant, an inhibitor of histidine decarboxylase and is involved in gene activation/suppression. Lecanoric acid is an important standard in the chemotaxonomy of lichens.