Lobaric acid is a depsidone metabolite that has been isolated from Stereocaulon lichen species with antioxidant, antiproliferative, antiviral, and enzyme inhibitory activites. It scavenges superoxide radicals in a cell-free assay (IC50 = 97.9 μmol) and inhibits proliferation in a panel of leukemia, colorectal, gastric, breast, ovarian, prostate, pancreatic, and lung cancer cell lines (EC50s = 15.2-63.9 μg/ml). Lobaric acid inhibits protein tyrosine phosphatase 1B (PTP1B; IC50 = 0.87 μM for the human recombinant enzyme) and production of 12(S)-HETE (Item No. 34570) by 12(S)-lipoxygenase (IC50 = 28.5 μM). In vivo, lobaric acid (250 μM) decreases lesion number, but not lesion diameter, in tobacco leaves infected with tobacco mosaic virus (TMV).
Cryptopleurine is an inhibitor of gene products associated with cell proliferation, survival, invasion and angiogenesis. It acts by targeting the NF-κB pathway.