Biological activities of lichen extracts

The challenge for today’s pharmaceutical industry lies in the discovery and development of new pharmacologically active molecules. Similar to higher plants, lichens are important sources of biologically active compounds. For a long time, some species of lichens have been used in traditional medicine in the treatment of numerous infectious diseases. The aim of this study was to analyze four previously uninvestigated lichen species and test their metabolites for antioxidant, antibacterial, and anticancer activity. Three of the lichens, Xanthoparmelia mexicana, Acarospora socialis, and Lobothallia praeradiosa were obtained from Joshua Tree National Park in Southeastern California, whereas the fourth species, Xanthomendozia fallax, is Native to the Black Hills, South Dakota. The antioxidant activity of lichen extracts was assessed using the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay. As DPPH is a well-known radical and scavenger for other radicals, it is commonly used as indicator of the radical nature of antioxidants. The crude ethanol extract from A. socialis showed a significant free radical scavenging activity of 88% after exposure for 60 min. The crude acetone and ethyl acetate extracts demonstrated encouraging antibacterial activity against gram-positive bacteria. The anticancer activity assay demonstrated that the crude acetone extract of L. praeradiosa resulted in death of 66% of MCF-7 cells. Results of all four lichen species will be presented and discussed. The most promising lichen(s) will be subjected to further studies to establish their usefulness for biomedical applications such as treatment of respiratory and urinary tract infections.