Active Compounds and Bacteria Harbouring Capacity of Lichens and Its Medicinal Use in Bacterial and Cancer Infections

Lichens are composite organisms formed upon symbiotic association of fungi and algae doing photosynthesis (blue green algae). Lichenized fungi produce unique secondary metabolites which bears a wide spectrum in biological activities viz., anti-HIV, production of antibiotics, anti-protozoan, anticancer etc. This review focuses primarily on the antibacterial activity of lichen’s secondary chemicals related to major antibacterial activity and highlights of each study. The literature published clearly demonstrates that the lichen extracts and their constituent compounds have potential of significant inhibitory activity against various pathogenic bacteria viz., Bacillus cereus, Bacillus subtilis, Chrysobacterium indolthecium, Clavibacter michiganensis subsp. Michiganensis, Enterococcus faecalis, Erwinia carotovora sub sp. carotovora, Escherichia coli, Methicillin-resistant S. aureus, Pseudomonas aeruginosa. Pseudomonas cichorii, Pseudomonas savastoni pv. Fraxinus, Pseudomonas syringae pv. syringae, Pseudomonas vesicularis, Staphylococcus aureus, Staphylococcus aureus, Streptococcus pneumoniae, Xanthomonas axanopodis pv. Malvecearum, Xanthomonas hortanum pv. pelargonii, Xanthomonas phaseoli, Yersiniapseudotuberculosis, even at low concentrations. The literature records however shows no studies reported anything on the specific mechanism of action against pathogenic bacteria. Lichens harbours many biologically active compounds in which less numbers have been experimentally tested. It needs very deep studies for search of active compounds. It needs to do more clinical trials and search of mechanism of action for potent compounds in lichens.