In vitro analysis of antibacterial and antifungal potential of lichen species of Everniastrum cf vexans, Parmotrema blanquetianum, Parmotrema reticulatum and Peltigera laciniata

Abstract

Infectious diseases caused by bacteria, fungi and others microorganism remain a major threat to public health, despite tremendous progress in human medicine. Their impact is particularly great in developing countries because of the relative unavailability of medicines and the emergence of widespread drug resistance. Interests in natural products with antimicrobial properties have evolved as a result of current problems associated with the use of antibiotics. Plant derived antimicrobial compounds have been the source of novel therapeutics for many years. This may be due to the fact that these compounds show the structural intricacy and chemical diversity required to interact with antibacterial protein targets and provide vast opportunities for new drug development.1,2 Just as the higher plants have been used in folk medicine, lichens have also been used in food and in folk medicine in many countries over a considerable period of time. A lichen is a composite organism that emerges from algae or cyanobacteria (or both) living among filaments of fungus in a mutually beneficial (symbiotic) relationship. They represent taxonomically and physiologically a diverse group of organisms. Lichens produce a number of characteristic secondary metabolites called lichen substances, which seldom occur in other organisms. Depsides and depsidones are among the most common secondary metabolites produced by the fungal symbiont. The lichens and their metabolites are shown to possess various biological activities such as antimicrobial, antiviral, antiprotozoal, enzyme inhibitory, insecticidal, antitermite, cytotoxic, antioxidant, antiherbivore, wound healing, analgesic and anti‒inflammatory.1‒5 Lichens are very abundant organisms and can withstand hostile environmental conditions; therefore, they are able to colonize diverse ecosystems. It is estimated that there are between 17.500 and 20.000 species of lichens known in the world, with about 1.500 lichen‒shaped fungi.6 In Venezuela, there are 1.320 species reported by and probably around an estimated 4.000 are expected to be discovered of which 85% are concentrated in the Venezuelan Andes, which represents one of the most rich and diverse regions of the world. Thus the aim of the present study was investigate the antibacterial and antifungal potential of four lichens from Venezuelan Andes i.e., Everniastrum cf. vexans, Parmotrema blanquetianun, Parmotrema reticulatum, Peltigera laciniata.7‒9