Antibacterial potential of Antarctic Lichens against Human Pathogenic Gram Positive Bacteria

Abstract

Extracts from five Antarctic lichens (L3, Stereocaulon alpinum;L5, Ramalina terebrata;L6, Caloplaca sp.;L8, Lecanora sp.;and L17, Caloplaca regalis) were tested for antimicrobial activities against several clinically important microbes by disk diffusion. The minimum inhibitory concentration (MIC) of each extract was determined by broth dilution method. Extracts from L3, L5, L6 and L8 were active against two Gram(+) strains. B. subtilis was more sensitive to lichen extracts (except L5) than S. aureus. The MIC of lichen extracts against B. subtilis and S. aureus was observed from 36.7 ？0.3 to 953.8？85.8 ？g ml-1 and 68.5？0.6 to >1000 ？g ml-1, respectively. Comparisons of MIC values of Antarctic lichen crude extracts to previously published MIC values of some reported lichen metabolites against Gram(+) bacteria indicated that Antarctic lichens might be an enriched source of effective antibacterial agents against clinically relevant Gram(+) species.