SHORT COMMUNICATION The antimicrobial activity of substances derived from the lichens Physcia aipolia, Umbilicaria polyphylla, Parmelia caperata and Hypogymnia physodes Branislav Rankovic ´ Marijana Mis ˇic ´ Slobodan Sukdolak Received: 31 July 2007 / Accepted: 9 October 2007 / Published online: 18 October 2007 Ó Springer Science+Business Media B.V. 2007 Abstract In this study, in vitro antimicrobial activity of the physodic acid, usnic acid, atranorin and gyrophoric acid isolated from the lichens Hypogymnia physodes, Parmelia caperata, Physcia aipolia and Umbilicaria polyphylla, has been investigated. An antibiotic assessment was done against six bacteria (three Gram-positive and three Gram- negative) and eight fungi by determining the minimal inhibitory concentration (MIC) by the broth tube dilution method. The tested lichen substances inhibited growth of all the tested microorganisms. The bacteria showed a higher sensitivity against the tested fungi. The highest antimicrobial activity was found in the usnic acid of the Parmelia caperata lichen, where the lowest MIC was 0.0037 mg/ml against the Klebsiella pneumoniae (even lower than the one given by the streptomycin standard). The weakest antimicrobial activity was found in the phy- sodic acid, which inhibited most of the microorganisms in the concentration of 1 mg/ml. Generally, all the compo- nents had relatively strong antimicrobial activity against the tested microorganisms, among which were human and animal pathogens. This could be of significance for their use for pharmaceutical purposes. Keywords Antimicrobial activity Á Lichen compounds Introduction A lichen is a symbiotic organism consisting of a fungus (mycobiont) and a photosynthetic partner (photobiont), which can be either an alga or a cyanobacterium (Ahmadijan 1993). Lichens have been used in traditional medicine for years. In many European countries numerous species have been used for treatment of stomach diseases, diabetes, whooping cough, pulmonary tuberculosis, cancer treatment and skin diseases (Vartia 1973; Richardson 1988). Their use in medicine has later been justified by numerous papers in which their microbiotic activity had been found (Vartia 1973; Lauterwein et al. 1995; Ingo ´lfs- dottir et al. 1998; Mu ¨ler 2001). Lichens synthesize numerous metabolites, ‘‘lichen sub- stances’’ including aliphatic, cycloaliphatic, aromatic and terpenic components (Huneck and Yoshimura 1996). Numerous and various biological activities of lichens and their metabolites are known, such as: antiviral, antibiotic, antitumoural, antiallergic, antiherbivoral and they inhibit growth of plants as well as various enzymes (Lawrey 1986; Huneck 1999). It has been shown that the lichen extracts and their components have a distinguished antimicrobial activity (Vartia 1973; Ingo ´lfsdottir et al. 1998; Gulluce et al. 2006; Rankovic ´ and Mis ˇic ´ 2007, etc.). On the other hand, it is well known that microorganisms have very well developed resistance to many antibiotics. That creates a huge medical problem in the infective diseases treatment, so new sources of bioactive substances have been searched for, such as medicinal herbs, fungi and lichens (Hostettman et al. 1987; Karaman et al. 2003). Because of that, the aim of this paper is to isolate the lichen substances from the Physcia aipolia, Umbilicaria polyphylla, Parmelia caperata and Hypo- gymnia physodes lichens, and determine in vitro the B. Rankovic ´(&) Á M. Mis ˇic ´ Department of Biology, Faculty of Science, University of Kragujevac, Radoja Domanovic ´a 12, 34000 Kragujevac, Serbia e-mail: rankovic@kg.ac.yu S. Sukdolak Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovic ´a 12, 34000 Kragujevac, Serbia 123 World J Microbiol Biotechnol (2008) 24:1239–1242 DOI 10.1007/s11274-007-9580-7