Antimicrobial effects of Quercus ilex L. extract

The antimicrobial activities of the methanol extract of Quercus ilex L. (Pırnal oak) leaves were tested in vitro against a wide range of human and plant‐associated microorganisms. A total of 132 microbial organisms belonging to 55 bacteria and ve fungi and yeast species were studied using a disc‐diffusion method and microdilution assays. The results were evaluated as inhibition zones around the disc impregnated with Q. ilex extract at a concentration of 300 µL/mL. The results showed that Q. ilex did not have any antifungal activities against Alterneria alternata , Aspergillus avus , Fusarium oxysporum , Penicillum spp., whereas there were inhibition effects on the growth of all Candida albicans isolates. In total 97 bacterial strains (74%) were found to be resistant to Q. ilex extract. The remaining 35 (27%) strains of seven different bacteria genera including Brucella , Bacillus , Enterobacter , Neisseria , Pseudomonas and Escherichia were susceptible to the extract tested. The minimum inhibitory concentrations (MIC) of the extract ranged from 125 to 500 µL/mL. These results suggest that Q. ilex possesses compounds with antibacterial and anticandidal properties. Copyright © 2004 John Wiley & Sons, Ltd.