In vitro antimicrobial activity of different Verbascum niveum extracts

Introduction. Medicinal plants are the main ingredient of numerous medicines and pharmaceutical products, and antimicrobial activity has been demonstrated in a large number of medicinal plant extracts and essential oils. Considering that Verbascum L. species (mullein), officially approved by the European Medicines Agency, show antimicrobial properties, but also that there are species of this genus that have not been sufficiently studied, the aim of this study was to evaluate the antimicrobial activity of six different extracts of Verbascum niveum Ten. Material and methods. Antimicrobial bioassays were performed with one fungus (Candida albicans) and four bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis) by broth microdilution method according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing. The results were expressed as the minimal inhibitory concentration (MIC) of an extract (mg/ml) that prevents the visible growth of bacteria/fungi. Results. The MIC values ranged from 0.39 to 1.25 mg/ml. The strongest effect was obtained with the ethanolic extract of leaves against Staphylococcus aureus (0.39 mg/ml). Conclusion. Although Verbascum species are considered to be an excellent antimicrobial agent, according to our result, the tested extracts had modest antimicrobial activity.