Antimicrobial Activity of Aqueous-Alcoholic Extracts and the Essential Oil of Verbascum thapsus L.

The increasing resistance of human pathogens to the available antimicrobials is a serious threat, resulting in the need for novel antibiotic resources such as plants. Some species of the genus Verbascum have been used by mankind since ancient times as an effective remedy for infectious diseases. This study was designed to determine the antimicrobial efficacy of the aqueous-alcoholic extracts and the essential oil of Verbascum thapsus L. against different kinds of bacterial and fungal strains, viz. Streptococcus pyogenes, Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus fumigatus. The antimicrobial activities of the V. thapsus extracts were examined in the present study on the basis of disc diffusion and microdilution assays, and their potency was quantitatively assessed in terms of inhibition zone diameters and minimum inhibitory concentration (MIC) values. The disk diffusion test showed that the methanol extract of V. thapsus had more growth inhibitory effects on E. coli and S. pyogenes than the aqueous and ethanol extracts. The methanol and aqueous extracts had no effects on S. aureus. The maximal inhibition zone for the microorganisms sensitive to the methanol extract was in the range of 7 - 16.8 mm, and the MIC value was 31.25 ?g/mL. For the ethanol extract, the maximal inhibition zone was 5.3 - 11 mm and the MIC value was 62.5 - 125 ?g/mL. The essential oil of V. thapsus did not exhibit any antibacterial and antifungal activities. The findings of the present study revealed the V. thapsus extract possesses compounds with antibacterial properties that can be used as novel antimicrobial agents in the development of new drugs for the treatment of infectious diseases