Antibacterial activity of methanol extract and essential oil of Achillea wilhelmsii against pathogenic bacteria

Background: Increased bacterial resistance to antibacterial agents is one of the most common problems in medicine. Herbal remedies used in the traditional medicine provide an interesting and unexplored source of assessing new drug. The purpose of this study was to determine antibacterial activity of methanol extract and essential oil of aerial part of Achillea wilhelmsii against bacteria.Materials and Methods: Achillea wilhelmsii C-Koch is an endemic plant that has relatively wide distribution in different parts of Iran. The concentrations of 20, 30, 50 and 400 mg/ml of methanol extract were prepared. Antibacterial activities were examined by agar dilution and well diffusion methods against Staphylococcus aureus, Bacillus cereus, E. coli and Pseudomonas aeroginosa. Minimum Inhibitory Concentration (MIC) or Minimum Bactericidal Concentration (MBC) was carried out by tube dilution and well-diffusion methods. Results: Methanol extracts exhibited inhibitory effects on S. aureus, B. cereus and E. coli with a range of MIC values extended from 6.25 to 25 mg/ml. Essential oil at concentration of 1000μg/ml was active against S. aureus , B. cereus and E. coli. They did not have any activity on P. aeroginosa.Conclusion: Methanol extract and essential oil of aerial part of Achillea wilhelmsii inhibited growth of pathogenic bacteria especially gram positive bacteria. Clinical applications of these materials needed further investigations