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Background: Some plant extracts, including species of Santolina have antibacterial effects and they can be used as antimicrobial agents in treatment of infections. Hence, the aim of this study was to evaluate the compounds of essential oil and the anti-microbial properties of its essential oil and extract. Materials and Methods: In this experimental study, yarrow plant in late spring was collected from Sistan region in 2008. The compounds of the essential oil were analyzed by GC/MS. In this study, the minimum inhibitory concentration (MIC) and diameter of inhibition zone of growth for the standard strains of Staphylococcus aureus, E.coli, P.aeruginosa, and Candida.albicans were determined through disk diffusion and agar-well diffusion methods and dilution in the liquid medium, respectively. Results: Camphor was the major compound of the essential oil. The standard strains of Staphylococcus aureus presented the greatest sensitivity to the stem extract and leaf extract in MIC> 0.573 and MBC> 1.146, respectively and to the flower extract in MBC> 1.663 and MIC> 0.831, respectively. In addition, it presented an intermediate sensitivity to standard strains E.coli with MBC> 2.293 and MIC> 1.146, respectively to the stem and leaf extract and MBC> 6.650 and MIC> 3.325 respectively to the flower extract. However, the standard strains of Candida albicans and P.aeruginosa did not show a significant sensitivity to the extracts. Also, the essential oil of this plant in comparison with the extracts did not have any significant antimicrobial effects. Conclusion: The plant extracts, especially stem and leaf possess anti-bacterial effects. But further investigations are needed for determining its exact mechanism

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Background: Today, with raised use of antibiotics and prevalence of resistant strains, there is need for antimicrobial drugs that have fewer side effects than antibiotics. Rosmarinus officinalis is a medicinal plant which had many uses in traditional medicine. In this study, methanol leave extract of this plant is tested on various pathogens.

Materials and Methods: In this in vitro study, Rosmarinus officinalis was used to evaluate its antimicrobial effects. Methanol leave extract of this plant with concentrations of 400, 200, 100, and 50 mg/ml were prepared, and antibacterial activities were evaluated by well diffusion method on strains of Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus and Staphylococcus aureus. Minimum inhibitory concentration and minimum bactericidal concentration were determined by the microplate method.

Results: In this study, the most efficacy of thanol extract of rosemary leaves was at concentration of 400 mg/ml against Pseudomonas aeruginosa and Escherichia coli. Minimum inhibitory concentration of the extract on the growth of these bacteria showed changes from 6.25 mg/ml to 100 mg/ml. Also MBC  of extract showed range  from 12.5 to 200 mg/ml respectively.

Conclusion: It was found that rosemary methanol extract inhibited growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa but did not inhibit of Bacillus cereus growth.