Chemical composition and antimicrobial effects of the essential oil of Thymus pubescens Boiss. & Kotschy ex Celak from different localities

This research was aimed to investigate the effect of collection locality and essential oil concentration of Thymus pubescens Boiss. & Kotschy ex Celak on antimicrobial activity against some microorganisms. The statistical design used in this study was a factorial experiment in a completely randomized design with four replications. In this experiment, collection locality at six levels including the habitats of West Azarbaijan, Tehran, Zanjan, Qazvin, Kurdistan and Guilan, essential oil dilution at three levels including one fifth (1:5), one twenty-fifth (1:25), one fiftieth (1:50) and comparison with the antibiotics of ciprofloxacin and ceftizoxime, and studied microorganisms at five levels including Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeroginosa and Candida albicans were investigated. The seeds were collected from different habitats and cultivated in the field of Research Institute of Forests and Rangelands. The essential oil was isolated from shoots by hydro-distillation. Chemical compositions of the oils were analyzed by GC and GC/MS. The essential oil yield obtained from different localities varied between 0.39% to 0.83% (w/w). The major constituents of the essential oil obtained from the samples collected from West Azarbaijan, Tehran, Zanjan, Qazvin, Kurdistan and Guilan were as follows: West Azarbaijan: E-caryophyllene (26.0%) and camphor (24.2%); Tehran: geranial (30.9%) and geranyl acetate (23.9%); Zanjan: linalool (23.5%) and 1,8-cineol (22.2%); Qazvin: thymol (30.3%) and carvacrol (30.1%); Kurdistan: linalool (17.2%) and geranyl acetate (12.7%), and Guilan: α–terpineol (31.2%) and geraniol (11.2%). Analysis of variance of inhibition zone diameter of T. pubescence essential oil showed significant difference (p<0.05) among collection locality, microorganism type, essential oil dilution and their interaction. Mean comparisons of the collection locality, microorganism type and essential oil dilution showed that the highest inhibition zone diameter (35.5mm) was recorded for the essential oil obtained from West Azarbaijan, ciprofloxacin against Bacillus subtilis. The lowest inhibition zone diameter (8.0 mm) was observed in the essential oil obtained from West Azerbaijan with essential oil dilution of 1:50 against P. aeruginosa. According to the MIC and MBC results, the most and the least antimicrobial activity was recorded for the essential oils obtained from the seeds collected from Tehran and Kurdistan, respectively.