In this study, antimicrobial activities of the essential oils obtained by using the hydrodistillation method from some lamiaceous plants--Mentha longifolia (L.) Hudson ssp. longifolia, M. longifolia (L.) Hudson ssp. typhoides (Briq.) Harley var. typhoides, Mentha pulegium L., Salvia fruticosa Miller, Salvia tomentosa Miller, Calamintha nepeta (L.) Savi ssp. glandulosa (Req.) P.W. Ball, Nepeta cadmea Boiss., Lavandula stoechas L. ssp. stoechas, and Ziziphora tenuior L.--were determined by using the disc diffusion method. The plants used in this study were collected from different localities of Muğla Province, Turkey. All the essential oils isolated from the plants were very effective against Gram-positive and Gram-negative bacteria, which included multiple-antibiotic resistant strains, except Pseudomonas aeruginosa ATCC 27853 and Pseudomonas fluorescens MU 87. The essential oils of the plant species, except S. tomentosa and S. fruticosa, were very effective against Candida albicans. The antimicrobial activities varied depending on the species, subspecies, or variety. In fact, essential oils of some plants belonging to the same taxa but collected from different localities showed different levels of antimicrobial activities.

In the present study, four separate samples of Origanum onites L., three separate samples of Satureja thymbra L., Origanum vulgare L. ssp. hirtum (Link) Ietswaart, and Thymus cilicicus Boiss. & Bal. were collected from various regions of Mugla, Turkey. The essential oils of these plants were obtained by the hydrodistillation method. Antimicrobial activities of the essential oils against microorganisms, including multiple antibiotic-resistant bacteria, were investigated using the disc diffusion method. Different antibiotic discs were used for comparison to the inhibition zones. All the essential oils used in this study were very effective against Gram-positive and Gram-negative bacteria, which included multiple resistant strains, except Pseudomonas aeruginosa ATCC 27853 and Pseudomonas fluorescens MU 87. The essential oils of the O. onites, O. vulgare ssp. hirtum, and S. thymbra were especially very effective against the resistant strains such as Stenotrophomonas maltophilia MU 64, S. maltophilia MU 99, and Chryseomonas luteola MU 65. The maximum antimicrobial activity was observed with the essential oils of O. onites. The antimicrobial activities of the essential oils varied depending on the species, subspecies, or variety. In fact, the essential oils of some plants belonging to the same species that were collected from different locations showed different levels of antimicrobial activities.

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The n-hexane, chloroform, ethyl acetate and ethyl alcohol extracts of the aerial parts of Centaurea ensiformis, endemic to Turkey, have been assessed for antimicrobial and antioxidant activities. The chemical composition of the hexane extract of this plant was determined. The antimicrobial activities on microorganisms, including multiple antibiotic resistant bacteria, were evaluated using the disc diffusion method. The antioxidant activities were determined by using four complementary in vitro assays: inhibition of 2,2-diphenyl-1-picrylhydrazyl radical, total antioxidant activity, and the total amount of phenolic and flavonoid compounds. The structure of the active extract was elucidated by: thin layer chromatography, column chromatography, gas chromatography or gas chromatography-mass spectrometry. The various extracts of C. ensiformis inhibited the growth of tested bacteria. All the C. ensiformis extracts had no effect on the yeasts. The total antioxidant activity increased with the increasing amount of the extracts (20, 40, 80 and 160 microg), which contained linoleic acid emulsion. The major compounds of the hexane extract of the plant were caryophyllene oxide (28.72%), spathulenol (17.81%), eudesmol (13.03%) and beta-bourbonene (8.51%).