Three Origanum essential oils, Origanum vulgare ssp. hirtum, Origanum dictamnus, and a commercially available Origanum oil, were analyzed by gas chromatography-mass spectrometry (GC-MS) and showed a high content of carvacrol, thymol, γ-terpinene, and p-cymene representing 73.7%, 92.8%, and 87.78% of the total oil, respectively. The three essential oils exhibited high levels of antimicrobial activity against eight strains of Gram-positive and Gram-negative bacteria. Among the major components of the three oils, carvacrol and thymol exhibited the highest levels of antimicrobial activity, while their biosynthetic precursors γ-terpinene and p-cymene were inactive. The essential oil of O. vulgare ssp. hirtum was extremely bactericidal at 1/4000 dilution and even at dilutions as high as 1/50000 caused considerable decrease in bacterial growth rates. The same essential oil also exhibited high levels of cytotoxicity against four permanent animal cell lines including two derived from human cancers.

The essential oils of Origanum vulgare subsp. hirtum, Mentha spicata, Lavandula angustifolia, and Salvia fruticosa exhibited antifungal properties against the human pathogens Malassezia furfur, Trichophyton rubrum, and Trichosporon beigelii. Of the four oils, O. vulgare subsp. hirtum oil showed the highest fungicidal activity and at a dilution of 1/50000 caused a 95% reduction in the number of metabolically active cells within 6 h of exposure. Among the main components of the four oils, carvacrol and thymol exhibited the highest levels of antifungal activity. The therapeutic efficacy of the O. vulgare subsp. hirtum essential oil was tested in rats experimentally infected with T. rubrum and yielded promising results. Furthermore, the above essential oils were tested with the Ames test and did not exhibit any mutagenic activity.

Salvia fructicosa essential oil analyzed by gas chromatography/mass spectrometry showed high contents of 1,8-cineole, α- and β-thujone, and camphor, representing 47.48%, 11.93%, and 9.04% of the total oil, respectively. The essential oil and its isolated components thujone and 1,8-cineole exhibited antimicrobial activity against eight bacterial strains, while camphor was almost inactive against all of the bacteria tested. The essential oil was bactericidal at 1/4000 dilution, and dilutions up to 1/10000 caused considerable decrease in bacterial growth rates. The essential oil of S. fructicosa and the three main components exhibited cytotoxic activity against African Green Monkey kidney (Vero) cells and high levels of virucidal activity against herpes simplex virus 1, a ubiquitous human virus. Keywords: Salvia fructicosa; essential oil; antimicrobial activity; cytotoxicity; antiviral activity (herpes simplex virus); camphor; 1,8-cineole; thujone

The essential oils obtained from two mint species, Mentha pulegium and Mentha spicata, exhibited antimicrobial properties against eight strains of Gram-positive and Gram-negative bacteria. The essential oils of these mint species at high concentration (1/100 dilution) were extremely bactericidal, whereas lower concentrations (1/1000) caused a dose-dependent decrease in bacterial growth rates. The main p-menthane components of the tested essential oils showed a variable degree of antimicrobial activity not only between different bacterial strains but also between different strains of the same bacteria.

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