Thyme and Peppermint Studied for Antimicrobial and Antioxidant Actions
Recent studies are examining essential oils as means to preserve food without the use of synthetic chemicals. The two important features of essential oil activity is that they act both as antimicrobials, preventing the growth of unwanted micro-organisms, and as anti-oxidants, preserving 'freshness'. (These actions take place not only in petri dishes, but within humans as well). Here are a couple of studies examining Thyme and Peppermint essential oils and their actions:
Chemical composition of essential oils of Thymus and Mentha species and their antifungal activities.
Sokovi? MD, Vukojevi? J, Marin PD, Brki? DD, Vajs V, van Griensven LJ.Institute for Biological Research "Sinisa Stankovi?", Bulevar despota Stefana 142, 11000 Belgrade, Serbia.
The potential antifungal effects of Thymus vulgaris L. (Thyme essential oil), Thymus tosevii L., Mentha spicata L. (Spearmint essential oil), and Mentha piperita L. (Peppermint essential oil) and their components against 17 micromycetal food poisoning, plant, animal and human pathogens are presented. The essential oils were obtained by hydrodestillation of dried plant material. Their composition was determined by GC-MS. Identification of individual constituents was made by comparison with analytical standards, and by computer matching mass spectral data with those of the Wiley/NBS Library of Mass Spectra. MIC's and MFC's of the oils and their components were determined by dilution assays. Thymol (48.9%) and p-cymene (19.0%) were the main components of T. vulgaris, while carvacrol (12.8%), a-terpinyl acetate (12.3%), cis-myrtanol (11.2%) and thymol (10.4%) were dominant in T. tosevii. Both Thymus species showed very strong antifungal activities. In M. piperita oil menthol (37.4%), menthyl acetate (17.4%) and menthone (12.7%) were the main components, whereas those of M. spicata oil were carvone (69.5%) and menthone (21.9%). Mentha sp. showed strong antifungal activities, however lower than Thymus sp. The commercial fungicide, bifonazole, used as a control, had much lower antifungal activity than the oils and components investigated. It is concluded that essential oils of Thymus and Mentha species possess great antifungal potential and could be used as natural preservatives and fungicides.
Study: Antimicrobial and antioxidant activities of three Mentha species essential oils.
Mimica-Duki? N, Bozin B, Sokovi? M, Mihajlovi? B, Matavulj M.University of Novi Sad, Faculty of Natural Sciences and Mathematics, Department of Chemistry, Novi Sad, FR Yugoslavia.
The present study describes the antimicrobial activity and free radical scavenging capacity (RSC) of essential oils from Mentha aquatica L., Mentha longifolia L., and Mentha piperita L. (Peppermint essential oil). The chemical profile of each essential oil was determined by GC-MS and TLC. All essential oils exhibited very strong antibacterial activity, in particularly against Esherichia coli strains. The most powerful was M. piperita essential oil, especially towards multiresistant strain of Shigella sonei and Micrococcus flavus ATTC 10,240. All tested oils showed significant fungistatic and fungicidal activity [expressed as minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) values, respectively], that were considerably higher than those of the commercial fungicide bifonazole. The essential oils of M. piperita and M. longifolia were found to be more active than the essential oil of M. aquatica. Especially low MIC (4 microL/mL) and MFC (4 microL/mL) were found with M. piperita oil against Trichophyton tonsurans and Candida albicans (both 8 microL/mL). The RSC was evaluated by measuring the scavenging activity of the essential oils on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and OH radicals. All examined essential oils were able to reduce DPPH radicals into the neutral DPPH-H form, and this activity was dose-dependent. However, only the M. piperita oil reduced DPPH to 50 % (IC50 = 2.53 microg/mL). The M. piperita essential oil also exhibited the highest OH radical scavenging activity, reducing OH radical generation in the Fenton reaction by 24 % (pure oil). According to GC-MS and TLC (dot-blot techniques), the most powerful scavenging compounds were monoterpene ketones (menthone and isomenthone) in the essential oils of M. longifolia and M. piperita and 1,8-cineole in the oil of M. aquatica.
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