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Abstract
In recent years there has been an increasing interest in the use of natural substances,
and some questions concerning the safety of synthetic compounds have encouraged more
detailed studies of plant resources. Essential oils, odorous and volatile products
of plant secondary metabolism, have a wide application in folk medicine, food flavouring
and preservation as well as in fragrance industries. The antimicrobial properties
of essential oils have been known for many centuries. In recent years (1987-2001),
a large number of essential oils and their constituents have been investigated for
their antimicrobial properties against some bacteria and fungi in more than 500 reports.
This paper reviews the classical methods commonly used for the evaluation of essential
oils antibacterial and antifungal activities. The agar diffusion method (paper disc
and well) and the dilution method (agar and liquid broth) as well as turbidimetric
and impedimetric monitoring of microorganism growth in the presence of tested essential
oils are described. Factors influencing the in vitro antimicrobial activity of essential
oils and the mechanisms of essential oils action on microorganisms are reported. This
paper gives an overview on the susceptibility of human and food-borne bacteria and
fungi towards different essential oils and their constituents. Essential oils of spices
and herbs (thyme, origanum, mint, cinnamon, salvia and clove) were found to possess
the strongest antimicrobial properties among many tested.