The volatile oils of black pepper [Piper nigrum L. (Piperaceae)], clove [Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae)], geranium [Pelargonium graveolens L'Herit (Geraniaceae)], nutmeg [Myristica fragrans Houtt. (Myristicaceae), oregano [Origanum vulgare ssp. hirtum (Link) Letsw. (Lamiaceae)] and thyme [Thymus vulgaris L. (Lamiaceae)] were assessed for antibacterial activity against 25 different genera of bacteria. These included animal and plant pathogens, food poisoning and spoilage bacteria. The volatile oils exhibited considerable inhibitory effects against all the organisms under test while their major components demonstrated various degrees of growth inhibition.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2000.00969.x

Antimicrobial agents from plants: antibacterial activity of plant volatile oils.

Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. The interest in essential oils and their application in food preservation has been amplified in recent years by an increasingly negative consumer perception of synthetic preservatives. Furthermore, food-borne diseases are a growing public health problem worldwide, calling for more effective preservation strategies. The antibacterial properties of essential oils and their constituents have been documented extensively. Pioneering work has also elucidated the mode of action of a few essential oil constituents, but detailed knowledge about most of the compounds’ mode of action is still lacking. This knowledge is particularly important to predict their effect on different microorganisms, how they interact with food matrix components, and how they work in combination with other antimicrobial compounds. The main obstacle for using essential oil constituents as food preservatives is that they are most often not potent enough as single components, and they cause negative organoleptic effects when added in sufficient amounts to provide an antimicrobial effect. Exploiting synergies between several compounds has been suggested as a solution to this problem. However, little is known about which interactions lead to synergistic, additive, or antagonistic effects. Such knowledge could contribute to design of new and more potent antimicrobial blends, and to understand the interplay between the constituents of crude essential oils. The purpose of this review is to provide an overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents, and to identify research avenues that can facilitate implementation of essential oils as natural preservatives in foods.

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Essential oils in food preservation: mode of action, synergies, and interactions with food matrix components.

Comparative evaluation of 11 essential oils of different origin as functional antioxidants, antiradicals and antimicrobials in foods

Antioxidant activity of selected essential oil components in two lipid model systems

To evaluate the antibacterial activity of 21 plant essential oils against six bacterial species. The selected essential oils were screened against four gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus at four different concentrations (1:1, 1:5, 1:10 and 1:20) using disc diffusion method. The MIC of the active essential oils were tested using two fold agar dilution method at concentrations ranging from 0.2 to 25.6 mg/ml. Out of 21 essential oils tested, 19 oils showed antibacterial activity against one or more strains. Cinnamon, clove, geranium, lemon, lime, orange and rosemary oils exhibited significant inhibitory effect. Cinnamon oil showed promising inhibitory activity even at low concentration, whereas aniseed, eucalyptus and camphor oils were least active against the tested bacteria. In general, B. subtilis was the most susceptible. On the other hand, K. pneumoniae exhibited low degree of sensitivity. Majority of the oils showed antibacterial activity against the tested strains. However Cinnamon, clove and lime oils were found to be inhibiting both gram-positive and gram-negative bacteria. Cinnamon oil can be a good source of antibacterial agents.

/pdf/in-vitro-antibacterial-activity-of-some-plant-essential-oils-115needhff.pdf

In vitro antibacterial activity of some plant essential oils.

The essential oil composition of Cananga odorata, Boswellia thurifera, Cymbopogon citratus, Marjorana hortensis, Ocimum basilicum, Rosmarinus officinalis, Cinnamomum zeylanicum and Citrus limon was analysed by GC and GC–MS, and their antimicrobial and antioxidant activity tested. Twenty-five different genera of bacteria and one fungal species were used in this study as test organisms. These included animal and plant pathogens, food poisoning and spoilage bacteria and the spoilage fungus Aspergillus niger. The volatile oils exhibited considerable inhibitory effect against all the tested organisms. The oils also demonstrated antioxidant capacities, comparable with α-tocopherol and butylated hydroxytoluene (BHT). The method adopted in this study was the modified thiobarbituric acid reactive species (TBARS) assay. The antioxidant activity was carried out under different conditions by using egg yolk and rat liver in the absence and presence of the radical inducer 2,2′-azobis (2-amidinopropane) dihydrochloride (ABAP). © 1998 John Wiley & Sons, Ltd.

Antimicrobial and antioxidant properties of some commercial essential oils

The essential oils obtained from five commercial samples of Sicilian aromatic plants, laurel, sage, oregano, rosemary and coriander were analyzed by GC/MS and assayed for their antibacterial, antifungal and antioxidant activities Twenty-five different genera of bacteria and one fungal species were used in this study as test organisms The oils showed a high degree of inhibition against all the microorganisms tested The highest and broadest activity was shown by the oil of oregano, while the oil of sage was the least effective The antioxidant activity of the oils was measured by the modified Thiobarbituric Acid Reactive Species (TBARS) assay, using egg yolk and rat liver as oxidable substrate, in absence and in presence of the radical inducer 2,2'-azobis (2-amidinopropane) dihydrochloride (ABAP) The activities were compared with those of α-tocopherol and 2,6-di-tert-butyl-4-methylphenol (BHT, butylated hydroxytoluene) The oils showed different effectiveness, the oregano oil being endowed with

Chemical Composition, Antimicrobial and Antioxidative Activity of Laurel, Sage, Rosemary, Oregano and Coriander Essential Oils

The essential oils obtained from Origanum glandulosum Desf., collected in four different localities of the Setif region (north-eastern Algeria), were analysed by GC–MS and assayed for their antioxidative effectiveness. The antioxidant capacity of the oils was measured by the modified thiobarbituric acid reactive species (TBARS) assay, using egg yolk as oxidizable substrate in presence of the radical inducer 2,2′-azobis-(2-amidinopropane) dihydrochloride (ABAP). The activity was compared with those of α-tocopherol and 2,6-di-tertbutyl-4-methyl phenol (BHT, butylated hydroxytoluene). The four oils were also endowed with a high degree of activity at the lowest concentration (100 ppm). This activity is to be ascribed to the high content of phenol components, viz. thymol and carvacrol, which strongly characterize the composition of these oils. Copyright © 2002 John Wiley & Sons, Ltd.

M. Tiziana Baratta

Papers

Antimicrobial and antioxidant properties of some commercial essential oils

Chemical Composition, Antimicrobial and Antioxidative Activity of Laurel, Sage, Rosemary, Oregano and Coriander Essential Oils

Chemical composition and antioxidant activity of essential oils from Algerian Origanum glandulosum Desf.