Antibacterial Properties Of Essential Oils Research Articles

Chemical composition and in vitro antibacterial properties of essential oils of four Thymus species from organic growth

In organic food industry no chemical additives can be used to prevent microbial spoilage. As a consequence, the essential oils (EOs) obtained from aromatic herbs and spices are gaining interest for their potential as preservatives. The EOs of Thymus zygis, Thymus mastichina, Thymus capitatus and Thymus vulgaris obtained from organic growth, were chemically analyzed and identified by GC and GC–MS, while the agar disk diffusion and microdilution assays were used to determine their antibacterial activity. In T. mastichina EO the major compound was 1,8-cineole (51.94%) whilst in T. zygis EO the main constituent was thymol (48.59%). T. capitatus EO was characterized by high content in carvacrol (69.83%). Finally, T. vulgaris EO had a high content of linaool (44.00%).The agar disk diffusion assay, T. zygis and T. capitatus EOs showed inhibitory effects against the ten tested bacteria, while T. matichina and T. vulgaris had inhibitory effects against eight and seven tested bacteria, respectively. T. zygis and T. capitatus EOs had higher inhibition halos against all tested bacteria, at higher concentration (40μL), than T. matichina and T. vulgaris EOs. The microdilution assay, T. mastichina EO had a MIC values ranging between 3.75 and 7.5μL/mL. Whilst in the case of T. zygis, T. capitatus and T. vulgaris EOs the MIC values ranged between 1.87 and 7.5μL/mL.

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

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.

In vitro antibacterial properties of essential oil and organic extracts of Premna integrifolia Linn

The aims of this study were to examine the chemical composition of the essential oil of Premna integrifolia Linn (Lamiaceae), and to test the efficacy of the oil and various organic extracts as an antibacterial potential. The chemical compositions of the essential oil were analyzed by GC–MS. Twenty-nine compounds representing 94.81% of the total leaves oil were identified, of which phytol (27.25%), α-humulene (14.21%), spathulenol (12.12%), 1-octen-3-ol (8.21%), eugenol (6.69%) and phenylethyl alcohol (5.81%) were the major compounds. The oil (15μLdisk−1) and extracts (300μgdisk−1) of P. integrifolia displayed a great potential of antibacterial activity against Sarcina lutea IFO 3232, Bacillus subtilis IFO 3026, Escherichia coli IFO 3007, Pseudomonas sp. ATCC 13867, Klebsiella pneumoniae ATCC 10031 and Xanthomonas campestries IAM 1671 with their respective zones of inhibition of 12.0±1.2 to 22.1±1.2mm and MIC values of 62.5–250μgmL−1. The results of this study suggest that the natural products derived from P. integrifolia may have potential use in food, pharmaceutical and/or agro industries for preservatives or antimicrobial agents.

Antibacterial properties of essential oils and methanol extracts of sweet basil Ocimum basilicum occurring in Bangladesh

The antibacterial potential of essential oils and methanol extracts of sweet basil Ocimum basilicum L. (Lamiaceae) was evaluated for controlling the growth range of food-borne pathogenic bacteria. Essential oils extracted by hydrodistillation from the leaves and stems were analyzed by GC-MS. Fifty-seven compounds representing 94.9 and 96.1% of the total leaf and stem oils, respectively, were identified, of which methyl chavicol (36.7 and 29.9%), gitoxigenin (9.3 and 10.2%), trimethoquinol (10.3 and 8.4%), β-guaiene (3.7 and 4.1%), aciphyllene (3.4 and 3.0%), alizarin (3.2 and 4.4%), naphthaline (2.2 and 3.8%), (–)-caryophyllene (2.0 and 1.9%), and mequinol (1.6 and 1.8%) were the major compounds. The essential oils (10 μL/disc of 1:5, v/v dilution with methanol) and methanol extracts (300 μg/disc) of O. basilicum displayed a great potential of antibacterial activity against Bacillius cereus, B. subtilis, B. megaterium, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Shigella boydii, S. dysenteriae, Vibrio parahaemolyticus, V. mimicus, and Salmonella typhi with their respective zones of inhibition of 11.2–21.1 mm and MIC values of 62.5–500 μg/mL. The results of this study suggest that the natural products derived from O. basilicum may have potential use in the food and/or pharmaceutical industries as antimicrobial agents.

Antibacterial properties of essential oils from Thai medicinal plants

By using disc diffusion assay, the antimicrobial activity of 32 essential oil samples extracted from local plants or plants cultivated in Thailand was evaluated against zoonotic enteropathogens including Salmonella spp., Escherichai coli O157, Campylobacter jejunii and Clostridium perferingens which are important for broiler export. Out of the essential oil tested, only the essential oil of Zingiber cassumuna, Cinnamomum bejolghota, Mentha arvensis var. piperacens, Cymbopogon citratus and Ocimum basilicum var. citratum showed promising antibacterial activity against the bacteria tested.

Antibacterial properties of Thymus pubescens and Thymus serpyllum essential oils

Antibacterial properties of essential oils of Thymus pubescens and Thymus serpyllum collected at pre and flowering stages were studied. The oils were found to possess bactericidal activities.