Complementary and alternative medicines such as tea tree (melaleuca) oil have become increasingly popular in recent decades. This essential oil has been used for almost 100 years in Australia but is now available worldwide both as neat oil and as an active component in an array of products. The primary uses of tea tree oil have historically capitalized on the antiseptic and anti-inflammatory actions of the oil. This review summarizes recent developments in our understanding of the antimicrobial and anti-inflammatory activities of the oil and its components, as well as clinical efficacy. Specific mechanisms of antimicrobial and anti-inflammatory action are reviewed, and the toxicity of the oil is briefly discussed.

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Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties

Antibacterial properties of plant essential oils

Screening methods for natural products with antimicrobial activity: a review of the literature.

The antibacterial activity of 14 essential oils and their major constituents in the gaseous state was evaluated against Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes and Staphylococcus aureus For most essential oils examined, H influenzae was most susceptible, followed by S pneumoniae and S pyogenes, and then S aureus Penicillin-susceptible and -resistant S pneumoniae were comparable in susceptibility Escherichia coli, which was used as a control, showed least susceptibility A minimal inhibitory dose (MID) was introduced as a measure of the vapour activity Among 14 essential oils, cinnamon bark, lemon-grass and thyme oils showed the lowest MID, followed by essential oils containing terpene alcohols as major constituents The essential oils containing terpene ketone, ether and, in particular, hydrocarbon had high MIDs The vapour activity on short exposure was comparable to that following overnight exposure, and rapid evaporation was more effective than slow evaporation of essential oils The vapour concentration and absorption into agar of essential oils reached a maximum 1 or 2 h after rapid evaporation These results indicate that the antibacterial action of essential oils was most effective when at high vapour concentration for a short time

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Antibacterial activity of essential oils and their major constituents against respiratory tract pathogens by gaseous contact

The antimicrobial properties of essential oils (EOs) have been recognised for centuries and, with growing demand from changes in legislation, consumer trends and increasing isolation of antibiotic resistant pathogens, alternatives to chemical-based bactericides need to be found. Citrus oils not only lend themselves to use in food but also are generally recognised as safe (GRAS) and have been found to be inhibitory both in direct oil and vapour form against a range of both Gram-positive and Gram-negative bacteria. This group of oils may provide the natural antimicrobials that the food industry requires to fulfil both its requirements and those of the consumer.

Potential antimicrobial uses of essential oils in food: is citrus the answer?

Vapors of 133 essential oils were screened in vitro for antibacterial activity against six test organisms. One hundred and five vapors were found to possess antibacterial activity on at least one of the test organisms. Vapors of thyme (white), cassia, thyme (red), savory, cinnamon, origanum, and cherry laurel produced prominent zones of inhibition with all test organisms. Gram-positive bacteria were more susceptible to the vapors than Gram-negative bacteria.

Nicholas A. Sicurella

Papers

Antibacterial Activity of Essential Oil Vapors