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

Biological and Phytochemical Screening of Plants

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

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.

Antibacterial Activity of Essential Oil Vapors

One hundred perfume oils were tested for antimicrobial properties against a series of pathogenic and nonpathogenic bacteria and fungi. The in vitro filter paper disk method was used exclusively for testing activity. The perfume oils were found to possess remarkable antimicrobial properties with greater activity against fungi than against bacteria. It is suggested that perfume oils be incorporated more widely into common toilet articles applied to the body surfaces as well as medicaments used externally.

The Antimicrobial Activity of Perfume Oils

The in vitro antifungal activity of 92 volatile oils, 12 terpeneless oils, and 3 fixed oils was ascertained using the filter paper disk method. The oils were tested against 18 pathogenic and nonpathogenic fungi. Ninety volatile oils were found to possess antifungal activity on at least one organism. Origanum (red), lemongrass (imported), thyme (red), sweet birch, savory select, coriander, sassafras, cinnamon, laurel leaves (distilled), and chenopodium exhibited the greatest antifungal activity. Streptomyces venezuelae was most susceptible to the volatile oils while Candida krusei was the most resistant. Among the terpeneless oils, cinnamon, caraway, dill, and anise were found to possess the greatest antifungal activity. The fixed oils used were found to possess no antifungal properties. Oils of chenopodium, origanum (red), and dill (terpeneless) were found to be very effective against Ustilago avenae ; chenopodium and thyme (red) against Trichophyton mentagrophytes ; and oil of cinnamon against Epidermophyton interdigitale . More than 90% of the volatile and terpeneless oils tested were found to produce fungicidal effects.

The In Vitro Antifungal Activity of Essential Oils

The in vitro antibacterial activity of thirty-five volatile oils, five fixed oils, five infused oils, and ninety-five combinations of these oils was ascertained using the filter paper disk method. The oils and oil combinations were tested against five bacteria. Eucalyptus, cinnamon, and origanum red exhibited the greatest antibacterial activity while the volatile oils of cedar wood and myrrh as well as all of the fixed and infused oils were found to possess no activity. The Gram-positive bacteria were more susceptibleto the volatile oils than the Gram-negative. Of the ninety-six combinations of oils only three were found to exhibit greater antibacterial activity as compared with each oil used separately. The three combinations of volatile oils which showed this enhancement of antibacterial activity were: eucalyptus-cinnamondwarf pine needle, eucalyptus-cinnamon-juniper berries, and eucalyptus-cinnamonniaouli. When fixed or infused oils were added to volatile oils the antibacterial activity of the latter was markedly diminished.

Jasper C. Maruzzella

Papers

Antibacterial Activity of Essential Oil Vapors

The Antimicrobial Activity of Perfume Oils

The In Vitro Antifungal Activity of Essential Oils

The In Vitro Antibacterial Activity of Essential Oils and Oil Combinations

Effects of Vapors of Aromatic Chemicals on Fungi