|Authors: ||I.A. Southwell, A.J. Hayes, J. Markham, D.N. Leach|
|Keywords: ||Melaleuca, Myrtaceae, essential oil, anti-microbial, zone-of-inhibition, minimum inhibitory concentration|
Antimicrobial activity of tea tree oil was determined using the disc diffusion assay.
Terpinen-4-ol, -terpineol and 1,8-cineole were found to have greater mobility through agar than hydrocarbon congeners in agar plate zone-of-inhibition measurements.
Minimum inhibitory concentrations were measured using an agar plate dilution method where a range of oil concentrations in agar were tested against S. aureus, E. coli, P. aeruginosa, C. albicans and A. niger.
This method was used to show that concentrations of 1,8-cineole in excess of the upper limit specified in the Australian Standard are not inhibitory.
At concentrations up to 30% cineole appears to be synergistic.
Antimicrobial activity decreased only when terpinen-4-ol levels fell below 30%, the minimum limit specified in the standard.
Preliminary results also indicated that (+) and (-)-terpinen-4-ol are equally bioactive.
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