ISHS Acta Horticulturae 344: International Symposium on Medicinal and Aromatic Plants
THE SEARCH FOR OPTIMALLY BIOACTIVE AUSTRALIAN TEA TREE OIL |
| 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 |
| DOI: | 10.17660/ActaHortic.1993.344.30 |
| Abstract:
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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