THE SEARCH FOR OPTIMALLY BIOACTIVE AUSTRALIAN TEA TREE OIL

I.A. Southwell, A.J. Hayes, J. Markham, D.N. Leach
Antimicrobial activity of tea tree oil was determined using the disc diffusion assay. Terpinen-4-ol, alpha-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.

Southwell, I.A., Hayes, A.J., Markham, J. and Leach, D.N. (1993). THE SEARCH FOR OPTIMALLY BIOACTIVE AUSTRALIAN TEA TREE OIL. Acta Hortic. 344, 256-265
DOI: 10.17660/ActaHortic.1993.344.30
https://doi.org/10.17660/ActaHortic.1993.344.30
Melaleuca, Myrtaceae, essential oil, anti-microbial, zone-of-inhibition, minimum inhibitory concentration
344_30
256-265

Acta Horticulturae