Antimicrobial Activity of Several Cineole-Rich Western Australian Eucalyptus Essential Oils

Essential oils from the Western Australian (WA) mallee species , , and subsp. and subsp. were hydrodistilled from the leaves and then analysed by gas chromatography⁻mass spectrometry in addition to a commercial oil and 1,8-cineole. The main component of all oils was 1,8-cineole at 97.32% for subsp. , 96.55% for subsp. , 82.95% for , 78.78% for 2, 77.02% for , and 66.93% for 1. The oils exhibited variable antimicrobial activity determined by broth microdilution, with and oils showing the highest activities. The majority of microorganisms were inhibited or killed at concentrations ranging from 0.25% to 8.0% ( / ). and were the least susceptible organisms, whilst was the most sensitive. In conclusion, all oils from WA species showed microorganism inhibitory activity, although this varied according to both the species and the microorganism tested. These data demonstrate that WA oils show activity against a range of medically important pathogens and therefore have potential as antimicrobial agents.