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The technique of supercritical fluid extraction (SFE) was applied to various sample matrices under a range of supercritical carbon dioxide (scCO2) densities and chamber temperatures. The purpose was to develop an effective extraction condition for the removal of eight target monoterpenes from Australian tea tree (Melaleuca alternifolia Cheel) leaves. The optimum conditions for extraction were found to be 0.25 g/mL scCO2 density at a chamber temperature of 110oC. These condition were most effective when applied to whole fresh and rehydrated whole dried leaves, where it yielded maximum recovery of target analytes with minimum change in oil composition for the extractor system employed. This study demonstrates the importance of the type of sample matrix used in SFE work, and that a different extraction protocol would need to be developed for each matrix.

The effect of mechanical damage on the composition of the essential oil obtained from eugenol-rich Ocimum minimum leaves was determined over 48 hours. Changes in the levels of five oil-constituents were detected in the first post-wounding day but only one of those components (camphor) exhibited the same behaviour the day after. The levels of eugenol (-4.8%) and linalool (+2.5%) were affected the most by the wounding process. Principal component analysis (PCA) showed the post-wounding response to be independent from the pre-wounding levels of the particular compounds expressing the response and from the overall leaf oil-composition.

Research into the mode of action of the essential oil of Melaleuca alternifolia (Tea tree oil) is briefly reviewed. Its mode of action is interpreted in terms of the membrane-toxicity of its monoterpenoid components and different approaches for determining cell membrane damage are discussed.