Summary

Existing international standards (e.g. ISO 4730, British and European Pharmacopoeias) define the composition of tea tree oil from Melaleuca alternifolia in terms of bulk attributes of the oil (e.g. colour, density and refractive index), and the presence of a limited number of chemical components. A literature review of the chemical composition of tea tree oil (de Groot and Schmidt, 2016 Contact Dermatitis) found over 220 different chemicals reportedly identified in tea tree oil, although about half of these components were determined from a single study, and the authenticity or age of the samples tested was rarely conclusively demonstrated. However, common adulterants such as eucalyptus or pine oil contain similar terpene compounds, and deliberate adulteration may not be easily identified. 

Plants often produce metabolites as chiral molecules, and enantiomers can differ from one species to another within the same genus. Essential oils often contain chiral compounds in specific ratios, making these compounds good markers of adulteration. As a consequence, the chiral ratios of specific terpenes have also been proposed as potential indicators of tea tree oil quality (Davies et al. 2016 J. Agric. Food Chem.).

Here we propose to use both GC-MS screening and chiral analysis of key terpenes for the characterisation of a library of authentic and known provenance M. alternifolia samples, to better understand the unique composition of Australian tea tree oil and ensure authenticity can be verified into the future.

 

Program

Tea Tree Oil

Research Organisation

Chemistry Centre (WA)