Mass Spectrometry in the Australian Landscape

In association with gas and liquid chromatography, mass spectrometry has been essential to our understanding of the complex chemical ecology of the Australian bush and plantation forests. This includes the chemical defences of eucalypts against herbivory and fungal decay, and pheromones used for communication between individuals of the same species. Organic chemical classes encountered in this broad chemical ecology network include: • relatively simple (but often novel) aliphatic compounds • terpenes • hydrolysable tannins • condensed tannins • flavonoids • formylated phloroglucinol compounds (FPCs), which have strong antifeedant properties towards marsupials • highly oxidized terpenes formed by metabolic processes in marsupials to detoxify their essential oil rich diet Mass spectrometry has enabled the determination of the structures or partial structures of many new compounds in these classes, as well as being fundamental to the assignment of known compounds. Specific examples, all using negative ion electrospray MS and MS/MS, will relate to eucalypt phenolic chemistry. These include the discovery and assignment of new types of FPCs in eucalypt leaves and wood, the discovery of the mechanism of feeding deterrence to marsupial herbivores conferred by the presence of high levels of FPCs in eucalypt leaves, and detailed investigations into eucalypt tannin chemistry.