## 2 Results and Discussion
### Eremophila Deserti  
_Eremophila deserti_ was previously known under the name _Myporum deserti_ and all the past chemical studies of the species were published under this previous name. Consequently, researchers occasionally overlook this, i.e., these details are not included in comprehensive reviews of the genus [11]. Our chemical study of _E. deserti_ reiterated data of the species under its previous name _M. deserti_. Table 3 demonstrates the full chemical diversity of the species. By far the most common metabolite in leaves of _E. deserti_ is methoxymyodesert-3-ene [12], which can vary in some specimens but is typically close to 100% of the gas chromatographic profile (the only component detected), which yields from the leaves at approximately 1-2% g/g of wet leaves. Furthermore, the cluster dendrogram of the chemistry of volatiles from the leaves of _E. deserti_ conveys that the methoxymyodesert-3-ene type represents the most populated branch (Figure 2). In principal component analysis (Figure 3) this chemotype came out as group A. Hence, the methoxymyodesert-3-ene dominated specimens of _E. deserti_ will henceforth be known as the 'type A' chemotype. The details of type A collection locations are provided in Table 2.  
Figure 2: Dendrogram essential oil components from _Eremophila deserti_. Replicate samples of Ede-536 (A-C) and Ede-519 (A-D) (Table 2) were taken from individual specimens within common populations. What this conveys is that even within populations the individual specimens are expressing profiles of volatiles that conform to distinctly separate chemotypes in statistical analysis. Within the population found on the outskirts of Cunnamulla, SW Queensland (specimens Ede-519), one type A specimen was sampled out of four collections made within a 50 m radius. Alternatively, two of the specimens expressed a volatiles profile of >96% pgaione, which came out as type B in the PCA (Figure 3). The ngaione chemotype was previously recognised and published under the old name _M. deserti_[13]. Ngaione was recognised as responsible for the toxicity of the plant to grazing sheep. Ngaione from _Eremophilia_ or _Mypororum_ were previously characterised as the levorotatory enantiomer of (+)-ipomeamarone [14]. A third chemotype was sampled from this location, which corresponds to type C in PCA (Figure 3), comprised by >93% dehydrongaione. Dehydrogenase was also previously recognised [15] for toxic effects to animals. By examination of the other collections made, the type C chemotype expresses variable amounts of dehydrorongaione, in some cases as low as 49.5% of the profile as given by the GC-MS quantitation. One of the specimens (Ede-509B) was sampled twice at different growth stages. During the asexual phase in May (Ede-509B) it expressed methocymyodesert-3-ene and conformed to the type A chemotype, but when the specimen had fruit on it in October (Ede-510) it demonstrated a chemical profile comprised by dehydrorongaione, conforming to the type C chemotype. Hence, it is expected that some specimens will be intermediary between these two chemotypes during the year, i.e., one specimen also expressed >39% methocymyodesert-3-ene in its profile (Ede-471). Furthermore, previous reports of inconsistency of the toxicity of the species may be explained by the changed expression of volatiles during the year. It is not yet clear whether the changes in expression profiles are truly reflective of growth stage or if another factor as yet unrecognised is involved. A fourth chemotype was identified by two specimens that expressed 1-acetylomyodesert-3-ene as the dominant component and myodesert-1-ene, _cis,cis_-repetalactol, and _cis,cis_  
Figure 3: Principal component analysis of essential oil components from _Eremophila deserti_. repetalactone as secondary components. The yield of essential oil of this chemotype was unusually low, i.e., 0.2-0.4%, compared with approximately 1-2% from other chemotypes. Furthermore, the current study constitutes the first report of myodesert-1-ene outside of _E. dalyana_[3].