Bioactive volatiles from 'Geijera parviflora' Lindl. (Rutaceae): evidence for coumarin chemotypes

In the early 20th century, phytochemical studies focused on the leaves of 'Geijera parviflora' to solve the mystery of why grazing herbivores, such as sheep, foraged for some specimens, but not others. After an examination of the essential oils failed to highlight any pattern, phytochemists began examining larger compounds in the leaves and subsequently reported a variety of geographically variable coumarins that could explain this variability in sheep palatability. Today, the investigation continues, but with a view to relate coumarins to traditional medicinal uses employed by Aboriginal Australians. Phytochemical variability related to the sheep palatability of leaves may cast light on the traditional use of 'G. parviflora' for numbing the mouth to treat toothache and for general anaesthesia combating body aches and pains. In this preliminary study, several known and unknown coumarins (together with other chemical groups) have been separated and partially identified from dichloromethane extracts using GC-MS. This method clearly demonstrates a useful protocol for mapping geographical variability of coumarin chemotypes, but is limited to compounds no larger than 328 Daltons.