Bioactivity and Characterisation of essential oils from 'Geijera parviflora' (Rutaceae) (Lindley) (Wilga bush): a native bush medicine from Australia

Abstract

For ceremonial applications, Aboriginal Australians traditionally baked the leaves of the Wilga bush ('Geijera parviflora'), then ground them to a powder and mixed this with other plant material before smoking to induce a form of intoxication. Medicinally, leaves were also used to numb pain, particularly in suffering a toothache. Essential oils have been extracted and characterized previously, with four main chemotypes identified. Despite this, no effort has previously been made to investigate bioactivities or to relate the chemical composition to the traditional medicinal uses of the oil. In the work presented here, essential oils from many specimens were extracted by hydrodistillation of the leaves and fully characterized in our laboratory using a range of techniques, including TLC bioauthography. The composition of the oils was investigated by GC/MS and compared with the composition of previously published chemotypes. Research here aims to broaden the known traditional applications of the plant and to establish new uses for the essential oil. Antifeedant/larvicidal activity was evaluated; along with antifungal, anti-inflammatory, antimicrobial and free radical scavenging ability. Results indicate that essential oils extracted from the Wilga bush exhibit a range of bioactivities not necessarily related to traditional use. In this regard, further research may help to reveal mechanisms responsible for the local anaesthetic and mind-altering effects described previously.