The Iridoid Myodesert-1-ene and Elemol/Eudesmol are found in Distinct Chemotypes of the Australian Aboriginal Medicinal Plant 'Eremophila dalyana' (Scrophulariaceae)

The strongly aromatic Australian desert species 'Eremophila dalyana' is an Aboriginal medicinal plant that continues to be used today in Central Australia in the treatment of respiratory complaints and 'Sarcoptes scabiei' infestation. Using hydrodistillation of aerial parts of the plant, the new natural product myodesert-1- ene was isolated in two disjunct populations at up to 98% of the volatiles present in the hydrodistilled oils. Weak antimicrobial activities were observed for whole oils and myodesert-1-ene. Activities in the hydrodistilled oil were attributed to the antimicrobial sesquiterpenes elemol and eudesmol which showed good activity when isolated and were relatively abundant in the chemotype used medicinally. The biogenesis of myodesert-1-ene from iridodial is proposed.