Joseph J Brophy* and Robert J Goldsack, Lachlan M Copeland and Paul I Forster

Abstract: The leaf oils of the species of Philotheca growing in Queensland and northern New South Wales have been examined by combined GC and GC/MS. Philotheca cuticularis, both subspecies of P. difformis, P. glasshousiensis, P. myoporoides subsp. myoporoides, P. epilosa, P. obovata, P. queenslandica and P. sporadica all produced leaf oils in which the major component (>75%) was α−pinene. In P. acrolopha, the major components were α−pinene (34–42%) and β−caryophyllene (12–22%), while in P. ciliata the principal components were α−pinene (48–54%) and camphor (18–25%). In P. ericifolia the major components were α−pinene (16–25%), myrcene (7–10%), (E)−β−ocimene (18–34%) and the sesquiterpene spathulenol (13–21%). Pilotheca conduplicata produced a monoterpenic oil in which the main components were α−pinene (27.2%), limonene (43.8%) and (E)−β−ocimene (18.3%). In Philotheca papillata α−pinene (43.0%), camphene (9.3%) and elemol (8.8%) were the principal components of the leaf oil. The leaf oil of P. salsolifolia subsp. salsolifolia contained α−pinene (31.9%) and spathulenol (18.1%) as its major components, while in P. salsolifolia subsp. pedicellata sabinene (38%) and bicyclogermacrene (15.2%) were the major components.

The genus <i>Philotheca</i> Rudge comprises small shrubs that have aromatic foliage and is endemic to Australia with 51 species currently recognized (1–3). Over half the species occur in southern Australia, with the remainder in eastern Australia and south-western Western Australia. <i>Philotheca</i> was allied by Wilson to the genera <i>Crowea</i> Sm. and <i>Eriostemon</i> Sm. from Australia and the species currently known as <i>Eriostemon pallidus</i> Schltr. (an undescribed genus) from New Caledonia (1). All of these genera belong to the tribe Boronieae and are distinguished by morphological characters such as the petal aestivation, form of the seed testa and chalazal opening, cotyledon shape and staminal form (1). All species of <i>Philotheca</i> have aromatic foliage characterized by conspicuous oil glands; however, little work has been published on essential oil compositions. In the current paper we describe the essential oils found in the foliage of the <i>Philotheca</i> species from Queensland and northern New South Wales. Brief notes are given below on each species and subspecies arranged within the sectional classification of Wilson (1) wherein four sections were recognized. Only taxa from the sections <i>Philotheca</i> and <i>Erionema</i> occur within the geographical area outlined above.