Leaf Oils of Coatesia and Geijera (Rutaceae) from Australia, The

Journal of Essential Oil Research: JEOR, Mar/Apr 2005 by Brophy, Joseph J, Goldsack, Robert J, Forster, Paul I

Abstract

The leaf oils of the Australian members of the genera Geijera and Coatesia have been examined by GC and GC/MS. Coatesia paniculata gave a consistent oil in which the principal components were α-pinene (27-57%) and β-caryophyllene (4-12%). Geijera linearifolia gave a leaf oil dominated by spathulenol (10-17%), geranyl acetate (4-9%), bicyclogermacrene (3-6%) and (E,E)-farnesol (23-30%). Four chemotypes of Geijera parviflora were detected: (1) in which geijerene/pregeijerene and linalool predominated, (2) in which linalool and α-and β-eudesmol predominated, (3) in which α-pinene and camphene predominated and (4) in which phloroacetophenone dimethyl ether predominated. Geijera salicifolia also existed in several chemotypes, one of which contained large amounts of phloroacetophenone dimethyl ether (> 65%). Also present in this particular chemorype was the geijerene/pregeijerene and attendant C^sub 12^H^sub 18^ complex, totaling approximately 5%. In a second sample of this chemotype, this complex was absent. A second chemotype of this species contained α-pinene (38.6%), camphene (22.4%) and limonene (7.5%) as principal components.

Key Word Index

Coatesia paniculata, Geijera linearifolia, Geijera parviflora, Geijera salicifolia, Rutaceae, essential oil composition, α-pinene, camphene, linalool, geijerene, pregeijerene, β-caryophyllene, spathulenol, α-eudesmol, β-eudesmol, (E,E)-farnesol, dimethylphloracetophenone.

Introduction

The genus Geijera Schott is considered to comprise about five species (1), although erroneous figures of eight species have sometimes been mentioned (2). Three species are native to Australia, with one species (G. salicifolia Schott) also found in New Guinea (3) and New Caledonia (1). Two other species (G. balansae Schintz et Guillaumin and G. cauliflora Baill.) are endemic to New Caledonia (T.G.Hartley, pers. comm. 2002). Until recently, the species known as G. paniculata (F.Muell.) Druce (syn. G. helmsiae F.M.Bailey) was also referred to as Geijera, however, Hartley (1) has recently resurrected the monotypic genus Coatesia F.Muell. for this species.

All the species of Coatesia and Geijera are large shrubs or small trees. Hartley (1) defined Coatesia as having unarmed foliage, alternate simple leaves, bisexual flowers, the fruit dehiscent and with an endocarp that is elastically discharged with the seed, the testa thin, brittle and lustrous, and endosperm lacking. By comparison he defined Geijera as having unarmed foliage, alternate simple leaves, bisexual flowers, the fruit dehiscent and with an endocarp that (together with the seed) is not discharged, the seeds with a thick testa, shiny pellicle, and a copious endosperm. In his synoptical key to Rutaceous genera, he placed Coatesia and Geijera adjacent to Zanthoxylum, but species of that genus have usually aculeate (spiny) foliage, leaves that are iinparipinnate, paripinnate orthree-foliolate and flowers that are unisexual. All three of these genera are currently classified in the subfamily Rutoideae, tribe Zanthoxyleae, and are probably allied to other genera occurring in Australia such as Bosistoa F.Muell. ex Benth., Bronibya F.Muell., Bouchardatia Baill., Dinospenna T.G.Hartley, Euodia J.R.Forst. et G.Forst., Halfordia F.Muell., Lunasia Blanco, Medicosma Hook.f., Melicope J.R.Forst. et G.Forst., Pentaceras Hook.f. and Pitaviaster T.G. Hartley. In this current paper we examine the leaf essential oils of the Australian species of Geijera and the Australian endemic Coatesia paniculata.

Coatesia paniculata (axebreaker, capivi, scrub wilga) is endemic to subcoastal eastern Australia where it occurs from near Townsville in the north to Wardell in north-eastern New South Wales in the south. This species forms a shrub or small tree between 2-8 m in height and grows in dry rainforest (araucarian microphyll vineforest, semi-evergreen vinethicket) on a variety of substrates (often talus) derived from andesite, basalt, chert, sandstone and serpentinite.

Geijera linearifolia (DC.) J.Black (oilbush or sheepbush) is endemic to subcoastal south Australia (2) and adjacent parts of Western Australia (4). It is a shrub or small tree up to 4 m tall and grows on the edges of salt lakes or on limestone substrates.

Geijera parviflora Lind. (wilga, tree wilga, lavender bush) is endemic to eastern mainland Australia and widespread in Queensland (northern limit north-east of Mt Coolon, 21° 18'S) and New South Wales, with a southern limit near Nenley in north-western Victoria (5). It is usually found in woodland of brigalow (Acacia harjwphylla), or mixed woodland of eucalypts (e.g. Eucalyptus populnea), mulga (Acacia aneura), cypress pine (Callitris glaucophylla) or belah (Casuarina cristata). Geijera parviflora invariably forms a shrub or small tree up to 7 m high, always with a distinct weeping foliage. The crushed foliage generally has a very distinctive scent ('wilga smell') although can be more prevalent at different times of the year. The foliage is often eaten by domestic stock during drought conditions. According to Everist (6), two distinct forms exist of G. parviflora in terms of edibility to domestic stock (e.g. sheep). One of these (tree wilga) occurs in drier areas (with less than 500 mm per annum) and is readily browsed. The other (lavender bush) occurs in wetter areas (with more than 500 mm per annum) and is not browsed. Wilga is also considered of value as a source of pollen and nectar in honey production (7).

Geijera salicifolia (syn. G. latifolia Lindl., G. muelleri Benth.) (greenheart, green satinheart, scrub wilga) is widespread in eastern Australia from the Mcllwraith Range in the far north of Queensland to Jerry's Plains (32° 35'S) in New South Wales in the south. This species is also found in the northern parts of Western Australia and the Northern Territory, parts of eastern New Guinea (Morobe and Central provinces of Papua New Guinea) and New Caledonia. In Australia it is an extremely variable species, particularly in terms of leaf morphology, but with no apparent discontinuities between the different forms. Plants may grow in dry rainforest (littoral microphyll vineforest, semi-evergreen vinethicket, semideciduous notophyll vineforest) or open eucalypt dominated woodland, on a wide range of substrates derived from basalt, granite, limestone, pegmatite or serpentinite. It fonns a shrub or small tree up to 16 m in height. Hartley (1) considered that this was the most primitive species of Geijera, presumably based on its relict distribution. As with G. parviflora, the foliage may be eaten by domestic stock during droughts (6). The timber is suitable for use as fishing rods, interiors or cabinet work (8).