A Preliminary Investigation of the Leaf Essential Oils of the Australian Species of Endressia, Steganthera and Wilkiea (Monimiaceae)

Abstract

The leaf oils of the 19 Australian species of Endressia, Steganthera and Wilkiea within the family Monimiaceae have been examined by GC and GC/MS. All produced oils in poor yields that were dominated by sesquiterpenes. Endressia wardellii gave a leaf oil in which α-humulene (14–17%) and bicyclogermacrene (17–24%) were the main components. The leaf oil of Steganthera australiana was almost entirely sesquiterpenoid with no one single compound predominating. Steganthera cooperorum, from two disjunct population centers produced different oils indicating significant chemical divergence. In plants from Topaz and Wooroonooran National Park the major components identified were aromadendrene (6–10%), viridiflorene (7–8%), globulol (7–9%) and b-eudesmol (8–11%); dodecanal (2–4%) was also present. However, material from North Mary Logging Area and Daintree National Park produced an oil dominated by elemol (30–42%) and hedycaryol (approx. 8%). These compounds were accompanied by α-, β- and γ-eudesmol (10–14%, 10–14%, 5–9%, respectively). Steganthera hirsuta produced a sesquiterpenoid oil in which the principal components were bicyclogermacrene (37–56%), β-caryophyllene (2–17%) and germacrene D (2–22%). The principal component of Steganthera laxiflora subsp. laxiflora was viridiflorene (13–20%). Steganthera macooraia gave a leaf oil in which the principle sesquiterpenes identified were guaiol (2–23%), bulnesol (0.7–10%) and elemol (10–22%). Steganthera laxiflora subsp. lewisensis gave an oil in which viridiflorene (11.8%) was the principal, with 2-dodecenal (6.3%) also present. The leaf oil of Wilkiea angustifolia was dominated by sesquiterpenes, with β-eudesmol (35%) being the principal component, while in Wilkiea austroqueenslandica the principal components were (E)- β-ocimene (5–9%), germacrene D (7–18%) and bicyclogermacrene (23–26%). Wilkiea cordata gave a variable oil, with either β-eudesmol (22–25%) or spathulenol (11.3%), and several unidentified sesquiterpenes as major components. Wilkiea huegeliana produced an oil in which the main components were α-pinene (10–12%) and viridiflorene (4–9%). Wilkiea longipes gave an oil in which monoterpenes accounted for up to 20% of the oil. In this species, the major monoterpene was (Z)-β-ocimene (11–15%). The remainder of the oil was composed of sesquiterpenes with no one compound predominating. Wilkiea macrophylla was unusual amongst these species in that its oil contained significant amounts of aliphatic aldehydes, in this case dodecanal (2–35%) and (2)-dodecenal (0.1–2%), with β-caryophyllene (14–24%) as the major sesquiterpene. In Wilkiea pubescens the leaf oil was dominated by sesquiterpenes, with no one compound dominating the oil. The aliphatic aldehyde, dodecanal (4–5%) was also present. The leaf oil of Wilkiea rigidifolia contained (Z)-β-ocimene (3.4–11.5%), bicyclogermacrene (3.2–17.4%) and germacrene B (0.3–14.5%) as major components. Wilkiea smithii produced a complicated oil in which β-caryophyllene (10.4%), bicyclogermacrene (9.6%), caryophyllene oxide (8.9%) and spathulenol (16.7%) were the principal components. Wilkiea sp. (McDowall Range J.G.Tracey 14552) yielded a complicated oil that was entirely sesquiterpenoid in nature. The principal components were selina-6-en-4-ol (30.7%) and germacrene D-4-ol (18.6%). Wilkiea sp. (Palmerston B.P.Hyland 80) gave an entirely sesquiterpenoid oil with spathulenol (22%) as the principal component, while Wilkiea sp. (Russell Gorge S.J.Dansie 1909) produced a complicated sesquiterpenic oil with elemol (19.2%) as principal component.