preliminary examination of the leaf oils of the genus Xanthostemon (Myrtaceae) in Australia

The leaf oils of the Australian species of Xanthostemon have been examined by a combination of GC and GC/MS. Xanthostemon arenarius produced an oil dominated by sesquiterpenes, with the principal components being beta-selinene (12-17%), alpha-selinene (6-10%), 7-epi-alpha-selinene (7-11%), alpha-humulene (0.3-10%, the majority > 6%) and spathulenol (3-19%). Xanthostemon chrysanthus produced a leaf oil in which the principal component was the beta-triketone leptospermone (65-84%). The leaf oil of X. crenulatus was dominated by the sesquiterpene ketone, cyclocolorenone (65-80%) and the aromatic ketone apodophyllone (6-17%). The leaf oil of X. eucalyptoides was dominated by the aromatic ketones baeckeol methyl ether (34-41%), baeckeol (15-29%), isobaeckeol (5-8%) and apodophyllone (7-9%). The leaf oil of X. formosus was, once again, sesquiterpenoid in nature. The principal components were beta-caryophyllene (10-24%), beta-bisabolene (9-16%) and sesquiphellandrene (9-20%). Xanthostemon graniticus was unusual within the genus in that it produced a monoterpenic oil, the principal component being alpha-pinene (69.5%). Xanthostemon oppositifolius gave an oil which was dominated by beta-triketones. The principal components were xanthostemone (16-25%) and a compound considered a one carbon homologue, which is as yet unidentified (24-35%). Xanthostemon paradoxus produced a leaf oil that was sesquiterpenoid in nature. The principal components were beta-caryophyllene (14%), spathulenol (14.9%) and globulol (8%). Xanthostemon psidioides was another species whose oil was dominated by beta-triketones, the principal component being xanthostemone (73.1%). Xanthostemon umbrosus, the species with the widest distribution in this investigation, produced a variable oil. The various oils were dominated by the sesquiterpene ketone, cyclocolorenone (77-83%), or methyl farnesoate (32-57%) and farnesoic acid (9-26%) or alpha-santalene (6-7%), isobaeckeol (30-40%) and an unknown, presumed aromatic, compound mw 252 (3-23%). The leaf oil from X. verticillatus was unusual amongst the other Australian species of Xanthostemon in that it contained 1,3-dimethoxy-5-isopropylbenzene as its major component (96-97%). Xanthostemon whitei gave a sesquiterpenic oil which was similar to that produced by X. arenarius. Xanthostemon youngii also gave a sesquiterpenic oil, the principal components being alpha-copaene (3-13%), beta-caryophyllene (11-13%), aromadendrene (3-12%), and delta-cadinene (4-18%)