Composition of an Essential Oil from Agonis fragrans J.R. Wheeler et N.G. Marchant

Journal of Essential Oil Research: JEOR, Jul/Aug 2007 by Lowe, Robert F, Russell, Michael F, Southwell, Ian A, Robinson, Christopher J, Day, John

The single-plant extracts showed one plant (6863) devoid of 1,8-cineole which was typical of an isolated provenance which yielded an oil with only 0.6% 1,8-cineole. The decreased 1,8-cineole concentrations were balanced by increased concentrations of á-pinene, linalool and ( )-( IS, 5R)-myrtenol. The identity of the latter alcohol was confirmed following isolation by elution from an alumina column with 10% diethyl ether in hexane. GC retention index (8), mass spectral (8,9), infrared spectral (9) and optical rotation ( 44.6° [86% pure]; lit.(10) 49.7°) data were identical to data from authentic material. This provenance provided the best source (20.0% in the oil, 12 % in the extract) of ( )-(lS, 5R)-myrtenol. This bicyclic monoterpenoid alcohol is used as a flavor and fragrance material and also elicits a response from many insects (11) (eg bark beetle aggregation pheromones (12), vine weevil (Otiorhynchus sulcatus) EAG response (13)). Although common in essential oils, myrtenol does not seem to occur, with the exception ofLippia multiflom (27%) (14), in concentrations greater than 20%.

Other minor variations were evident amongst our sampling. Some provenances (A-C) had little or no á-, â- and ã-eudesmol or their putative precursor cryptomeridiols (6881). Another plant (6864, X) contained lower concentrations of linalool than all other five provenances.

Although it is difficult to distinguish separate chemical varieties amongst the individual and bulk specimens assessed in this investigation, variation is evident. As a potentially commercial fragrance oil, the most abundant populations are those with high 1,8-cineole, á-pinene, linalool and low myrtenol concentrations (6870,6873, 6881,6888; A, B, C, Z). The less abundant low linalool and low cineole/high myrtenol variants also have the potential for commercial development. The latter type seems to have more potential in non-fragrance applications and may find use as a source of myrtenol or as an insect attractant with potential use in lure-and-kill traps for plantation pest control and as a flavoring agent (15). The anti-microbial and anti-inflammatory investigations will be the subject of a separate communication (16).

Acknowledgments

We are grateful to Rural Industries Besearch and Development Corporation for financially supporting this project and to Peter Grayling, Department of Conservation and Land Management, Western Australia for valuable preliminary GC analysis of 55 plants from 11 populations.

References

1. W.R. Elliot and D.L. Jones, Encyclopaedia of Australian Plants Suitable (or Cultivation. VoI 2. pp 242-244, Lothian Publishing Company, Melbourne (1982).

2. J.R. Wheeler, N.G. Marchant and C.J. Robinson, Agonis fragrans (Myrtaceae), a new species from Western Australia. Nuytsla 13,567-570. (2001).

3. I.A. Southwell, C.D.A. Maddox and M.P. Zaluckl, Metabolism of 1. â-c/neoto In tea tree (Melaleuca alternlfolla ancrMelaleuca linariifollaj bypyrgo beetle (Paropsistema tigrls/ J. Chem. Ecol., 21,439-453. (1995).