Leaf Essential Oils of Lycopus australis (Lamiaceae), the Australian Gipsywort

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

Abstract

The leaf essential oil of Lycopus australis contained β-phellandrene (26-40%), β-caryophyllene (7-16%) and α-humulene (18-30%) as principal components. The oil yield was 0.1-0.4% w/w based on fresh foliage.

Key Word Index

Lycopus australis, Lamiaceae, essential oil composition, β-phellandrene, β-caryophyllene, α-humulene.

Introduction

The genus Lycopus comprises appoximately 15 species, with 14 occurring in temperate parts of Europe, and a single species, L. australis R.Br., in Australia (1,2). One species, L. europaeus L. (Gipsywort), has roots that contain a dye that has been used to stain faces brown in the past (3). Several species of Lycopus are or have been used in Western and Asian medicines (4). We are not aware of L. australis being exploited in any way by indigenous Australians. The essential oils of L. lucidus, which contained a range of mono- and sesquiterpene constituents, including β-caryophyllene and a-humulene (5,6), L. uniflorus, which contained mainly monoterpenes, including β-phellandrene (7) and L. europaeus, which contained a range of oxygenated and hydrocarbon monoterpenes (8), have been examined. Lycopus australis has not been examined in any way by chemists.

The Australian species, L. australis is sporadically distributed in eastern Australia with a northern limit near Jimna in southeast Queensland, through New South Wales to Victoria and South Australia. It is an erect wiry herb growing to about 1 m high with minute white flowers, and invariably is found in swampy areas or along watercourses. The crushed foliage has a pleasant, slightly aromatic odor.

Experimental

Plant material: Plant material was obtained from three individual plants, PIF28077: Queen Mary Falls National Park, 7 km E of Killarney, Qld, 28° 20' S, 152° 02' E. A voucher specimen has been deposited in the Queensland Herbarium (BRI).

Isolation of oils: The leaf oils were isolated by hydrodistillation with cohobation as previously outlined (9). Analyses of the oils were carried out by gas chromatography and combined gas chromatography/mass spectrometry.

Identification of components: Analytical gas chromatography (GC) was carried out on a Shimadzu GC17 gas chromatograph. A WCOT DB-Wax [60 m x 0.5 mm, film thickness 1 µm] was used, programmed from 50°-225°C at 3°C/min with helium at 3.5 mL/min as carrier gas. GC integrations were performed on a SMAD electronic integrator. GC/MS was performed on both a VG Quattro mass spectrometer operating at 70 eV ionization energy, the column used was DB-Wax [60 m x 0.32 mm, film thickness 0.25 µm] programmed from 35°-220°C at 3°C/min, with helium at 35 cm/min as carriergas and a Shimadzu QP5000 instrument equipped with a DB-5 column [30 m x 0.25 mm, film thickness 0.25 µm]. The column was programmed from 35°-250°C at 5°C/min, helium carrier gas flowrate was 30 cm/s. Compounds were identified by their identical GC retention times to known compounds and by comparison of their mass spectra with either known compounds or published spectra (10-14).

Results and Discussion

The steam distilled leaf oil of Lycopus australis was dominated by the monoterpene β-phellandrene (26-40%) and the sesquiterpenes β-caryophyllene (7-16%) and α-humulene (18-30%). These were accompanied by lesser amounts of myrcene (2-4%), germacrene D (2-4%), caryophyllene oxide (1-2%), (E)-nerolidol (2-3%) and humulene epoxide II (4-5%). Oxygenated derivatives of both β-caryophyllene and α-humulene appeared also to be present in small mounts (1-2%). They were also present in small amounts in the extract of the leaf. The complete analysis is given in Table I. The oil yield was 0.1-0.4% w/w, based on fresh foliage.

In contrast to L. uniflora oil, which was mainly composed of monoterpenes (7), that of L. australis contained large amounts of both mono- andsesquiterpenes, though in common with L. uniflora, both species contained significant amounts of β-phellandrene.

Acknowledgements

Thanks are due to G. Leiperfor assistance in the collection of this plant, and A.R. Bean for details of its location.

References

1. B.J. Conn, Lamiaceae. In: Flora of New South Wales. Edit., G.J. Harden, 3, 623-664, University of New South Wales Press, Kensington (1992).

2. B.J. Conn, Lamiaceae. In: Flora of Victoria. Edits., N.G. Walsh and T.J. Entwisle, 4, 418-459, lnkata Press, Melbourne (1999).

3. B.M. Lawrence, Chemical constituents of Labiatae oils and their exploitation. In: Advances in Labiatae Science. Edits., R.M. Harley and T. Reynolds, 399-436, Royal Botanic Gardens, Kew (1992).

4. D. Brown, Encyclopaedia of Herbs and their Uses. RD Press, Sydney (1995), p 307.

5. Shuping Man and Yuxin Feng, Pharmacogosy and essential oil analysis of zetan. Zhongguo Yaoxue Zazhi, 27, 648-650 (1992); Chem. Abs., 118, 209423 (1993).

6. Soon Hee Shin, Youn Sim, You Sun Kim, Hyung Joon Chi and Eun Bang Lee, Studies on essential oils of Lycopus lucidus Jurez. Saengyak Hakhoechi, 23, 29-33 (1992); Chem. Abs., 117, 137497 (1992).

7. B.M. Lawrence, J.W. Hogg, S.J. Terhune, J.K. Mortonand L.S. Gill, Terpenoid composition of some Canadian Labiatae. Phytochemistry, 11, 2636-2639 (1972).