Octanoic acid

Abstract

The essential oils from aerial parts of five Eryngium species of New South Wales have been examined by GC and GC/MS. The oil of Eryngium expansum F. Muell was characterized by a high amount of 7-epi-[alpha]-selinene (38.3%), cis-[beta]-guaiene (10.8%), 2,3,6-trimethylbenzaldehyde (8.0%) and (E,E)-[alpha]-farnesene (7.3%). The leaf oil of E. pandanifolium Chain, et Schlecht contained bornyl acetate (20.8%), [beta]-selinene (13.8%), [alpha]-selinene (11.3%) and [alpha]muurolene (8.0%) as the main compounds, while the fruit oil was characterized by heptanol (11.5%) and [beta]-selinene (9.2%). The principal compounds of E. rostratum Cav. were found to be spathulenol (20.0%) and [beta]-bisabolol (8.6%) in the leaf oil while [beta]-bisabolol (65.3%) was the main component in the fruit oil. [beta]-Caryophyllene (20.3%), germacrene D (19.2%) and [alpha]-humulene (8.8%) were found to be the major compounds of E. vesiculosum Lab ill. Two populations of an undescribed species (E. sp.1, E. sp. 2) of this genus were also studied, the principal compounds being [alpha]-pinene (14.5-46.2%), bicyclogermacrene (7.1-16.4%), cubebol (0.6-9.0%) and spathulenol (0.8-8.7%). This is the first report on the essential oil composition of these Australian species.

Key Word Index

Eryngium expansum, Eryngium pandanifolium, Eryngium rostratum, Eryngium vesiculosum, Eryngium species, Apiaceae, essential oil composition, [beta]-bisabolol, [alpha]-pinene, 7-epi-[alpha]-selinene, bomyl acetate, [beta]-caryophyllene, spathulenol, germacrene D, bicyclogermacrene, [beta]-selinene, heptanol, [alpha]-selinene, cis-[beta]-guaiene.

Introduction

The Eryngium L. genus belongs to the Apiaceae family and, with about 250 species, is distributed all around the world. In the state of New South Wales (NSW, Australia) there are six cited species, four of them native (E. expansum F. Muell, E. plantagineum F. Muell, E. rostratum Cav. and E. vesiculosum Labill) and the other two naturalized in this Area (E. maritimum L. and E. pandanifolium Cham. et Schlecht) (1).

Although the genus Eryngium appears all around the world, the chemistiy of only a few species has been previously reported. The oligosacharides, sapogenins and derivatives from E. amethystinum L., E. bromeliaefolium Delar, E. giganteum Bied, E. maritimum L. and E. planum L. have been the most studied compounds of this genus (2-6). Falcarinone and derivatives have also been reported from the root extracts of different Eryngium species; E. agavifolium Griseb., E. alpinum L., E. amethystinum L., E. bromelifolium de la Roche, Eryngium bourgatti Gouan, E. campestre L., E. caucasicum Fisch., E. coeruleum LK., E. giganteum H Bieb, E. planum L. and E. serbicum Panc. (7,8).

Eryngium creticum Lam. has been reported as a medicinal plant, and deltione, marmesine, quercitol, 3-[beta]-D-glucopyranosyloxymethyl)-2,4,4-trimethyl-2,5-cyclohexa-dien-.1-one, [beta]-sitosterol, [beta]-sitosterol-[beta]-D-glucopyranose, mannitol and dulcitol were identified from its extracts (9,10). Some of these compounds (D-mannitol and sitosterol) have been successfully tested against snakes and scorpion venoms (11).

Eryngium foetidum L. is a native of South America but it also grows in China, India and Southeast Asian countries. This species has been widely studied as a medicinal plant (12-14) and, besides E. maritimum, it is the only species of this genus from which essential oils have been described. The oil of Eryngium foetidum growing in Vietnam contained (E)-2-dodecanai (45.5%), 2-dodecenoic acid (15.5%), dodecanoic acid (8.6%) and (E)-2-tetradecenaI (5.3%) as principal compounds (15). The leaf and root oils of the same species from Malaysia were characterized by being rich in alkanals and alkenals. The major constituents of the leaf oil were identified as (E)-2-dodecenal (59.7%), 2,3,6-trimethylbenzaldehyde (9.6%), dodecanal (6.7%) and (E)-2-tridecenal (4.6%) while the root oil was characterized by 2,3,6-trimethylbenzaldehyde (37.5%), 2-formyl-1,1,5-trimethylcyclohexa-2,4-dien-6-ol (19.8%), ferulol (9.8%) and 2,3,4-trimethylbenzaldehyde (5.4%) (16). The oil of this species growing in Cuba has been also reported. Thirty-six compounds were identified from the seed oil, the principal ones being carotol (19.3%), (E)-[beta]-farnesene (10%), [alpha]-pinene (7.7%), (E)-anethole (7.4%) and [beta]-bisabolene (6.8%) (17). Forty-six components were identified from the leaf oil and the more important compounds were found to be 2,4,5-trimethylbenzaldehyde (20.5%), hexadecanoic acid (12.05%), carotol (9.9%), (E)-2-dodecenal (5.7%) and methyl (Z,Z)-9,12-hexadecenoate (5.7%) (18).

Although E. maritimum L. is a Mediterranean species, it is widely distributed around the world. The oil composition from different parts of this species has been previously reported. Germacrene D (43.1-42.4%) and 9-muurolen-15-aldehyde (22.4-16.4%), a new sesquiterpene first reported, were found to be the main constituents. The root oil contained [gamma]-guaiene (40.2%), 2,3,4-trimethylbenzaldehyde (24.5%) and germacreiie D (10.6%) as most prominent constituents (19).

In the present work we report on the oil composition of Eryngium species from New South Wales (Australia). This is the first report on the chemistry of these Australian species.

Experimental

Material examined: The aerial parts of five species of Eryngium were gathered in different localities of New South Wales (Australia). A voucher specimen of each sample has been lodged at the N.C.W. Beadle Herbarium of The University of New England [NE] (E. expansum F. Muell NE-075239A, E. vesiculosum Labill. NE-075257A and E. sp. nov. (Basalt Caps) NE-075237A, NE-075250A), at the John T. Waterhouse Herbarium of The University of New South Wales [UNSW] (E. pandanifolium Chain & Schldl UNSW-24482) and at the Gauba Herbarium of The Australian National University [ANUBOZO] (E. rostratum Cav. ANU-037932).

Oil isolation: The oils were isolated from the fresh material by steam distillation with cohobation for 6-8 h as previously described (20) to yield colorless to pale yellow oils. The yields based on wet weight are listed in Table I along with localities, gathered date and voucher numbers oi each sample.

Identification of components: Analytical gas chromatography (GC) was carried out on a Shimadzu GC17A gas Chromatograph with a Megabore column of DB-Wax (60 m x 0.5 mm x 1 µm) which was programmed from 50°-220°C at 3°C/min with helium as carrier gas. GC integrations were performed on a SMAD electronic integrator. GC/MS was performed on a VG Quattro mass spectrometer operating at 70 eV ionization energy. The GC column used was a DB-wax (60 m x 0.32 mm x 0.25 µm) programmed from 35°-220°C at 3°C/min with helium as carrier gas. The oil samples were also analyzed in a Shimadzu GCMS-QP5000 under the same condition but a DB-5 column was used (30 m x 0.25 mm x 0.25 µ). Compounds were identified by their identical GC retention time relative to known compounds and by comparison of their mass spectra with either known compounds or published spectra (20-24).

Results and Discussion

The components identified from the oils of Australian Eryngium species examined in the present work, their retention indices and their percentage composition are summarized in Table II where all the compounds are arranged in order of their elution on the DB-Wax column.

The oil extracted from the aerial parts of E. expansum (E.exp.), was richer on sesquiterpenes than on monoterpeues. The principal compounds were found to be 7-epi-[alpha]-selinene (38.3%), cis-[beta]-guaiene(10.8%),2,3,6-trimethylbenzaldehyde (8.0%) and (E,E)-[alpha]-farnesene (7.3%). Other constituents of the oil were valencene (4.6%), (E)-[beta]-farnesene (3.0%), zingiberene (2.4%) and germacrene D-4-ol (2.2%).

Although E. pandanifolium Cham. et Schlecht is not native to Australia it is naturalized in different parts of NSW. For this reason we have considered it interesting to include it in the present work. The leaf oil from this species (E.panL.) was characterized by a high amount of bornyl acetate (20.8%) although sesquiterpenes were the dominant fraction of the oil. [beta]-Selinene (13.8%), [alpha]-selinene (11.3%) and [gamma]-muurolene (8.0%) were also main compounds of the oil. Other minor constituents of the leaf oil were identified as germacrene D (5.9%), ledol (6.3%), limonene (2.8%) and [alpha]-humulene (2.5%). It is worth mentioning the presence of two oxygenated sesquiterpenes C^sub 15^H^sub 24^O R.I. = 2146 (4.7%) and C^sub 15^H^sub 26^O R.I. = 2263 (3.6%) that could not be identified but their mass spectrum fragmentations are given in Table II. The fruit oil of this species (E.pan Fr.) possessed a similar composition although quantitative differences were detected. The main compounds were octanal (11.5%) and [beta]-selinene (9.2%). The oil also contained low levels of [beta]-elemene (4.4%), octanoic acid (2.5%), ledol (2.3%), trans-pinocarveol (2.3%), caryophyllene oxide (1.6%), [alpha]-selinene (1.4%),2-nonanone (1.4%), nominal (1.4%), heptanal (1.3%) and [gamma]-muurolene (1.0%).

E. rostratum is a grassland species, and it has been previously reported as an efficient recruiter of canopy gaps (26), but its chemical composition has not been previously studied. The stem oil of this species (E.rosS) was richer in sesquiterpenes than the species mentioned above. The principal compounds were identified as spathulenol (20.0%), [beta]-bisabolol (8.6%) and caryophyllene oxide (8.0%). The oil also contained [alpha]-copaene (1.6%), [beta]-elemene (3.9%) and (E,E)-[alpha]-farnesene (1.6%). The oil isolated from the fruits (E.rosFr.) was characterized by a high level of [beta]-bisabolol (65.3%), an oxygenated sesquiterpene, representing more than the 50% of the total oil. Other significant constituents of the oil were [gamma]-terpinene (4.5%), [alpha]-muurolene (3.9%), [alpha]cadinol (2.8%), germacrene D-4-ol (2.6%), [delta]-cadinene (2.4%), bicyclogermancrene(1.9%),T-cadinol (1.3%) and T-muurolol (1.0%).

E. vesiculosum is another native species from Australia and New Zealand. It has been reported to be seasonally heterophyllous, with different leaves during winter and summer seasons (27). The sample examined in the present work (E.ves.) corresponds to the winter leaves (linear and fistular). The oil of this species contained as principal constituents [beta]-caryophyllene (20.3%), germacrene D (19.2%) and [alpha]-humulene (8.8%), all of them sesquiterpene compounds. Other representative components of the oil were found to be [alpha]-pinene (3.7%), [delta]-cadinene (2.7%), (Z)-[beta]-ocimene (2.6%), [beta]-elemene (2.4%), bicyclogermaerene (2.4%), (E,E)-farnesyl acetate (1.8%), [beta]-selinene (1.7%), linalool (1.6%), (E)-[beta]-ocimene (1.2%) and limonene (1.2%).

The oils of other two samples of an undescribed species have also been analyzed to complete this work. This prostrate species appears to be restricted to basaltic soils on the northern tablelands of NSW (L.M. Copeland, pers. obs.). The oils of both samples (E.sp. nov. 1-2) were very similar and they were the only samples studied in this work that contained a monoterpene as the main constituent, [alpha]-pinene (14.5-46.2%). Bicvclogermacrene (7.1-16.4%), cubebol (0.6-9.0%), spathulenol (0.8-8.7%) and [alpha]-cadinol (3.9-7.3%) were also found as principal compounds of the oil. Other minor components identified were [alpha]-cadinol (3.9-7.3%), [gamma]-cadinene (3.0-6.1%), 2,3,6-trimethylbenzaldehyde, (1.3-3.6%) [gamma]-terpinene (0.2-3.3%), T-cadinol (2.3-2.9%) and T-muurolol (1.3-2.5%). The complete list of the components identified is given in Table II. A high amounts of a sesquiterpene hydrocarbon, C^sub 15^H^sub 24^ = 1719 (3.5-12.1%) was detected in the oil of both samples. Although this compound could not be identified in this analysis, its mass spectral data are shown in Table II.

Although all the samples studied belong to the same genus, their chemical compositions are different and they do not necessarily share the principal compounds. But according to our results, practically all the oils of Australian Eryngium species reported here are richer in sesquiterpenes than monoterpene compounds. It is worth mentioning that all the samples were collected during the Australian winter so it could be interesting for future work to compare these results with samples from the flowering period and also to study the chemical composition of the summer leaves of E. vesiculosum.

Acknowledgements

LMC would like to thank Dorothy Bell for field assistance and Ian Telford for taxonomic advice.

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Joseph J. Brophy and Robert J. Goldsack

School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia

Lachlan M. Copeland

Division of Botany, University of New England, Armidale, NSW 2351, Australia

Jesus Pala-Paul*

Dpto. Biologia Vegetal I (Botanica), Facultad de Biologia, Universidad Complutense de Madrid, 28040 Madrid, Spain

* Address for correspondence

1041-2905/03/0006-0392$6.00/0-©2003 Allured Publishing Corp.

Received: August 2001

Revised: November 2001

Accepted: November 2001

Copyright Allured Publishing Corporation Nov/Dec 2003
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