Artemisia vulgaris L. from Vietnam: Chemical Variability and Composition of the Oil Along the Vegetative Life of the Plant

Journal of Essential Oil Research: JEOR, Jul/Aug 2004 by Thao, Nguyen Thi Phuong, Thuy, Nguyen Thi, Hoi, Tran Minh, Thai, Tran Huy, Et al

Abstract

Essential oils produced from a population of Artemisia vulgaris of Vietnamese origin cultivated near Hanoi were subjected to analysis by GC, GC/MS and ^sup 13^C-NMR. The oils were found to contain oxygenated monoterpenes as major components (1,8-cineole, camphor and [alpha]-terpineol). The composition of these oils differed from that previously reported for Vietnamese A. vulgaris oil. Only slight differences in the composition of the oil were observed along the vegetative life of the plant. No significant difference was observed between compositions of leaf and flower oils. In addition, the combination of retention indices, GC/MS and ^sup 13^C-NMR spectroscopy allowed the identification of unusual sesquiterpenes such as presilphiperfolan-9[alpha]-ol as a minor component.

Key Word Index

Artemisia vulgaris, Asteraceae, essential oil composition, [beta]-pinene, 1,8-cineole, camphor, [alpha]-terpineol, chemical variability, ^sup 13^C-NMR spectroscopy, presilphiperfolan-9[alpha]-ol.

Introduction

The genus Artemisia, which belongs to the Asteraceae family and comprises several species, is widespread in temperate areas (South Europe, North Africa, North America and Asia) (1). Among these species, Artemisia vulgaris L. is a vivace herb, 40-80 cm high, growing wild in Vietnam (2) whose leaves and flowers were used in folk medicine (3). Artemisia vulgaris oil is used for its insecticidal and antimicrobial properties (4-6). The composition of this oil, which exhibits a chemical variability, has been the subject of several studies.

Concerning European oils of A. vulgaris, several compositions dominated by monoterpenes were reported. Italian oils exhibited camphor (47%) alone (7) or camphor (2-20%) associated with myrcene (9-70%), 1,8-cineole (1-27%) orborneol (318%), according to the different origins and the period of harvest (8), as major components. In the leaf oils from France (9), camphor was also present in minor proportions (1-13%) associated with 1,8-cineole (1-23%) and terpinen-4-ol (1-19%). Sabinene (16%), myrcene (14%) and 1,8-cineole (10%) were the major components of an oil from Germany (10).

[alpha]-Thujone (56%) or thujone (unspecified isomer, 35%) associated with camphor (26%) have been identified as the major components of A. vulgaris oils from India (11) and from an unspecified origin (6), respectively. A quite similar composition was reported forthe essential oil from Morocco: thujone/ isothujone (35%) and camphor (30%) were identified accompanied by 21 irregular monoterpenes (12).

Conversely, two oils exhibited sesquiterpenes as major components. The oil of A. vulgaris from Cuba (13) was dominated by caryophyllene oxide (31%), while an original composition, rich in hydrocarbon sesquiterpenes, [beta]caryophyllene (24%), [beta]-cubebene (12%) and [beta]-elemene (6%) was reported for an oil from Vietnam (14).

As part of our ongoing work on the characterization of Vietnamese aromatic plants, we became interested in the chemical composition of A. vulgaris oils. In this paper, we report the composition of oils obtained from a population of A. vulgaris of Vietnamese origin cultivated near Hanoi. We examined the evolution of the composition of the oil along the vegetative life of the plant as well as a comparison between the leaf and flower oils. In fact, the A. vulgaris investigated population produced an oil whose composition, which exhibited monoterpenes as major components, was quite different from that previously reported for a Vietnamese oil (14). In addition, the combination of retention indices, GC/MS and ^sup 13^C-NMR allowed the identification of unusual sesquiterpenes.

Experimental

Plant material and oil isolation: Aerial parts of A. vulgaris were collected during the period September-November 1998 during the vegetative cycle of the herb in different stages: before flowering (A), beginning of the flowering (in bud) (B), flowering stage (C), end of flowering (D). The samples E and F were obtained from flowers and leaves of the same population in flowering stage (October 1998), respectively. Fresh plant material was subjected to hydrodistillation for 4 h using a Clevenger-type apparatus. The oil yields (w/w vs dry material) varied from 0.32-1.14% (see Table I). A voucher specimen has been deposited at the Herbarium of the Institute of Ecology and Biological Resources, Hanoi, Vietnam.

GC and GC/MS analysis: GC analysis was carried out using a Perkin-Elmer Autosystem apparatus equipped with FID and fused-silica capillary columns (50 m � 0.22 mm; film thickness 0.25 �M), BP-I (polydimethylsiloxane) and BP-20 (polyethyleneglycol) as previously reported (15).

GC/MS analysis was performed on a Perkin Elmer Turbo Mass Detector, directly coupled to a Perkin Elmer Autosystem XL equipped with fused-silica capillary columns (50 m � 0.22 mm; film thickness 0.25 �m; polydimethylsiloxane) BP-I and Rtx-Wax (60 m � 0.25 mm; film thickness 0.25 �m; polyethyleneglycol). Injector temperature: 250�C; split: 1/80. Other GC conditions were the same as described under GC. Ion source temperature: 150�C and the detector ionization potential was 70 eV.