Essential Oil Composition of Copaifera trapezifolia Hayne Leaves, The

Journal of Essential Oil Research: JEOR, Jul/Aug 2006 by Veiga, Valdir F, Pinto, Angelo C, de Lima, Haroldo C

Abstract

Samples of the leaves of Copaifera trapezifolia Hayne were collected every 3 h over a period of 24 h. Essential oils were isolated from each leaf sample and analyzed by GC and GC/MS. The major constituents were β-caryophyllene (33.5%) and germacrene D (10.9%). No circadian variation was observed.

Key Word Index

Copaifera trapezifolia, Leguminoseae, Copaiba, essential oil composition, β-caryophyllene, germacrene D.

Introduction

The genus Copaifera (Leguminoseae) occurs widely in Latin America, with some species occurring in West Africa (1). Popularly known as Copaiba, the tree exudes an oil from the trunk, the Copaiba oil, long used as a phytotherapeutic drug by indigenous people from Amazonia to Argentina (2). The same oil, according to some authors, can be found in all the plant parts (3). Langenhein studied the relationship between light intensity and leaf resin composition in some species of Hymenaea and Copaifera genera, but obtained no conclusive results with regard to the differences in sesquiterpene composition (4). In this paper, continuing our studies on Copaifera genus, we present the essential oil composition of Copaifera trapezifolia Hayne, a species easily found in the Brazilian Southeast region, but never previously chemically studied, and a 24-h study intended to investigate the circadian variation of the composition of the oil.

Experimental

Plant material and isolation procedure: Leaves were collected every 3 h during a 24-h period between the 21st and 22nd of April 2000, on the eastern external side of a 15 m tree in a latent state without flowers or fruit. Voucher specimens were deposited in the Herbarium of the Rio de Janeiro Botanical Garden (CoL: V.F. Veigajrs.n., April 21" 2000-RB 348.691) and identified as Copaifera trapezifolia Hayne.

The C. trapezifolia tree was located using a Global Positioning System (GPS) at 24° 03' 37.5'' S and 47° 59' 29.2'' W, on the southern side of the Parque Estadual Carlos Botelho, at São Miguel Arcanjo, São Paulo State, in the Southern Region of Brazil.

The plant material collected was immediately cleaned and kept frozen until oil isolation using a microhydrodistillation apparatus. Each microdistillation was performed twice (from each of the eight samples collected), for 10 min with 5.0 g of the leaves and the resulting solution was extracted twice with 1.0 mL of diethyl ether.

Analysis: The oils were analyzed by capillary GC and GC/ M S. The compounds were first tentatively identified by their GC retention indices (determined relative to the retention times of a series of n-alkanes by use of the van der Dool-Kratz equation) obtained on a fused capillary column (25 m long x 0.25 mm x 0.25 µm film thickness, coated with a SE-54 stationary phase, 5% phenyl, 1% vinyl and 94% methyl silicone) and compared with authentic samples of sesquiterpenes from our laboratory. The indices were obtained on a Hewlett-Packard-5890 gas chromatograph with injector and detector temperatures held at 270°C and 300°C, respectively. The oven temperature was programmed from 50°-150°C at 3°C/min followed by 15°C/min rate to 270°C, with high purity hydrogen as the carrier gas. A solution with 1.0 ppm of octadecane was added to the samples as an internal standard.

All the samples were then analyzed by GC/MS, using a capillary GC-quadrupole MS system (Model 5897A) with the same column. The temperature was programmed as follows: 40°C (5 min), 40°-50°C (1°C/min), 50°-150°C (2°C/min), 150°-290°C (15°C/min). Helium was used as the carrier gas at a flow rate of 0.5 mL/min, the mass spectrometer was operated at 70 eV. The identification of the compounds was based on a comparison of retention indices and mass spectra of authentic samples, literature data and computer matching with the Wiley Library.

Results and Discussion

The analyses of the eight different samples collected showed no qualitative or quantitative differences. These data should be confirmed by further examination, during different seasons of the year, as this contrasts Langenhein's experiments that suggested circadian variations of the sesquiterpene composition (4). Leaf alcohols, such as (Z)-3-hexenol, were found in our analysis, showing that micro-hydro-distillation, for only 10 min of distillation time is a good method for obtaining essential oils since as more volatile molecules are readily trapped and analyzed before degradation. The obtained oil composition is shown in Table 1. The sesquiterpenes β-caryophyllene (33.5 %) and germacrene D (10.9%) were the most abundant compounds. More than 95% of the total composition of the oil was identified by retention indices and mass spectrometry data. The added internal standard enabled us to include a mass correspondence between the different compounds, after normalization of the total area. This is the first time that this specie, Copaifera trapezifolia, was studied, and the results obtained are closely related with Langenhein's studies from other Copaifera species.

The presence of coumarin in copaiba seeds was previously related, but not in leaf oil. Limonene, as for any other monoterpene, has not been previously found in Copaifera species, in any tissue. Diterpenes, on the other hand, are extensively found in the literature for Copaiba oil but are not common in leaf oils (2). The presence of kaurene derivatives and other diterpene hydrocarbons, such as m/z 272, can be explained by the Copaiba oil being possibly present in the leaf, as it is expected to be found in all tissues of the Copaiba tree (3).