Leaf Oil of Daniellia ogea L., The

Journal of Essential Oil Research: JEOR, Jul/Aug 2004 by Asekun, Olayinka T, Ekundayo, Olusegun

Abstract

The investigation of the volatile compounds of the leaf oil of Daniellia ogea L. (Leguminosae) by capillary gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) led to the identification of 31 compounds in the oil. The oil was found to be rich in sesquiterpenoids. The major compound was caryophyllene oxide (20.1%). Humulene oxide, [alpha]-humulene and [beta]-selinene were also found in moderate amounts of 6.9%, 3.8% and 3.8%, respectively.

Key Word Index

Daniellia ogea, Leguminosae, essential oil composition, caryophyllene oxide.

Introduction

A number of species of Daniellia yield a balsam or oleoresin that dries to a fragrant resin called 'gum copal' in West Africa (1). The gum resin is used to scent garments or rid them of vermin, and to fumigate huts (2). However, the oleoresin is a yellow or brown viscous liquid with a resinous odor. The plant is reputed to yield a pale yellow volatile oil with a faint aromatic odor.

The chemical literature does not contain any previous report on detailed chemical composition of the leaf oil composition of D. ogea. In 1966, Talalaj distilled and examined the physical and chemical properties of the oil from the 'gum copal' (exudates from wounds) in the trunk of D. ogea and D. oliveri (3). The analyses were incomplete, and an unknown aldehyde was found. Diterpenes, such as daniellic acid, ozoic acid and ozol, were isolated from D. ogea in other previous studies (4-6). The ethanolic extract of the plant was found to possess no antibacterial activity (7). This paper reports for the first time the results of the complete comprehensive analyses of the leaf oil of D. ogea.

Experimental

Plant material: Fresh leaves of D. ogea were collected randomly from 12 plants growing in the experimental plantations of the Forest Research Institute of Nigeria (FRIN), Ibadan. TK. Odewo of FRIN identified the plant and voucher specimens were deposited in the FRIN Herbarium.

Oil isolation: The leaves were air-dried for five days and then finely powdered. The ground plant material was subjected to hydrodistillation in a modified Clevenger-type apparatus (8) to yield a colorless oil (0.05%).

Gas chromatography (GC): GC analysis of the oil was performed on an Orion Micromat 412 gas Chromatograph fitted with a fused silica capillary column (25 m � 0.25 mm) coated with CP-SiI 5 (equivalent to BP-I) (film thickness 0.15 �m); the oven temperature was programmed from 50�-230�C at 3�C/min. The GC detector was a thermal conductor (TCD). The injection and detector temperature were maintained at 200�C and 250�C, respectively. The carrier gas was hydrogen at an inlet pressure of 5 bar. The injection volume of the oil was 0.4 �L. The split ratio was 1:25. The GC was linked to a Merck-Hitachi model 2500 integrator for computing the peak area data.

Gas chromatography/mass spectrometry (GC/MS): GC/MS analysis of the oil was conducted on a Hewlett-Packard HP 5890 A GC coupled to a VG analytical 70-25Os double-focusing MS operating at a voltage of 70 eV electron impact; ion source temperature was 230�C, injector temperature 250�C. The carrier gas was helium. The oven temperature was programmed from 80�-270�C at 10�C/min. The MS spectra were acquired and processed by a VG Digipec Data System equipped with a disc memory.

Component identification: Identification of the constituents of the oil was carried out by comparing the mass spectra data of the compounds with those of authentic standards held in the computer library (data bank) and literature (9). The data in the computer library were obtained from reference samples of other oils of known composition. The comparison of the retention indices of the constituents with those in literature was used to confirm component identification (10).

Results and Discussion

GC and GC/MS analyses of the leaf oil of D. ogea led to the identification of 31 compounds out of 51 compounds in the oil (Table I). The major constituent was caryophyllene oxide (20.1%). Humulene oxide, [alpha]-humulene and [beta]-selinene also occurred in reasonable amounts of 6.9%, 3.8% and 3.8%, respectively.

Limonene (1.7%) was the only monoterpene hydrocarbon in the oil. Four unidentified monoterpene oxides were detected in small quantities (0.2-0.5%). The leaf oil of D. ogea leaves contained mainly sesquiterpenoids, 14 of which were identified.

Only the partial analyses of the oil from the resin of the bark of D. ogea and D. oliveri from Ghana have been reported, and it contained an unidentified aldehyde (6.2-7.6%) (2,11).

Acknowledgements

The technical assistance by O.A. Oyedeji and the financial support from the University oflbadan Senate Research Grants are gratefully acknowledged.

References

1. DJ. Mabberly, The Plant-Book, p 109, 209-289, Cambridge University Press, London (1990).

2. B. Oliver, Nigeria's Useful Plants. The Nigerian Field, 25, 174-192 (1960).

3. S. Talalaj, Essential oil from Danniella Oliverii and D. ogea resins collected in Ghana. West Afrio. Pharm., 8, 90-91 (1966).

4. C.W.L. Bevan, D.E.U. Ekongand J.I.Okogun, West African timbers XVI. Ozoic acid a new diterpene acid from Daniella ogea. Chem. Commun., 44-46(1966).