Chemical compositions of Casuarina equisetifolia L., Eucalyptus toreliana L. and Ficus elastica Roxb. ex Hornem cultivated in Nigeria

Essential oils were obtained by separate hydrodistillation of three different plants cultivated in Nigeria and analysed comprehensively for their constituents by means of gas chromatography (GC) and gas chromatography-mass spectrometry (GC – MS). The leaf essential oil of Casuarina equisetifolia L. (Casuarinaceae) comprised mainly of pentadecanal (32.0%) and 1,8-cineole (13.1%), with significant amounts of apiole (7.2%), α -phellandrene (7.0%) and α -terpinene (6.9%), while the fruit oil was dominated by caryophyllene-oxide (11.7%), trans -linalool oxide (11.5%), 1,8-cineole (9.7%), α -terpineol (8.8%) and α -pinene (8.5%). On the other hand, 1,8-cineole (39.4%) and α -terpinyl acetate (10.7%) occurred in large quantities in the essential oils of the leaf of Eucalyptus toreliana L. (Myrtaceae). The oil also features high levels of sabinene (5.9%), caryophyllene-oxide (4.7%) and α -pinene (4.2%). The main compounds identified in the leaf oil of Ficus elastica Roxb. ex Hornem. (Moraceae) were 6,10,14-trimethyl-2-pentadecanone (25.9%), geranyl acetone (9.9%), heneicosene (8.4%) and 1,8-cineole (8.2%). film thickness 0.25 μ m) and a Varian Saturn 2000 ion trap mass detector. Analytical conditions: injector and transfer line temperature 220 °C and 240 °C, respectively; oven temperature programmed from 60 to 240 °C, at 3 °C/min.; carrier gas was helium at a flow rate of 1 mL/min.; injection of 0.2 μ L (10% hexane solution); split ratio 1:30. Mass spectra were recorded at 70 eV. The acquisition mass range was 30 – 300 m/z at a scan rate of 1 scan/s.


Introduction
Casuarina is a genus of 17 species in the family Casuarinaceae, native to Australasia, southeastern Asia, and islands of the western Pacific Ocean. Casuarina equisetifolia L. is a widespread seashore tree known as Common Ironwood, Beefwood, Bull-oak, and Whistling-pine and is often planted as a windbreak. This species is not a pine at all, but superficially resembles a conifer (Pinyopusarerk and House, 1993). The plant is a source of biologically active compounds such as catechin, ellagic acid, gallic acid, quercetin and lupeol, which are antioxidants (Aher et al., 2009), coumaroyl triterpenes (Takahashi et al., 1999) and d-gallocatechin (casuarin) (Nash et al., 1994). The plant is also known to store tannins (Li-Hua et al., 2009) and proline (Tani and Sasakawa, 2003) as well as being a nitrogen fixing plant (Li-Hua et al., 2009). C. equisetifolia also displays antimicrobial properties (Parekh et al., 2005).
Eucalyptus (Myrtaceae) is a large genus of trees and shrubs, which originates mainly from Australia. Eucalyptus torreliana L., is one of the known 500 species of Eucalyptus that produces terpenoids. The leaves of the Eucalyptus species have medicinal and flavouring properties. The essential oil-bearing Eucalyptus plants rank high both in quantity and frequency among the plants that are widely used all over the world (Ogunwande, 2001). Reports on the chemical constituents of some Eucalyptus species cultivated in Nigeria have been published (Ogunwande et al., 2003;Ogunwande et al., 2005;Jimoh et al., 2005).
Ficus elastica Roxb. ex Hornem, (also known as the rubber tree) is a common house plant, as it can grow in moderately luminous environments. As with other members of the genus Ficus, the flowers require a particular species of fig wasp to pollinate it in a co-evolved relationship. Rubber plants are not known to produce highly colourful or fragrant flowers to attract other pollinators (Busari, 2001

Isolation of the volatile oils
Aliquots of air-dried and pulverised samples were hydrodistilled in an all glass Clevenger-type apparatus for 3 h according to established procedure (British Pharmacopoeia, 1990). Aliquots of leaves (1.0 kg) and fruits (0.40 kg) of C. equisetifolia afforded pale yellow oils at yields of 0.09 and 0.10% (v/w), respectively. In addition, 0.45 and 0.95 kg of E. torreliana and F. elastica afforded colourless and pale yellow oils, respectively, at yields of 0.34 and 0.11% (v/w).

Gas chromatography (GC) and gas chromatographymass spectrometry (GC-MS)
GC analysis was accomplished with an HP-5890 Series II instrument equipped with HP-Wax and HP-5 capillary columns (both 30 m × 0.25 mm, 0.25 μm film thickness), with the following temperature programme: 60°C for 10 min, rising at 5°C/min to 220°C. Both injector and detector temperatures were maintained at 250°C; carrier gas nitrogen (2 mL/min); detector, FID; split ratio 1:30. The volume injected was 0.5 μL. The identification of the components was performed by comparison of their retention times with those of pure authentic samples and by means of their linear retention indices (LRI on HP-5 column) relative to the series of n-hydrocarbons. The relative proportions of the oil constituents were percentages obtained (% area) by FID peak-area normalisation without the use of response factor.
Gas chromatography-electron ionisation mass spectrometry analysis was performed with a Varian CP-3800 gas-chromatograph equipped with a HP-5 capillary column (30 m × 0.25 mm; Table 1 Constituents of the leaves and fruits of Casuarina equisetifolia.

Constituents LRI Percentage
Leaves Fruits ; split ratio 1:30. Mass spectra were recorded at 70 eV. The acquisition mass range was 30-300 m/z at a scan rate of 1 scan/s. Identification of the constituents was based on comparison of the retention times with those of authentic samples, comparing their linear indices relative to the series of n-hydrocarbons, and on computer matching against commercially available spectral (Adams, 2005). Further identifications were also made possible by the use of self constructed spectral library built up from pure substances and components of known oils and MS literature data (Davies, 1990;Jennings and Shibamoto, 1980;Massada, 1975). Moreover, the molecular weights of all the identified substances were confirmed by gas chromatography-chemical ionisation mass spectrometry, using methanol as CI ionising gas. Table 1 lists the compounds identified in the leaf and fruit oils of C. equisetifolia. Seventy-six compounds comprising of monoterpene hydrocarbons (29.3%), oxygenated monoterpenoids (16.2%), sesquiterpene hydrocarbons (2.7%), oxygenated derivatives (1.0%), aliphatic (40.6%) and non-terpenoid (7.2%) compounds were observed in the leaf oils. The major compounds were pentadecanal (32.0%) and 1,8-cineole (13.1%). Significant quantities of α-phellandrene (7.0%), apiole (7.2%) and α-terpinene (6.9%) were present. The fruit oil was devoid of sesquiterpene hydrocarbon compounds. The main constituents were caryophyllene-oxide (11.7%), translinalool oxide (11.5%), 1,8-cineole (9.7%), α-terpineol (8.8%) and α-pinene (8.5%). All the eleven compounds identified in the oil occurred at levels between 3.4 and 11.7%. Both caryophyllene-oxide and trans-linalool oxide were absent in the leaf oil. The authors are not aware of any literature report on the constituents of the essential oil of the plant or of any Casuarina species and as such the present study may represent the first of its kind.