Essential Oil of Phyllanthus reticulatus Poiret from Nigeria *

The chemical composition of the essential oil obtained by hydrodistillation from the leaves of Phyllanthus reticulatus Poiret (Euphorbiaceae) growing in Nigeria has been studied. The constituents of the oil were analyzed by means of gas chromatography (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). Monoterpenes (64.9%) were the dominant class of compounds, followed by sesquiterpenes (23.0%). The major constituents were α-pinene (6.0%), sabinene (7.6%), β-pinene (18.1%), linalool (6.9%) and camphor (7.7%), among the monoterpenes, and β-caryophyllene (11.9%) and germacrene D (8.6%) among the sesquiterpenes. This is the first report on the volatile constituents of Phyllanthus reticulatus.


Introduction
Phyllanthus reticulatus Poiret., (Family Euphorbiaceae) is a many branched deciduous shrub or small tree sometimes partially scrambling, usually 1 -5 m high.P. reticulatus usually has a distinct smell that is emitted by the minute flowers when they open towards the early evening.The bark is light reddish-brown or grey-brown with hairy stems when young, which become smooth with age.The leaves alternate along slender branches.They are up to 25 cm long and appear as leaflets of large pinnate leaves.The leaves are thinly textured, usually hairless.It flowers from September to October, but the flowering season can extend from July onwards.P. reticulatus has very small, roundish berry like fruits that are green at first, turning purple-black, 4 -6 mm in diameter [1].Extracts of the plant is known to possess both analgesic and anti-inflammatory activities [2]- [4].Aqueous extract of P. reticulatus can be utilized for prevention of atherosclerosis in hypercholesterolemic patients [5].There are reports which describe the antiviral [6], antibacterial [7], hepatoprotective 8], antioxidant [9], potential RNase H inhibition and protection against the viral cytopathic effects of HIV-1 [10], antidiabetic [11] and hypoglycemic [12] activities.
The objective of the present work was to examine the volatile constituents of this plant for future exploration.Our finding into the volatile oils of some poorly studied Nigerian flora was recently published [21].

Plant Sample
Leaves of P. reticulatus were collected from a location in Ibefun, Odogbolu, Ogun State, Nigeria, on March, 2012.Botanical identification was performed by Messrs Ugbogu O.A and Shasanya, O.S., at the Herbarium Headquarters, Forestry Research Institute of Nigeria (FRIN), Ibadan, Nigeria, where voucher specimen (FHI 109586) has been deposited for future reference.

Extraction of Essential Oil
Aliquots (400 g) of the air-dried and pulverized plant sample were subjected to hydrodistillation for 3 h using a Clevenger-type apparatus in accordance with the British Pharmacopoeia specification [22] to produce a pale yellow essential oil.

Analysis of the Oil
GC analysis was accomplished with a HP-5890 Series II instrument equipped with a HPWax and HP-5 capillary columns (both 30 m × 60 for 10 min, rising at 5 /min to 220 .The injector and detector temperatures were maintained at 250 ; ative proportions of the oil constituents were percentages obtained by FID peak-area normalization without the use of response factor. GC-EIMS analysis was performed with a Varian CP-3800 gas-chromatograph equipped with a HP-5 capillary column (30 m × conditions: injector and transfer line temperature 220 and 240 respectively; oven temperature programmed from 60 -240 at 3 /min; carrier gas was helium at a flow rate of 1 mL/min 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/sec.

Identification of the Constituents
Identification of the constituents was based on comparison of the retention times with those of authentic samples, comparing their linear retention indices (LRI) relative to the series of n-hydrocarbons, and on computer matching against commercially available spectral [23]- [25].Further identifications were also made possible by the use of homemade library mass spectra built up from pure substances and components of known oils and MS literature data.Moreover, the molecular weights of all the identified substances were confirmed by GC-CIMS, using MeOH as CI ionizing gas.

Conclusion
The chemical constituents of essential oil obtained from P. reticulatus grown in Nigeria are being reported for the first time.In addition, a comparison of the chemical composition was made with the other known essential oils from Phyllanthus plants.It could be seen that the essential oils of Phyllanthus plants exhibit high chemical variability.Each species has its own compositional pattern different from other.The very high content of compounds identified in the oil of P. reticulatus may be an important chemical and economic characteristic of the oil sample.
a Elution order on HP-5MS column; b Retention time in order with respect to the chromatogram (Figure1); c Retention indices on HP-5 MS capillary column; d Literature retention indices (References 23 -25); Tr, Trace amounts < 0.1%.