Chemical Constituents of the Essential Oil of Laggera pterodonta ( DC . ) Sch . Bip . From North-Central Nigeria

The aerial part of Laggera pterodonta plant found in North-Central part of Nigeria was hydrodistilled and the volatile oil subjected to GCMS analysis. 23 components were identified in the essential oil of which n-Triacontane was the major constituent (~43%). Other major volatile constituents include, Dimethoxydurene (~9%), Caryophyllene oxide (~7%), Linoleoyl chloride (~7%), oleic acid (~4%), gamma-Eudesmol (~4%), 2,6,10-trimethylundeca-1,3,diene (~3%) and n-Dotriacontane (~3%). This is the first time that n-triacontane is being found as the major constituent of an essential oil, and also the first time the composition of the essential oil of Laggera pterodonta from North-central Nigeria is being reported.


INTRODUCTION
Laggera pterodonta is annual shrub found growing as common weed in Nigeria.It belongs to the family Asteraceae (Compositae) and the genus consists of about 20 species.The plant is spread throughout the sub-Saharan Africa and the tropical countries of Asia, especially Southeast Asia, in open waste spaces and partially shaded galleried forest.It grows in Senegal, Sierra Leone, Nigeria and West Cameroons, and probably occurring elsewhere in the region (Burkill, 1985;Wu et al., 2011).Reports of chemical constituents of the volatile oil from the species in Benin and Cameroon as well as other regions showed variation in composition (Egharevba et al., 2010;Asfaw et al., 2001;Asfaw et al., 1999).The essential oil from the plant had been reported for use as an insecticide in Cameroon (Njan Nlôga et al., 2007;Ngamo et al., 2007).Despite the huge potential of the plant and its essential oil, it remained highly under-studied in Nigeria.The aim of this study was to examine the chemical constituents of the essential oil of the Nigerian species of the plant from North-central part of Nigeria with a view to establish the chemotype and usefulness.

MATERIALS AND METHODS
All the solvents and reagents used in the study were of Analar grade and, unless otherwise stated, were sourced from Zayo-Sigma, Abuja, Nigeria.

Collection and Extraction of Plant Material
The plant (aerial part) was collected on the 15 November, 2009 from Chaza village, Suleja, Niger State, North-central zone of Nigeria, and authenticated by the Taxonomist in the Department of Medicinal Plant Research and Traditional Medicine of the National Institute for Pharmaceutical Research and Development (NIPRD) Abuja, Nigeria.The plant was assigned a voucher specimen number NIPRD/H/6403.The roots were removed and the fresh aerial parts were rinsed in distilled water and immediately used for the study.

Hydrodistillation
500g of fresh material was chopped to size with a clean kitchen knife and hydrodistilled over 5hrs using Clevenger apparatus.The oil/water mixture was collected into a glass sample bottle.The mixture was salted with 3g of sodium chloride salt and then extracted with hexane.The moisture in the hexane extract was removed with 2g of anhydrous sodium sulphate and filtered.The hexane filtrate was collected in a glass bottle and subjected to GCMS analysis.

GCMS Analysis
The oil was analysed on a Shimadzu GCMS-QP2010 Plus (Japan) at the National Research Institute for Chemical Technology (NARICT) Zaria, Nigeria.The column length, diameter and thickness were 30m, 0.25mm and 0.25µm respectively, and the stationary phase was 100% dimethylpolysiloxane.The conditions for analysis were set as follows; column oven temperature was programmed from 60-280°C (temperature at 60°C was held for 5min, raised to 140°C at 5°C/min and then finally to 280°C at 15°C/min and held for 10min); injection mode, Split (1.0); injection temperature, 250°C; flow control mode, linear velocity (46.3cm/sec); pressure, 100.2 kPa; carrier gas, helium; total flow rate, 6.2mL/min; column flow rate, 1.61 mL/min; ion source temperature, 200°C; interface temperature, 250°C; solvent cut time, 2.50 min; start time 3.00 min; end time, 35.00 min; start m/z, 40 and end m/z, 400.

RESULTS AND DISCUSSION
Table 1 shows the GCMS data and the identified constituents of the hydrodistilled essential oil.The identification of the constituents was based on comparison of their mass spectra data with those available in the data bank of NIST library.The oil extraction yield was 0.001% v/w.