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The present study was designed to determine the chemical composition of the essential oil from the fiddleheads of Pteridium aquilinum L. Kuhn, so as to enable more effective utilization of such bioactive ingredients. Gas chromatography analysis of the essential oil distillate revealed the presence of 40 compounds that consisted mainly of alkanes (86.60%), monoterpenes (3.20%) and sesquiterpenes (2.40%). The most representative alkanes were tetratriacontane (12.40%), hexatriacontane (8.10%) and heptacosane (8.10%). Predominant monoterpenes were γ-terpinene (0.44%) and 1, 8-cineole (0.40%), and sesquiterpenes were sesquisabinene (0.39%) and β-panasinsene (0.36%). This study when compared with the works of other authors suggested that the essential oil from the fiddleheads of P. aquilinum could play a significant role in perfumery, cosmetic, medicinal, pharmaceutical, and biodiesel industries.


INTRODUCTION
Pteridium aquilinum L. Kuhn (Dennstaedtiaceae) also known as bracken fern, is a cosmopolitan species with world-wide distribution (USDA, 2006).The antibiotic and antibacterial properties of P. aquilinum have been reported (Swain, 1974;Pieroni and Quave, 2005;Hassan et al., 2007), and also its usefulness in the treatment of male fertility and haemorrhoids (Focho et al., 2009).P. aquilinum have been used as source of food world-wide (Pieroni, 2005;Madeja et al., 2009).The fiddleheads are eaten as vegetable by the tribal people of Ogoni in South-South Nigeria, West Africa.
Interest in essential oils has revived in recent times because of their antioxidative, antimicrobial and antiparasitic properties (Toda et al., 1989;Liu et al., 1992;Campbell et al., 1997;Magwa et al., 2006;Tabanca et al., 2007).In view of the wide distribution of P. aquilinum throughout the world, and its medicinal and nutritional applications, there is no study on the chemical composition of the essential oil of the fiddlehead, hence the purpose of this report.

Plant
The fresh fiddleheads of P. aquilinum were collected from Nyogor-Beeri farm area in Khana Local Government Area of Rivers State, South-South Nigeria, and authenticated by Dr. N. L. Edwin-Wosu of the Department of Plant Science and Biotechnology, University of Port Harcourt, Nigeria, where voucher specimen (UPHV-1032) *Corresponding author.E-mail: bin4him@yahoo.com.Tel: +2348037065567.

Extraction of essential oil
The fresh fiddleheads of P. aquilinum were washed, macerated and air dried under shade for 21 days at room temperature until they were crisp, and then pulverised into powder form using electric blender (Bruders BL-133).350 g of powdered sample of dried P. aquilinum fiddleheads were put into a distillation apparatus and mixed with distilled water.The essential oil was extracted by hydrodistillation for about 8 h, using a Clevenger-type apparatus (Clevenger, 1928).The distillate of the oil obtained were dried over anhydrous sodium sulphate and analyzed by gas chromatography.
The essential oil extraction was done in triplicate, and the total amount of essential oil in the powdered sample determined according to the method of Zhang and Liu (2007).

Analysis of the essential oil
The distillate from the steam distillation were then analyzed on a Hewlett-Packard (HP) 6890 gas chromatograph with a wet needle of the sample material being directly inserted into the inlet (spotless mode), and equipped with a Hp1206 software (chemstation Rev. A09.01).The column consisted of a HP-5MS fused silica capillary of 30 m × 0.25 mm × 0.25 m film thickness.The temperature of the oven was programmed from 40 to 200°C at 5°C min -1 , and held isothermally at 200°C for 2 min.The injector temperature was 150°C, and the carrier gas was hydrogen with a flow rate of 1.0 ml/min.Percentage compositions of individual components were obtained from electronic integration using flame ionization detector (FID, 300°C).The volume injected was 0.2 l with a 20:1 split ratio.

RESULTS AND DISCUSSION
Oil yield from dried powdered fiddleheads of P. aquilinum was 0.90% v/w.A total of 40 compounds representing about 60% of the oil from the fiddleheads were obtained from the flame ionization detector.Monoterpenes and sesquiterpenes constituted only 3.20 and 2.40% of the oil, respectively, while the amount of alkane hydrocarbon was 86.60% (Table 1).
The oil was characterised predominantly by alkanes, monoterpenes and sesquiterpenes.There were also benzyl alcohol (0.40%) and n-nonanal (0.30%), present in the oil.

Conclusion
The chemical composition of the essential oil from fiddleheads of P. aquilinum shows that there are several chemicals present in good percentage, which may be very important for industrial purposes, for instance for food, pharmaceuticals, perfumes, cosmetic and biodiesel production.Our results revealed that the fiddleheads of P. aquilinum are rich in essential oil, thus supporting the use of this fern as vegetable and medicinal plant.

Table 1 .
Chemical composition of the essential oil from fiddleheads of P. aquilinum by GC showing their retention time and composition (%).