Essential Oil and Fatty Acid Composition of Centaurea solstitialis ssp . solstitialis

Abstract: Centaurea is a widespread genus from Asteraceae family in Turkey. There are plenty of researches about fatty acid and essential oil profiles of Centaurea species. Essential oils were obtained using a Clevenger apparatus by hydrodistillation from aerial part of the plant. The essential oil composition of the plant was identified by GC-MS using FID detector. 31 compounds representing 91.5% were identified. Hexadecanoic acid (50.2%) and tetradecanoic acid(10.1%) were found to be the major compounds. For fatty acids, fatty acid methyl esters (FAMEs) were prepared. The fatty acid compositions were analyzed by GC. Saturated fatty acids (SFAs) were totally 25.05%, monounsaturated fatty acids (MUFAs) were 19.60% and polyunsaturated fatty acids were 19.86%. The major compounds were found as oleic acid (18.54%), linoleic acid (10.07%), palmitic acid (8.28%), stearic acid (6.82%) and γlinoleic acid (6.75%).


INTRODUCTION
Asteraceae family which is included in Cynarae ordo comprises 4 sub-ordo; Carduinea, Carlineae, Centaureinae and Echinipsideae.Centaurea is included in Centaureinae.Asteraceae family has 130 genus in Turkey.Centaurea is a widespread genus including 180 species [1,2].Centaurea genus is widely used in folk medicine as sedative, antipyretic and against allergy in Turkey.Centaurea solstitialis ssp.solstitialis is an also widespread species from this genus.According to the etnobotanic researches, C. solstitalis ssp.solstitialis is mostly used for urinary diseases [3].When we examine the the general content of the species it is well known that sesquiterpene lactones, flavonoids and polyacetylenes are major groups of seconder metabolites [4][5][6].
Fatty acids have many important biological functions such as presenting in biological membran structure and being an energy source.PUFAs and MUFAs are useful for decreasing LDL [7].Essential oils have also different biological activities such as antimicrobial and antioxidant.There are lots of essential oil and fatty acid researches about different Centaurea species [8].
In this study we present the volatile oil profile and fatty acid content of C. solstitialis ssp.solstitalis.To the best of our knowledge, this is the first report for determining essential oil and fatty acid profile of Centaurea solstitialis ssp.solstitialis from Elazığ, Turkey.

Plant Material
C. solstitalis ssp.solstitialis was collected from Elazığ, Turkey in 2011.The plant was identified by one of the authors (B.Kivcak) from Ege University.Voucher specimen was deposited by number 1468 in the Herbarium of Faculty of Pharmacy, Department of Pharmacognosy, Ege University, Izmir, Turkey.The dried and powdered aerial parts of the plant material (40 g) have been extracted by petroleum ether (400 ml) for 6 h at 60ºC by Soxhlet extractor.The solvent was evaporated by a rotary evaporator.The obtained oil was esterified to determine the fatty acid composition.Additionally the air-dried aerial parts of the plant was subjected to hydrodistillation for 3 h using a Clevenger-type apparatus to obtain essential oil.

GC Conditions
Fatty acid methyl esters (FAMEs) were analyzed on a HP (Hewlett Packard) Agilent 6890 N model gas chromatograph (GC), equipped with a flame ionization detector (FID) and fitted to a Supelco SP-2380 Fased Silica capillary column (60 m, 0.25 mm i.d. and 0.2 µm).Injector and detector temperatures were set at 250ºC and 260ºC, respectively.The oven was programmed at an initial temperature of 140ºC and an initial time of 5 min.Thereafter the temperature was increased up to 240°C at a rate of 3°C min -1 .The total run time was 41.33 min.Helium was used as the carrier gas (1 ml min -1 ).Identification of fatty acids was carried out by comparing sample FAME peaks from samples with standarts (26).The results were expressed as FID response area in the relative percentages.Each reported result is given as the average value of three GC analyses.The results are offered as means ±S.D.

Gas Chromatography-mass spectrometry (GC-MS) Conditions
Agilent gas chromatograph model 6890 equipped with an Innowax FSC column (60 m x 0,25 mm x 0,25µm).Instrument conditions were programmed from 60ºC (10 min) to 220ºC (5ºC/min), stayed 10 min at 220ºC and to 240ºC for 1 min.Split ratio was 40:1; injector and detector temperatures were 250 and 280ºC, respectively.The MS conditions were programmed as ionization potential at 70 eV, between 35-450 mass range.In order to identificate the components by comparison, their relative retention times and their relative retention indices (RRI) were used by analyzing Wiley GC/MS Library, Adams Library, MassFinder Library and in Baser Library.Retention indices were determined by using standard alkanes (C9-C30) and also by comparison of literature data.
According to the literature an essential oil research about C. solstitialis from Iran showed different profile than our research about C. solstitialis ssp.solstitialis.In that research hexadecanoic acid was also found to be a major (30.8 %) compound with a different amount and caryophyllene oxide (25.2 %) was also a major compound [10].This difference may be because of the region or the variation of subspecies.Additionally other researches of essential