Essential fatty acid components and antioxidant activities of eight Cephalaria species from southwestern Anatolia

Pure and Applied Chemistry, Dec, 2007 by Suheyla Kirmizigul, Nazli Boke, Huseyin Sumbul, R. Suleyman Gokturk, Nazli Arda

Abstract: The hexane extracts of eight Cephalaria (Dipsacaceae) species, which were collected from southwestern Anatolia, were obtained by Soxhlet apparatus. The fatty acids were derived to methyl esters and determined by gas chromatography/flame ionization detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS) systems. The dominant fatty acid components and maximum percentages were detected as myristic [in C. joppica (17.48 %)], palmitic [in C. cilicica, C. elmaliensis, C. isaurica, C. scoparia (19.51 %), and C. gazipashaensis], linoleic [in C. joppica (33.02 %), C. elmaliensis, C. dipsacoides, and C. gazipashaensis], [alpha]-linolenic (ALA) [in C. cilicica, C. elmaliensis, C. isaurica, C. scoparia, C. lycica, and C. gazipashaensis (47.95 %)] and oleic [in C. isaurica and C. dipsacoides (40.66 %)] acids. The antioxidant activity of all hexane extracts was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric thiocyanate (FTC), and thiobarbituric acid (TBA) methods. The results indicate that hexane extracts of Cephalaria species possess considerable antioxidant activity. The highest radical scavenging activity was detected in C. isaurica (I[C.sub.50] = 741 [micro]g/mL). The most effective species on lipid peroxidation are C. lycica and C. gazipashaensis in FTC and TBA assays, respectively. This study reveals that Cephalaria species are attractive sources of fatty acid components, especially the essential ones, as well as of effective natural antioxidants.

Keywords: Dipsacaceae; Cephalaria species; fatty acids; antioxidant activity; radical scavenging; lipid peroxidation.

INTRODUCTION

Cephalaria Schrad. is a genus of about 65 species of flowering plants in the family Dipsacaceae and distributed in the Mediterranean region, the Balkan peninsula, and the Middle East [1]. Cephalaria species have been used in traditional medicine for many years due to their wide range of biological activities [2,3]. According to the literature, they have antimicrobial [4], antifungal [4], antioxidant [5], and cytotoxic [7,8] activities. The chemical constituents of this genus had generally been reported as triterpenoid saponins [9-12], iridoid glycosides [13], flavonoid glycosides [5,6], lignan glycosides [7], hederagenin glycosides [14], and alkaloids [15]. The other two studies on Cephalaria species are determination of fatty acid composition of C. setulifera and C. transsylvanica [16], and the antioxidant activity of C. pastricensis [5]. Another member of the Dipsacaceae family, Dipsacus asper has been investigated for its antioxidant activity [17].

Here, we aim to determine the fatty acid components of hexane extracts by gas chromatography/ flame ionization detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS) techniques and to investigate the antioxidant activities of these extracts by 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric thiocyanate (FTC), and thiobarbituric acid (TBA) methods from eight Cephalaria species (C. joppica, C. cilicica, C. elmaliensis, C. isaurica, C. dipsacoides, C. scoparia, C. lycica, and C. gazipashaensis), six of them are endemic to Turkey, for the first time.

MATERIALS AND METHODS

Plant materials

Plant materials were collected from southwestern Anatolia about 5-2000 m height around Antalya, Turkey in June and July 2006 (Table 1). Voucher specimens were botanically established and deposited in the Herbarium Research and Application Center of Akdeniz University with the numbers R. S. Gokturk 5999, 5998, 5991-A, 5992, 5995, 5996, 6000, and 5991 for C. joppica, C. cilicica, C. elmaliensis, C. isaurica, C. dipsacoides, C. scoparia, C. lycica, and C. gazipashaensis, respectively.

Extraction

Dried and powdered plants were extracted with hexane using a Soxhlet apparatus (70[degrees]C, 6 h) to obtain the fatty acids and the other apolar components. During extraction procedures, Merck hexane (95 %, No. 1.04368) was used. The extracts were concentrated by rotary evaporator under vacuum at ~40[degrees]C. The extraction yields were presented in Table 1.

Methylation of hexane extract

After removing hexane using rotary evaporator, the oily mixtures were derived to their methyl esters by the International Olive Oil Council (IOOC) (2001) and IUPAC (1992) reports by trans-esterification process [18,19]. In this process, dried hexane extracts were dissolved in hexane and then extracted with 2 M methanolic KOH at room temperature for 30 s. The upper phases were analyzed by GC/FID and GC/MS systems [20].

GC/FID and GC/MS analyses

Methyl esters of fatty acids were analyzed using GC-6890 Agilent and MSD (mass selective detector)-5973 Mert Agilent combined system with HP-5 MS apolar column (30 m x 0.25 mm x 0.25 [micro]m). The maximum column temperature, flow of helium, and oven temperature were 350[degrees]C, 0.5 mL/min, and 170-210[degrees]C, respectively. This program was carried out by raising the temperature by 2[degrees]C/min. The fatty acids were identified by comparing their retention times and mass peaks with those of standard methyl ester mixtures and by NIST-Wiley library data search.