Volatile constituents of Euphrasia stricta

Abstract

The genus Euphrasia is fairly large with 450 species distributed in both the hemispheres in Europe, Asia, Northern parts of America, mountains of Indonesia to New Zealand, and South America [1]. The Serbian flora recognizes eight species of Euphrasia genus [2]. Euphrasia stricta J. P. Wolff ex J. F. Lehm. (eyebright) has been a part of the traditional folk medicine for centuries and is used for the treatment of various eye problems such as cataracts, conjunctivitis, and red, inflamed, irritated, and sore eyes [3–5]. The literature data on its constituents and their action is limited. The principal compounds in the aerial part are iridoids, phenolic acids, and phenylpropane, and flavonoid glycosides [6–8]. To the best of our knowledge, there is no report found in the literature on the chemical composition of Euphrasia stricta volatile constituents. Aerial parts of Euphrasia stricta were collected during the flowering period, in August 2011, from natural populations of Bojana s Waters, Suva Planina Mountain, Serbia. A voucher specimen, with the accession number 16517, is deposited at the Herbarium of the Department of Botany, Faculty of Biology, University of Belgrade – Herbarium Code BEOU. Oil was obtained from air-dried aerial parts of the plant in 0.02% (w/w) yield by hydrodistillation for 4 h using a Clevenger-type apparatus. The oil analyses were performed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) systems. The GC analysis of the oil was carried out on an HP-5890 II gas chromatograph equipped with a split-splitless injector on an HP-5MS capillary column (30 m 0.25 mm, 0.25 m film thickness) with helium as the carrier gas (1 mL/min) and flame ionization detector (FID). Operating conditions: injector temperature 250 C and interface temperature 280 C, temperature program from 50 C (3 min) to 250 C at a rate of 3 C/min. GC/MS analyses were performed on an Agilent Technologies apparatus, Model GS 6890N, at 70 eV coupled with a mass selective detector MSD 5975C under the same gas-chromatograph conditions. The identification of compounds was based on a comparison of Kovats retention indexes using AMDIS software (ver. 2.64) in combination with a chemometric multivariate resolution method and selective ion analysis (SIA) [9]. The identity of the compounds was confirmed by comparing their data with those from the literature [10], and their mass spectra with the Wiley 275 and NIST/NBS libraries. Relative retention indexes (RRI) were obtained by co-injection a C9–C28 standard mixture of aliphatic hydrocarbons. The results of GC and GC/MS analyses of the investigated oil are summarized in Table 1. Forty-seven compounds were identified, representing 84.0% of the total oil. Fatty acids and their derivatives were found in large quantities. Palmitic acid was detected as the major component, constituting 20.3% of the oil. Other significant compounds were -palmitolactone (11.4%), ethyl linolate (7.6%), 9,12,15-octadecatrien-1-ol, (Z,Z,Z) (6.1%) and phytol (5.2%), while other constituents were in less than 5%.