The essential-oil composition of Telekia speciosa (Schreb.) Baumg. from Trabzon-Turkey

Abstract

Previously, the essential oil from the aerial parts of Telekia speciosa (Schreb.) Baumg. (Asteraceae) from Serbia was reported to have a complex composition with (E,Z)-farnesol, (E)-nerolidol, β-caryophyllene, caryophyllene oxide, intermedeol, and alantolactone as the main components [1]. The plant material analyzed in the current study was collected in July 2017 from Maçka-Trabzon with an aim to identify the chemical constituents of T. speciosa essential oil from Turkey (for the first time) and compare it with the reported oil from Serbia. The essential oil was obtained from air-dried aerial parts of the plant by hydrodistillation (3 h) using a Clevenger apparatus in a yield of 0.06% (v/w). The essential oil was diluted 1:10 (v/v) with n-hexane and used as such for the GC-MS analysis. The essential oil was analyzed with an Agilent 5977 MSD GC-MS system operating in EI mode; injector and MS transfer line temperatures were set at 250 °C. Splitless injection was used in the analysis. Innowax FSC column (60 m x 0.25 mm, 0.25 µm film thickness) and helium as the carrier gas (1 mL/min) were used in GC-MS analyses. The oven temperature program was: 60 °C for 10 min and then raised to 220 °C at a rate of 4 °C/min, afterwards the temperature was kept constant at 220 °C for 10 min and then raised to 240 °C at a rate of
1 °C/min. Mass spectra were recorded at 70 eV with the mass range m/z 35-425. Relative amounts of the separated compounds were calculated from the integration of the peaks in MS chromatograms. Identification of essential-oil components was carried out by comparison of their retention indices (RI), relative to a series of n-alkanes (C₅ to C₃₀), with the literature values, as well as by mass spectral comparison. One hundred thirty-four compounds were identified representing 80.5% of the detected oil constituents. The main components of the oil were caryophyllene oxide (8.2%), β-caryophyllene (6.0%), precocene II (3.9%), isoalantolactone (3.5%), trans-phytol (2.9%), nerol (2.9%), hexadecenoic acid (2.6%), neryl propionate (2.5%), and thymohydroquinone dimethyl ether (2.3%). The oil composition of T. speciosa was very complex as reported previously [1], but the yield in the present study was higher. Caryophyllene oxide and β-caryophyllene were both detected in T. speciosa from Turkey and Serbia. However, the Turkish oil did not contain (E,Z)-farnesol and (E)-nerolidol. The AChE-inhibitory activity of the essential oil was 8±1% at 10 mg/mL.