AChE-inhibitory properties and the chemical composition of Salvia aethiopis L. essential oil

Abstract

Previously, the hydrodistilled essential oil of the aerial parts of Salvia aethiopis L. (Lamiaceae) from Erzurum–Turkey was reported to contain germacrene D (29.0%), α-copaene (19.8%), β-cubebene + β-elemene (9.9%), bicyclogermacrene (9.3%), δ-cadinene (8.7%), and β-caryophyllene (7.3%) [1]. The current study aims to provide information on the essential-oil composition of the aerial parts of S. aethiopis from another location in Turkey. The plant material used in this study was collected from Tokat in June 2017. The essential oil was obtained by hydrodistillation (3 h) of air-dried aerial parts using a Clevenger-type apparatus, in a yield of 0.09 mL per 100 g of plant material. The essential oil was diluted with n-hexane 1:10 (v/v) 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. Eighty-one compounds were identified comprising 90.1% of the detected oil constitutes. The main components of the oil of S. aethiopis from Tokat were α-copaene (17.8%), germacrene D (12.7%), bicyclogermacrene (11.8%), β-caryophyllene (6.9%), and δ-cadinene (4.3%). The results agreed generally with the literature ones except for the variation in the percentage of the main components. Additionally, AChE-inhibitory properties of the essential oil were investigated and the oil was demonstrated to inhibit 46.4±0.8% (n = 3) of AChE activity, at 1 mg/mL.