Extraction, properties, and chemical compositions of essential oils from wildly growing Limnocitrus littoralis (Miq.) Swingle species in Southcentral coast of Vietnam
Description
Extraction of essential oils: The materials and distilled water were added to a 2000 ml round bottom flask submitted to hydrodistillation using the Clevenger apparatus and the 500-watt heating mantle. Each of the distillate oil samples was extracted with 15 mL of diethyl ether (3 x 15 ml). Ethereal solutions were dried with anhydrous sodium sulfate (Na2SO4). Remove Na2SO4 by a filter. The anhydrous ether was recovered from the filtrate by rotary evaporation. The pure essential oil was collected and stored in a dark glass bottle placed in the fridge. Properties of essential oils: Organoleptic properties, physical properties were determined by AFNOR (French Association of Normalization) standards or ISO (International Organization for Standardization) standards (specific gravity/ISO 279:1998, refractive index/ ISO 280:1998, optical rotation/ISO 279:1998), at 25 oC.[14] The chemical properties inclduing the acid value and saponification value were carried out based on ISO 1242:1999 and ISO 3657:2020, respectively. Chemical compositions of essential oils *GC/FID: Analyses were performed on an Agilent gas chromatography 6890N GC, equipped with a Phenomenex 7HG-G010-11 Zebron ZB-5 GC capillary column (30 m x 0.32 mm x 0.25 µm). Nitrogen was used as the carrier gas at the flow rate of 1.74 ml/ min. The constant pressure mode at 9.32 psi was used and the oven temperature was programmed from 60 oC to 240 oC at the rate of 3 oC/min. The injector and detector temperature were set at 250 oC. Oil samples of 0.1 μl were injected with splitless mode. *GC/MS method: The oil was analysed by an Agilent gas chromatography 7890A, equipped with a Phenomenex 7HG-G010-11 Zebron ZB-5 GC capillary column (30 m x 0.32 mm x 0.25 µm), coupled to an Agilent Mass Selective Detector 5975C VL MSD Triple-Axis. Helium was used as the carrier gas at a flow rate of 1.20 mL/min. The constant pressure mode at 13.209 psi was chosen on the GC program. The injection temperature was 250 oC; the injection volume was 1.0 µL; the split ratio was 1:25, and the ionization voltage was 70 eV. The oven temperature was programmed from 60 oC to 240 oC at the rate of 3 oC/min. The detector was set at 250 oC. *Identification of essential oil constituents: GC/MS data of spectra were used for interpreting names of constituents in essential oils by comparing their mass spectra with those of standard compounds registered in the NIST 2014 and NIST 2020 libraries. Moreover, the identification was also confirmed by collating the observed LRI (linear retention indices) of each constituent with those reported in the compilation of retention indices published by Adams. The observed LRI was calculated by using the equation propounded by van den Dool and Kratz to the homologous series of C9-C20 n-alkanes (Sigma-Aldrich). The relative percentage of each constituent in the oil was determined by peak area normalization.