Comparison of essential oil composition of Carum copticum obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of Carum copticum cultivated in Iran was obtained by hydrodistillation and supercritical (CO2) extraction (SFE) methods. The oils were analysed by capillary gas chromatography, using flame ionization and mass spectrometric detection. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters, such as pressure, temperature, modifier volume and extraction time, on the supercritical fluid extraction of C. copticum oil were investigated. The results showed that, under pressure of 30.4 MPa, temperature 35 °C, methanol 0% and dynamic extraction time of 30 min, the method was most selective for the extraction of thymol. Eight compounds were identified in the hydrodistilled oil. The major components of C. copticum were thymol (49.0%), γ-terpinene (30.8%), p-cymene (15.7), β-pinene (2.1%), myrcene (0.8%) and limonene (0.7%). However, by using supercritical carbon dioxide under optimum conditions, only three components constituted more than 99% of the oil. The extraction yield, based on hydrodistillation was 2.8% (v/w). Extraction yield based on the SFE varied in the range of 1.0–5.8% (w/w) under different conditions. The results show that, in Iranian C. copticum oil, thymol is a major component.