Comparison of essential oils compositions of Ferula assa-foetida obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of Ferula assa-foetida, cultivated in Iran, was obtained by hydrodistillation and supercritical (carbon dioxide) extraction methods. The oils were analysed by capillary gas chromatography using flame ionization and mass spectrometric detections. 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 (SFE) of Ferula assa-foetida oil were investigated. The results showed that, under a pressure of 300 atm, temperature 35 °C, 5% methanol and dynamic extraction time of 25 min, extraction was more selective for the E-1-propyl sec-butyl disulfide. Twenty five compounds were identified in the hydrodistilled oil. The major components of Ferula assa-foetida were E-1-propenyl sec-butyl disulfide (40.0%) and germacrene B (7.8%). However, by using supercritical carbon dioxide under optimum conditions, only two components constituted more than 70% of the oil. The extraction yield, based on hydrodistillation, was 1.13% (w/w). Extraction yield, based on the SFE, varied in the range of 0.8-5.5% (w/w) under different conditions. The results show that, in Iranian Ferula assa-foetida oil, E-1-propyl sec-butyl disulfide is a major component.