Comparison of essential oil composition of Iranian fennel (Foeniculum vulgare) obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of fennel 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 (El, 70 eV). The effects of different parameters, such as pressure, temperature, modifier volume and extraction time, on the supercritical fluid extraction of fennel oil were investigated. The results showed that, under pressure of 350 atm, temperature 55 degreesC, methanol 5% and dynamic extraction time of 45 min, extraction was more selective for the extraction of (E)-anethol. Sixteen compounds were identified in the hydrodistilled oil. However, by using supercritical carbon dioxide in optimum conditions, only nine components represented more than 99% of the oil. The results showed that, in Iranian fennel oil, (E)-anethol is a major component. Copyright (C) 2002 John Wiley Sons, Ltd.