Polyol-induced partitioning of essential oils in water/acetonitrile solvent mixtures

Abstract

ABSTRACTPolyol-induced extraction (PIE) is applied to the extraction of essential oils, using glycerol as a mass separating agent. In 1:1 acetonitrile (ACN)/water solvent mixtures, two immiscible phases can be generated. PIE as an alternative extraction technique was assessed by the extraction of the main flavor and fragrance compounds that comprise six essential oils. In the extraction of eugenol (4-allyl-2-methoxyphenol) from clove buds, the partition coefficients were determined and the % recovery and thermodynamic data in the temperature range of −20 to 20°C were calculated. The main components present in each essential oil extract were identified through gas chromatography/mass spectrometry (GC/MS) and the compositional profile was compared to traditional extraction techniques. The optimized extraction conditions (−10°C, 1:1 ACN/water (v/v), 20% glycerol) for eugenol at −10°C give a partition coefficient (KPC) of 87 and an extraction efficiency of 97% in the acetonitrile-rich phase. The eugenol migration to the organic phase is a spontaneous process (ΔG° = −9.3 kJ/mol) and an endothermic process (ΔH° = 9.2 kJ/mol) with entropy being the driving force behind the reaction (ΔS° = 70 J/K, TΔS° = 18.4 kJ). The technique was applied to five other essential oils (cinnamon bark, caraway seed, spearmint leaf, peppermint leaf, and anise seed oils) with similar results.