Development of a Green Alternative Procedure for the Simultaneous Separation and Quantification of Clove Oil and Its Major Bioactive Constituents

Clove buds are a good source of oil, which can be used as a food flavor and traditional Chinese medicine. To isolate clove oil and its major bioactive constituents, a green alternative procedure employing ultrasound-assisted supercritical carbon dioxide (USC–CO₂) extraction combined with gas chromatography/mass spectrometry was developed, and its performance was compared to those of conventional processes. The green USC–CO₂ process saves time, solvent, energy, and raw materials without chemical waste while achieving superior yields of clove oil and major bioactive constituents. The solubility of clove oil and fictitious solubility of eugenol in SC–CO₂ have been predicted for the first time at various temperatures (32–50 °C) and pressures (9.0–28.5 MPa). Furthermore, solubility data correlated well with three density-based models (Chrastil, Kumar–Johnston, and Bartle), and the overall average absolute relative deviations (AARD%) were 0.22, 0.92, and 4.91%, respectively. Using correlation results, we approximated the enthalpies for clove oil. The total heat of solution, heat of solvation, and heat of vaporization for clove oil were 9.83, 19.03, and −9.69 kJ/mol, respectively.