Ultrasound-assisted extraction and quantitation of oils from Syzygium aromaticum flower bud (clove) with supercritical carbon dioxide

•USC–CO2 extraction increased the yield while using less severe operating conditions.•The yield was improved by 20.8% using USC–CO2.•The extraction time was decreased, and no organic solvents were used.•Oil extraction from clove followed second-order extraction kinetics.•Cloves proved to be a suitable source for clove oil production.

This study evaluated ultrasound-assisted supercritical carbon dioxide (USC–CO2) extraction for determining the extraction yields of oils and the contents of eugenol, β-caryophyllene, eugenyl acetate and α-humulene from clove buds. Compared to traditional SC–CO2 extraction, USC–CO2 extraction might provide a 13.5% increase in the extraction yield for the oil while utilizing less severe operating parameters, such as temperature, pressure, CO2 flow rate and the time consumed by the process. Our results were comparable to those obtained using the heat reflux extraction method, though the yield was improved by 20.8% using USC–CO2. In kinetic studies, the USC–CO2 extraction of clove oil followed second-order kinetics. The activation energy for the oil extraction was 76.56 kJ/mol. The USC–CO2 procedure facilitated the use of mild extraction conditions, improved extraction efficiency and the quality of products and is a potential method for industry.