Supercritical Fluid Extraction of Essential Oil Components from Lemon-Scented Botanicals

Essential oils were extracted from four different varieties of lemon-scented plants utilizing supercritical fluid extraction. The plants used included: lemon eucalyptus (Eucalyptus citriodora), lemon balm (Melissa officinalis), lemon bergamot (Monarda citriodora), and lemongrass (Cymbopogon citratus). Extracts from three plants of each species were analysed using gas chromatography and confirmed with GC–MS. The compounds identified for each plant species were: lemon balm (citronellal, neral, geranial, neral acetate, caryophyllene, and caryophyllene oxide), lemon bergamont (thymol, thymol methylester, and α -terpine), lemon eucalyptus (citronellal, neral, caryophyllene, and caryophyllene oxide), and lemongrass (neral, geranial, and caryophyllene). Supercritical fluid extractions were performed at three pressures (13,790, 27,580, and 41,370 kPa) and two extraction temperatures (40 and 60 °C). The results indicated that the mass percent extracted increased with increasing temperature and pressure, as was the ratio of the compounds in the different samples. The effect of particle size reduction on the extraction yield was also investigated. The extraction yield did not increase due to the increase in surface area as would be expected, but decreased. This has been attributed to the fact that the compounds of interest are extremely volatile and were lost to the atmosphere during the grinding process.