A Comparison between the Chemical Composition of the Oil Solvent Extract and Supercritical Carbon Dioxide Extract of Citrus medica cv. Diamante

Citrus medica L. cv. Diamante collected in Calabria (Italy) was extracted by different technologies. The traditional hydrodistillation and solvent methods were compared to the supercritical carbon dioxide extraction (SCF-CO2) performed at two fluid densities: the lowest at 250 g/dm3 and the highest at 875 g/dm3. The effect of the drying process on the peels was studied, and the oil loss was found to be low. The solubility power of CO2 (related to its density) was observed. An enrichment of the less-volatile components like sesquiterpenes, heterocyclic compounds and waxes was quantified in the SCF-CO2 extracts. The monoterpene hydrocarbons were about 95% in the hydrodistillates and in the pentane extract, but these components decreased in the SCF-extracts to a value lower than 85%. The sesquiterpenes were about 0.62% in the hydrodistillates and 1.40% in the pentane extract, but high quantities were found in the SCF-CO2 extracts: 5.64% in the extraction performed at low CO2 density and 12.09% at high CO2 density. In particular, the SCF-CO2 extract was determined to be rich in phytol and citropten. The high content of waxes in SCF-CO2 extract at high fluid density is proved by the dilution of the volatile components. Limonene was about 60 g in 100 g of the hydrodistilled, but only 4.5 g was in 100 g of SCF-CO2 extract at 875 g/dm3 of CO2 density, in the same a decrease of other terpenes was quantified. Differences in the ratio of some monoterpene hydrocarbons were also observed when compared to literature data