Abstract
An overview of the studies carried out in our laboratories on supercritical fluid extraction (SFE) of volatile oils from seven aromatic plants: pennyroyal (Mentha pulegium L.), fennel seeds (Foeniculum vulgare Mill.), coriander (Coriandrum sativum L.), savory (Satureja fruticosa Béguinot), winter savory (Satureja montana L.), cotton lavender (Santolina chamaecyparisus) and thyme (Thymus vulgaris), is presented. A flow apparatus with a 1 L extractor and two 0.27 L separators was built to perform studies at temperatures ranging from 298 to 353 K and pressures up to 30.0 MPa. The best compromise between yield and composition compared with hydrodistillation (HD) was achieved selecting the optimum experimental conditions of extraction and fractionation. The major differences between HD and SFE oils is the presence of a small percentage of cuticular waxes and the relative amount of thymoquinone, an oxygenated monoterpene with important biological properties, which is present in the oils from thyme and winter savory. On the other hand, the modeling of our data on supercritical extraction of volatile oil from pennyroyal is discussed using Sovová’s models. These models have been applied successfully to the other volatile oil extractions. Furthermore, other experimental studies involving supercritical CO2 carried out in our laboratories are also mentioned.
Highlights
According to the European Pharmacopeia [1] the essential oil is the extract from aromatic plants obtained mainly by distillation processes, like hydrodistillation (HD) and steam distillation (SD)
The aim of this work is to give an overview of our experimental work on supercritical extraction of volatile oils with several aromatic plants
Quantitative analysis was performed in a Hewlett-Packard 5890 gas chromatograph, using a flame ionization detector (FID) and a fused-silica DB-5 capillary column (J&W Scientific Inc, Folsom, CA, USA; 30 m × 0.25 mm i.d., film thickness 0.25 μm)
Summary
According to the European Pharmacopeia [1] the essential oil is the extract from aromatic plants obtained mainly by distillation processes, like hydrodistillation (HD) and steam distillation (SD). The essential oils of plants comprise monoterpenes and sesquiterpenes, plus their oxygenated derivatives, mainly alcohols, aldehydes and ketones, which are important in the food, cosmetic and pharmaceutical industries. These traditional extraction techniques can affect the quality of essential oil, since the degradation of thermolabile compounds, as well as the hydrolysis and hydrosolubilization of some compounds can occur. SFE with CO2 is an environmental friendly technique, very suitable to obtain different plants extracts, because manipulations of the process parameters, such as temperature and pressure of the supercritical fluid, can change its solvent power. The most serious drawback of SFE, when compared with traditional atmospheric pressure extraction techniques, is the higher initial investment cost of the equipment
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