Herbs, phytochemical extraction from

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

Table 9.4. Extraction of phytochemicals from herbs using emerging technologies.

Temperature and pressure. Most of the studies for the extraction of phytochemicals from herbs using SC-CO2 were performed at temperatures of 40-70°C and pressures of 14 10 MPa (see Table 9.4). The influence of temperature and pressure using... 

Flow rate and extraction time. No report was found for the effect of flow rate in the extraction of phytochemicals from herbs. Extractions at lower pressures and/or temperatures required prolonged time and large amounts of CO2 to achieve the same yield as reported for the extraction of caffeine, theophylline, and theobromine from mate tea leaves (Saldana and others 1999,2002a). 

Basil is another Lamiaceae herb primarily used for culinary purposes and it is grown in subtropical regions all over the world with nearly 150 different species. However, different cultures have traditionally used basil as a means to treat warts, constipation, kidney malfunctions, bronchitis, and sore throats (Javanmardi et al 2003 Vieira and Simon 2000). Evaluations of secondary metabolites in basil have revealed an array of phytochemicals that include monoterpenes, sesquiterpenes, and aromatic compounds (Juliani and Simon 2002). Ethanolic extracts and preparation of essential oils from a variety of basil species were shown to have high antioxidant properties in vitro (Juliani and Simon... 

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