Supercritical fluid extracts

The use of supercritical fluids as a vehicle for extracting active ingredients from plant matrices is a modern and viable alternative to extraction systems using organic solvents (e.g., hexane). One particularly used gas is carbon dioxide, CO2, which reaches the supercritical state at a temperature of 31°C and a pressure of 72.9 atm. In the supercritical state, there is no longer a distinction between the vapor and liquid phases, and a gas under such conditions can have some properties (e.g., density or solvent power) similar to a liquid and others (e.g., viscosity) similar to a gas.

Supercritical carbon dioxide extraction offers several advantages:

• CO2 is colorless and odorless,
• At the end of extraction it is converted back to gas, returning the system to ambient temperature and pressure, so it leaves no residue in the extract obtained,
• In the supercritical state, CO2 takes on polarity characteristics and solvent power comparable to hexane, solubilizing mainly apolar compounds,
• CO2 is chemically inert, so it does not react with the phytoconstituents present in the plant matrix,
• By reaching the supercritical state at low temperature, it allows gentle extraction that does not damage the less stable phytoconstituents,
• Critical temperature and pressure are easily achieved,
• By varying the pressure and temperature of carbon dioxide in the supercritical state, or by adding cosolvents such as ethanol or water, its solubilizing properties can be modulated to optimize the extraction of the desired active ingredients,
• it is an economical gas,
• It is non-toxic to the environment, does not damage the ozone layer, and is recyclable.

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