Supercritical CO2 Extraction of Herbal Drugs
Ram B Gupta,
Associate Dean for Research School of Engineering,
Virginia Commonwealth University
High quality plant/herb extracts can be obtained by use of supercritical extraction. Typically, herbs are contacted with compressed CO2 at about 80 bar and 40 oC to dissolve the active components, and then pressure is reduced to recover the product concentrate in the recovery vessel. The compositions of the extracts are different than those from traditional solvent or steam extractions. Supercritical CO2 efficiently extracts most lipophilic components, and can extraction some hydrophilic components with the use of a suitable co-solvent. Use of ultrasonic mixing can further enhanced the extraction efficiency. Supercritical fluid extraction has been well accepted for coffee decaffeination and is being applied in other food, cosmetics, and pharmaceutical applications. Benefits of the supercritical carbon dioxide extraction include (1) oxygen-free system prevents oxidation of the extract; (2) low temperature minimizes the thermal degradation; (3) microbes or their spores are not soluble, hence aseptic extracts are obtained; and (4) solvent-free extract is obtained because CO2 is gas at ambient and is not retained by the extract. The application of supercritical extraction in herbal drugs is expanding. Some of the recent cases of herbal extraction will be discussed that have led to clinical use.
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