Isolation using supercritical carbon

Reverchon E, Ambruosi A, Senatore F. Isolation of peppermint oil using supercritical carbon dioxide extraction. Flavour Fragrance J 1994 9 19-23. 

Supercritical fluid extraction (SEE) using supercritical carbon dioxide (SC-CO2) has been successfully used for isolation of volatile nitrosamines from different matrices such as tobacco and food products. This technique presents several advantages with respect to other extraction methods (e.g., mineral oil distillation or low-temperature vacuum distillation) currently used. Thus, SEE minimizes sample handling, provides fairly clean extracts, expedites sample preparation, and reduces the use of environmentally toxic solvents. Good results have also been obtained with the use of SPE in the analysis of food matrices combining extraction with Extrelut sorbent and purification with Florisil. This method is applicable for the analysis of a range of the most widely encountered volatile N-nitrosamines, including the poorly volatile NDBA, NDBzA, and N-nitroso-N-methylaniline in various food products. Active carbon is suitable for this preconcentration step due its low cost, versatility, and easy application. 

Zhao Y, Sheng G, Wang D. 2000. Pilot-Scale Isolation of Tocopherols and Phytosteiols from Soybean Sludge in a Packed Column Using Supercritical Carbon Dioxide. 5th International Symposium on Supercritical Fluids (ISSF). Atlanta, Georgia. 

The reaction of a carboxylic acid with N,Af -carbonyldiimidazolellH33 (abbreviated as CDI), forming an imidazolide as the first step followed by alcoholysis or phenolysis of the imidazolide (second step), constitutes a synthesis of esters that differs from most other methods by virtue of its particularly mild reaction conditions.t41,[5] It may be conducted in two separate steps with isolation of the carboxylic acid imidazolide, but more frequently the synthesis is carried out as a one-pot reaction without isolation of the intermediate. Equimolar amounts of carboxylic acid, alcohol, and CDI are allowed to react in anhydrous tetrahydrofuran, benzene, trichloromethane, dichloromethane, dimethylformamide, or nitromethane to give the ester in high yield. The solvents should be anhydrous because of the moisture sensitivity of CDI (see Chapter 2). Even such unusual solvent as supercritical carbon dioxide at a pressure of 3000 psi and a temperature of 36-68 °C has been used for esterification with azolides.[6]... 

Isolation of Organic Compounds Present in Water at Low Concentrations Using Supercritical Fluid Carbon Dioxide... 

Gordon and Holmes32 used a supported triphenylphosphine-Pd(II) complex as an effective catalyst for Heck and Suzuki couplings in supercritical carbon dioxide (entry 27). After optimization of the amine base for the reaction, the final products have been isolated in good yields and high purity with no traces of metal. 

Plants and plant extracts have been used as medicine, culinary spice, dye and general cosmetic since ancient times. Plant extracts are seen as a way of meeting the demanding requirements of the modem industry. In the past two decades, much attention has been directed to the use of near critical and supercritical carbon dioxide solvent, particularly in the food pharmaceutical and perfume industries. CO2 is an ideal solvent because it is non-toxic, non-explosive, readily available and easily removed from the extracted products. At present the major industrial-scale applications of supercritical fluid extraction (SFE) are hop extraction, decaffeination of coffee and tea, and isolation of flavours, fragrances and other components from spices, herbs and medicinal plants [1-4]. 

Microcystins are an increasingly important group of bioactive compounds, produced mainly by planktonic cyanobacteria. They are a family of cyclic heptapeptides that cause both acute and chronic toxicity. Purified microcystins are utilized in a range of research applications. This review summarizes the isolation of microcystins from the cyanobacteria by supercritical fluid extraction (SFE). The microcystins can be successfully extracted when a modifier is used in supercritical carbon dioxide fluid. The advantage of the method is that the sample handling steps are minimized, thus reducing possible losses of microcystin and saving extraction and purification time. 

In the present investigation, supercritical carbon dioxide and carbon dioxide -h co-solvent mixtures were used to extract and isolate a model pyrrolizidine alkaloid from its parent plant. Pyrrolizidine alkaloids have been used in herbal medicine to combat tumors as long ago as the fourth century A.D. (4) and to treat cancer since the tenth century A.D. (5). More recently, they have received increasing attention as chemotherapeutic drugs. Processes for their separation, however, are specific to each alkaloid, and either lead to chemical modification of the alkaloid or require the use of solvents which must then be completely removed from the extract. 

The use of critical fluids for the extraction and refining of components in natural products has now been facilitated for over 30 years. Early success in the decaffeination of coffee beans and isolation of specific fractions from hops for flavoring beer, using either supercritical carbon or liquid carbon dioxide, are but two examples of the commercial application of this versatile technology. Critical fluid technology, a term that will be used here to embrace an array of fluids under pressure, has seen new and varied applications which include the areas of engineering-scale processing, analytical, and materials modification. 

The first report on DFA formation in higher plants dates back to 1933, when Schlubach and Knoop [23] isolated a compound tentatively identified as a-D-fructofuranose p-o-fmctofuranose l,2 2,l -dianhydride (10, also known as DFA I) from Jerusalem artichoke. Alliuminoside, a difructofuranose 2,6 6,2 -dianhydride for which configuration at the glycosidic linkages was not determined, was isolated from tubers of Allium sewertzowi [24], However, the fact that these results have not been further confirmed throws some doubt onto whether the DFAs were actually from plant origin or were formed by the presence of microorganisms. The enzymic formation of a-o-fructofuranose p-o-fructofuranose l,2 2,3 -dianhydride (1, DFA HI) in sterilized homogenates of the roots of Lycoris radiata, a plant use in China as a traditional folk medicine, unequivocally demonstrated the capacity of this plant to produce this particular DFA [25]. The compound was further extracted from the intact bulbs by supercritical carbon dioxide and its structure unequivocally established by NMR [26]. 

Maheshwari, P. E.T. Ooi Z.L. Nikolov. Off-flavor removal from soy protein isolate by using liquid and supercritical carbon dioxide./. Am. Oil Chem. Soc. 1995, 72, 1107—1115. 

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