| As the development of the natural medicine, the glycyrrhizin extracted from the licorice root was found to have potential therapeutic value in the treatment of several diseases, especially available for anti-SARS virus. Therefore, an optimal method to extract and refine the glycyrrhizin can be found. In that case, the extraction of glycyrrhizin by means of organic solvents and supercritical carbon dioxide (SC-CO2) was investigated. The extraction of glycyrrhizin from licorice root with supercritical carbon dioxide was also compared with conventional extraction methods. Those methods include the extraction at room temperature (ERT), the traditional Soxhlet extraction, and the heat reflux extraction. The results show that the yield obtained by SC-CO2 extraction was similar to that obtained by conventional solvent extraction. But the quality of the production extracted by SC-CO2 was better than that of the production extracted by other methods. Subsequently, HPLC was used to analyze the chemical compositions of these productions.
Licorice is herbaceous triennial or perennial plant, with large roots. The roots and the stalks are used extensively fields, tobacco, food, flavoring, confectionery, perfumes, pharmaceutical industry, etc. Particularly in medicine licorice has a lot of virtue. Glycyrrhiza radix has been used as a Chinese traditional medicine for over 1000 years. It was used to relieve a cough, reduce phlegm, detoxifcation. At present, the medicine is frequently used to treat diseases such as contagious hepatitis, bronchitic asthma, canker, ague, antivirus, and improve immunity. Especially, glycyrrhizic acid was found to have the ability to restain HIV reproduce in 1980s. Subsequently, the flavonoids were also found to have this function. Glycyrrhizin, which is also called glycyrrhizic acid, could be used treatment for sudden acute respiratory syndrome (SARS). Glycyrrhizin may protect the target cell from the SARS virus to attach to and invade. It also hinders virus reproductions and spread from one cell to another cell. As the development of the medicine, the demand of glycyrrhizin, flavonoids and other availability enlarge widely. The application of supercritical fluid extraction (SFE), particularly the use of liquid and supercritical carbon dioxide, has received much attention in Glycyrrhiza radix extraction in the last few years. This separation technique offers extraction yields comparable with those obtained by conventional extraction methods using organic solvent, followed by column separation and purification, to obtain pure compounds. The conventional extraction consumed large amounts of solvent, required lots of time, and polluted the environment. Since carbon dioxide has some advantages: chemically inert, nontoxicity, nonflammable, no pollution problem, and shorter concentration time. These advantages attract the researchers’ interest in using supercritical carbon dioxide to extract Glycyrrhiza radix. For the extraction of polar or ionic compounds, organic solvents have been added as the cosolvent to increase the compounds’ solubility in SC-CO2. The extractions, which have been used extensively, have three components: glycyrrhizin, flavonoids, amylose. There are many methods to extract glycyrrhiza radix, such as traditional extraction, heat reflux extraction, ultrasonic extraction, microwave-assisted extraction, SC-CO2 extraction. These extraction methods have been compared.
SC-CO2 technology have been used to plant extract widely. SC-CO2 extraction was a very suitable method for licorice. Briefly, sample was accurately weighed, then extracted by the following methods. The pulverized sample was packed into a sample cartridge.
It is important that extraction pressure is one of the most parameters. Different material has different condition, which is been determinate by the polar of the material. Nonpolar material is extracted at lower pressure, but polar is extracted at higher pressure. Since glycyrrhizic acid and flavonoids are all polar materials, the experiment’s pressure is selected at higher pressure. Temperature is another important parameters. The effect of temperature is very complex. At a certain pressure, if the temperature is been enhanced the molecular distance is increased and the affects among the molecules are decreased which cause the solubility reduced. Another aspect, enhanced the temperature can cause the vapor pressure of the extraction increase and increase the combine between molecules, so the solubility increased. However, high temperature can make the production quality decrease. So the whole experiment at lower temperature.
The cosolvent is added in this experiment to increase the solubility of glycyrrhizin and flavonoids in SC-CO2. Because SC-CO2 is a nopolar solvent, so it makes glycyrrhizin and flavonoids hard to dissolve in it. The ethanol as cosolvent is added into SC-CO2 in order to increase the solubility of glycyrrhizin and flavonoids.
Fig. 63 Effect of ethanol concentration on the yield
Milling of the raw materials greatly improves the extraction efficiency. The smaller particle size should gain the greater yield. But too small particle size may be increase the flow resistance.
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