Supercritical extraction technology: a new favorite of traditional Chinese medicine extraction
Supercritical fluid extraction (SFE) is a process of extracting and separating specific components from liquids or solids by utilizing the high solubility of supercritical fluids to solutes under supercritical conditions. There are many substances that can be used as supercritical fluids, but considering the low cost, low critical temperature and pressure, low latent heat of evaporation, safety and environmental protection, supercritical fluids widely used for extraction are carbon dioxide.
The supercritical CO2 extraction (SFE-CO2) process is different according to different extraction objects and tasks. The simplest process can be divided into extraction section and separation section, in which the extraction section refers to the transfer of solutes from raw materials to carbon dioxide fluid, and the separation section refers to the separation of solutes and carbon dioxide and the separation of different solutes. In the actual operation of SFE-CO2, there are many factors, such as extraction pressure, extraction temperature, particle size of raw materials, CO2 flow rate and CO2 entrainer, etc. So the extraction process is different.
Application of Supercritical Extraction in the Extraction of Traditional Chinese Medicine
At present, supercritical fluid extraction (SFE) technology can be used to extract and separate the effective components of single Chinese medicine and compound Chinese medicine preparations. Especially for the extraction of single traditional Chinese medicine is more extensive, mainly including the extraction of volatile oil, alkaloids, flavonoids, quinones, coumarins, lignans, saponins, polysaccharides and so on.
Essential oils are the most suitable components for supercritical CO2 extraction. The boiling point of volatile oils is low, the relative molecular weight and polarity are small, and most volatile oils are easily oxidized and decomposed by common water distillation or steam distillation due to their unstable properties. Supercritical CO2 extraction can avoid the oxidation and decomposition of the effective components in volatile oil because of its low extraction temperature.
Alkaloids mostly exist in plants in the form of organic salts, inorganic salts, esters, glycosides and so on. The solubility of supercritical CO2 fluid is low. Therefore, alkaline reagents are generally needed to pretreat them, and appropriate entrainers such as methanol, ethanol, acetone and chloroform are needed to improve their solubility.
Several common extraction methods of flavonoids are alcohol extraction, alkali water extraction and hot water extraction. Supercritical fluid extraction is a very efficient extraction technology.
The polarity of quinones is very large, so when supercritical CO2 extraction is used, higher pressure is often needed, and suitable entrainers, such as ethanol solutions of different concentrations, are also needed. In addition, when using supercritical CO2 to extract ginseng, Platycodon grandiflorum, licorice and other main components of saponins, because saponins are composed of saponins and sugar, glucuronic acid or other organic acids, generally soluble in water, but also have strong polarity, so it is necessary to add entrainers or increase pressure to improve its yield.
With the improvement of people's living standard and the emphasis on beauty and health, people are more and more advocating "returning to nature". Supercritical CO2 extraction, as a new chemical separation technology, has become a traditional Chinese medicine extraction because of its advantages of purity, safety, activity of active ingredients, non-thermal decomposition, strong stability and high extraction rate. A new extraction and separation method with considerable development potential in industry. But traditional Chinese medicine compound prescription is the mainstream of traditional Chinese medicine. At present, SFE-CO2 technology mostly stays in the extraction of single active ingredients or intermediate raw materials of traditional Chinese medicine, so we should strengthen technological innovation in the extraction of compound prescription or grouping extraction. In addition, the extraction of traditional Chinese medicine by SFE-CO2 has the same composition and content as that of traditional Chinese medicine. The same question. Therefore, when using supercritical fluid extraction technology to develop new preparations of traditional Chinese medicine, we should consider not only the extraction efficiency of effective parts, but also the pharmacological effect. Supercritical fluid extraction (SFE) technology can truly reflect its vitality or potential in this field only if it has superior technology and guaranteed or better pharmacological and clinical effects.