Subcritical extraction of extracts

China's vast territory, complex geography and variable climatic conditions have created a diversity of species in China, especially the special oils and fats, flavors and fragrances, pigments and other natural resources with health care effects are quite abundant, such as ginkgo, clove, ginger, garlic, onion, wolfberry seeds, sea buckthorn, red pepper, pepper, osmanthus, rose and jasmine, and so on.

Extracts of natural products can be widely used in medicine, food, cosmetics, health care and biological products. It has been particularly valued and favored, especially botanical drugs are developing rapidly in the international market. According to statistics, the global market value of botanical medicine is close to 40 billion dollars, and the market outlook is favorable. As the birthplace of traditional Chinese medicine in China, the production of natural botanical products accounted for only 3% of the international market, and in this extremely limited export volume, the vast majority of raw materials are still primary products, the main reason for this is the existence of production technology in China is technologically backward, low level of engineering, low degree of equipment modernization and other issues.

Research and development of natural products active ingredient extraction technology

Based on the natural product raw materials in a variety of components of compounds in different solvents, in accordance with the principle of "similar solubility", the choice of the required active ingredient solubility, do not need to dissolve out of the components of the solvent solubility of the solvents, the active ingredient from the raw material tissue dissolved in the raw material, and the solubility of the active ingredient. Active ingredients from the raw material tissue dissolved out, and then distilled to recover the extraction solvent to complete the extraction, separation process. Traditional extraction solvents are strong polar solvent water and polar organic solvents ethanol, methanol, acetone, etc., ethanol is most commonly used; lipophilic organic solvents, such as petroleum ether, benzene, chloroform, ethyl ether, ethyl acetate, dichloroethane, propane, butane fluids, as well as supercritical CO2 fluids.

Traditional extraction methods for active ingredients of natural products

Traditional extraction methods involve loading raw materials into appropriate containers, adding suitable solvents, such as ethanol, water or CO2 fluid, etc., and controlling the size of raw materials, extraction time, extraction temperature, extraction pressure and other process conditions, in order to dissolve the active ingredients. Commonly used methods are:

A. Leaching extraction method: impregnation, percolation, decoction, reflux extraction method and continuous reflux extraction method, etc.;

B. Water vapor distillation: the raw materials and water together with the heating, when the sum of its vapor pressure and the vapor pressure of the water for an atmospheric pressure, the liquid began to boil, and the water vapor will be volatile substances and brought out. For example, volatile oil, some small molecules of alkaloids, as well as some small molecules of phenolic substances;

C. Sublimation method: solid substances heated directly gasification, condensation and solidification of solid compounds, the use of the principle of sublimation directly from the raw materials in the extraction of the target components. For example, the sublimation of camphor in camphor, caffeine in tea.

Traditional processes such as impregnation, percolation, decoction, reflux extraction and continuous reflux extraction, extraction capacity, selectivity, but in the extraction, separation process, the process temperature is more than 50 ℃ or more, easy to cause "heat-sensitive" active ingredient decomposition or denaturation to varying degrees, so that the product occurs in a secondary Biochemical; lipophilic organic solvent extraction of the product produced by the solvent residue is high, reducing the quality of the product, and can be selected organic solvents are mostly flammable, the production process is difficult to eliminate the safety hazards. Water vapor distillation method, sublimation method due to its targeted too strong, affecting the application of the method of the field.

New methods for extraction of active ingredients of natural products

In recent years, ultrasound, microwave-assisted extraction method and supercritical carbon dioxide fluid extraction method are also widely used at home and abroad. Ultrasonic extraction method, that is, the use of ultrasound "cavitation" effect, in order to stimulate the extraction of solvent permeation, dissolution, diffusion activity of the extraction process. Supercritical carbon dioxide fluid extraction method, need to control the CO2 at the critical temperature (31.05 ℃) and critical pressure (7.38MPa) above, so that the CO2 is in the supercritical temperature and supercritical pressure state and has the dual characteristics of gas and liquid, as a solvent, through intermolecular interactions and diffusion to dissolve raw materials of the target components, the formation of supercritical CO2 loading phase, and then Reduce the pressure of the carrier gas or increase the temperature, so that the solubility of supercritical CO2 is reduced, so as to achieve the purpose of extraction and separation.

The ultrasonic extraction method is a major improvement on the traditional process methods, has a better economy and wide adaptability, but is only an auxiliary means, need to be combined with other extraction technology to play a role. Supercritical CO2 extraction method has the advantages of strong extraction capacity, high extraction rate, high selectivity and good product quality. However, CO2 must be above 25MPa under ultra-high pressure to be able to carry out the extraction process, the extremely high pressure limits the effective volume of the equipment to enlarge, but also restricts the technology in the production of natural products in the industrialization of the application.