Plant extract is a product obtained by extracting and concentrating certain effective components from plants through physical and chemical extraction and separation processes, based on the requirements of the final product's usage. It does not alter the structure of the effective components.
1. Classified by the purpose of extraction:
1) Proportional extract: It is a concentrated extract, decoction, or powder obtained by extracting and concentrating raw materials such as plants and animals. The quantity of raw materials before extraction and the mathematical ratio of the product after extraction and concentration. Proportional extracts generally do not have very clear components and contents. For example, 10 kilograms of Scutellaria baicalensis medicinal materials are extracted and concentrated into 1 kilogram of powder-like product. We call it a 10:1 Scutellaria baicalensis proportional extract. The important indicators such as scutellarein and scutellarin in this extract do not have clear standards. Proportional extracts are usually qualitatively detected by thin-layer scanning (reflection method), and the concept is relatively vague. It is not conducive to the development of the extract industry. Therefore, establishing a quality control system and standards for proportional extracts has been the consistent call of the industry for many years.
2) Standard extract: It is an extract of herbs, plants, animals, etc. with consistent standards.
Traditional Chinese medicine standard extract refers to an extract obtained by extracting and processing traditional Chinese medicinal materials using modern science and technology, which has a relatively clear content and quality (quantitative).
2. Classified by the extracted components:
Sugars: Also known as glycosides, they are formed by the combination of sugar and non-sugar substances. The commonality of sugars lies in the sugar part. Different types of aglycones have different physiological activities and various functions. For example, the leaves of Digitalis contain cardiac glycosides with strong cardiac effects, and ginseng contains ginsenosides with functions of tonifying qi, generating fluid, and calming the mind in ginseng.
Essential oil: Also known as essential oil, it is an oily liquid with aroma and volatility, a mixture of various compounds, with physiological activity, and has various functions in medicine, such as relieving cough, relieving asthma, inducing sweating, dispelling surface, promoting expectoration, repelling wind, relieving pain, antibacterial, etc. Medicinal plants with relatively high content of essential oil include Platycladus orientalis, Magnolia officinalis, Magnolia officinalis, Cinnamomum camphora, Cinnamomum cassia, Angelica sinensis, Ligusticum chuanxiong, Angelica sinensis, Mentha, etc.
Tannin (tannin): A mixture of polyphenols. It exists in many plants, especially in Salicaceae, Fagaceae, Polygonaceae, Rosaceae, Leguminosae, Myrtaceae, and Rubiaceae plants. The medicinal plant Salix viminalis has insect as the tannin, which has astringent, anti-diarrheal, and anti-sweating effects.
Other components： such as carbohydrates, amino acids, proteins, enzymes, organic acids, oils, waxes, resins, pigments, inorganic substances, etc., each having special physiological functions. Many of them are important drugs in clinical practice.
Methods of extracting plant extracts
Currently, the commonly used methods for extracting plant extracts include solvent extraction method, ultrasonic extraction method, microwave extraction method, etc., while supercritical fluid extraction method and microwave-assisted extraction method are widely used as new extraction technologies.
Solvent extraction method
Generally refers to the method of extracting the effective parts from Chinese herbal medicines. According to the solubility of various components in the solvent in Chinese herbal medicines, select a solvent with high solubility for active components and low solubility for components not to be dissolved, and dissolve the active components from the tissue of the medicinal materials by this method. When the solvent is added to the Chinese herbal medicine raw materials, the solvent diffuses and penetrates through the cell wall into the cells, dissolving soluble substances, and causing a concentration difference inside and outside the cells. The concentrated solution inside the cells continuously diffuses outward, and the solvent continuously enters the tissue cells of the medicinal materials. Multiple round trips occur until the concentration of the solution inside and outside the cells reaches a dynamic equilibrium, and the saturated solution is filtered out and new solvents are added, which can dissolve most of the required components.
Ultrasonic Extraction Method
Ultrasonic extraction utilizes the intense vibration and cavitation effect generated by ultrasonic waves to accelerate the release, diffusion, and dissolution of substances within plant cells into the solvent. At the same time, it can maintain the structure and biological activity of the extracted substances unchanged. The principle of ultrasonic extraction is mainly a physical process and has gradually gained attention as a relatively new extraction method in recent years. For most components, the ultrasonic extraction method can significantly shorten the extraction time compared to conventional solvent extraction, consume less solvent, have a higher extraction rate, and thus has a higher extraction efficiency. During the ultrasonic extraction process, the selection of the solvent, its concentration, the ratio of material to liquid, the extraction temperature, and the extraction time will directly affect the extraction rate.
Supercritical Fluid Extraction Method
Supercritical fluid extraction is the most advanced physical extraction technology in the world, abbreviated as SFE (supercritical fluid extraction). At a relatively low temperature, as the pressure of the gas increases continuously, it will transform into a liquid. When the pressure increases further, the volume of the liquid expands. For a specific substance, there always exists a critical temperature (Tc) and a critical pressure (Pc). Above the critical temperature and critical pressure, the substance will not become a liquid or a gas. This point is the critical point. Within the range above the critical point, the state of the fluid is between gas and liquid. The fluid within this range is called a supercritical fluid (SF). Supercritical fluids have a stronger penetrating power similar to gases and a larger density and solubility similar to liquids. They have good solvent properties and can be used as solvents for extraction and separation of monomers.
Microwave-assisted extraction method
Microwave-assisted extraction technology is a new technology that utilizes microwave energy to enhance extraction efficiency. Microwave-assisted extraction is a method that selectively extracts target components from materials by taking advantage of the heating characteristics of microwaves. By adjusting the parameters of microwaves, the target components can be effectively heated, facilitating the extraction and separation of the target components.
