1. Principles of Microwave-Assistant Chinese Medicine Extraction
Microwave energy is a form of energy. During the transportation course, it effects on the material which is made up of polar molecules. Microwave electromagnetic field can make these molecules polarize immediately. When microwave energy with the frequency of 2450 MHz is used for extraction, molecules within solute or solvent will do Polarity inversion movement in a speed of 2. 45 billion times/min, resulting in mutual friction and collision between Molecules. In this way, active parts of molecule (polarity part) are accelerated to be touched and reacted to each other greatly. And at the same time, a mass of heat energy is produced which can impel cell to break and make cell sap overflow and diffuse to solvent. When adopting solvent to extract effective components of Chinese herbal medicines, impregnation, percolation, reflux and continuous reflux extractions etc. Are used commonly. By principle, all of them can add microwave to process assistant extraction so as to be high-effective extraction of Chinese herbal medicines.

Based on the soluble property of different components within Chinese herbal medicines, solvent extraction method uses solvent, which has high solubility of active constituents and slight solubility of those components with no need to dissolve, to dissolve effective components out of medicinal organization.

Microwave high-frequency electromagnetic wave can penetrate through the medium of extraction into vascular bundle and glandular cell system within materials. Due to the absorption of microwave energy, internal temperature Of cells is increased quickly, which makes its internal pressure go beyond the expansion bearing capability of cell Walls, resulting in the break of cells. Effective components within cells flow out freely, are captured and dissolved by
Extraction medium in the condition of lower temperature. By the aid of further filtering and separation, required sub-Stance is extracted.

2. Advantages of Microwave-Assistant Extraction
(1) Traditional heat extraction adopts heat conduction and heat radiation etc. To transfer heat from outside to inside. However, microwave-assistant extraction adopts inside and outside heating at the same time. There is no high-temperature heat source and heat gradient is eliminated. So, it makes the extraction quality increased greatly, And effectively preserves the funct-ional components of foods, medicines and other chemical materials.
(2) As microwave can process heating by penetrating through the surface of materials, extraction time is greatly
Saved. According to many field data, general multi-functional extraction pot spends 8 hours completing work, while
Microwave dynamic extraction equipment with same size can finish work in only some dozens of minutes, saving 90% time.
(3) Microwave energy has supernormal extraction capability. As for the same materials, traditional method co-mpletes extraction after two or three times. In the condition of microwave, it can finish extraction only once. Process routine is simplified dramatically.
(4) There is no thermal inertia happened during microwave extraction; Easy to control. All of parameters can be digital display, which has been connected with pharmaceutical modernization.
(5) Microwave extraction has high purity. It can be widely applied, such as water extraction, alcohol extraction and fat extraction.
(6) Low extraction temperature, not easy to be burnt, easy separation, convenient after-treatment, and energy saving.
(7) Small usage of solvent (compared with traditional methods, it is reduced by 50%-90%).