The ingredients in herbal medicine are quite complex. They contain not only active ingredients, but also invalid ingredients. To improve the therapeutic effect of Chinese herbal medicine, it is necessary to extract its active ingredients. Extraction is directly related to the content of effective ingredients in finished products and their internal quality, the effect of jail bed and economic benefits.
At present, the common methods of extracting active ingredients of Chinese herbal medicines in actual production are impregnation (room temperature impregnation, warm impregnation, decoction), percolation, reflux and so on. The extraction time is long and the proposed rate is low. With the development of modern science and technology, ultrasound technology has been widely used in industry, agriculture, medicine and health and other fields. Because of the advantages of simple equipment, convenient operation, short extraction time, high extraction rate, energy saving, saving medicinal materials and no heating, the application of this method in extracting Chinese herbal medicines has attracted more and more attention. This paper reviews the application of ultrasound technology in the extraction of Chinese herbal medicines and the problems that should be paid attention to in the extraction process.
1. The Theoretical Basis of Extracting the Components of Chinese Herbal Medicine by Ultrasound Technology
Ultrasound is a kind of elastic mechanical vibration filter, which is a vibration outside the auditory threshold. It produces strong vibration, high speed, strong cavitation effect and stirring effect. Therefore, it can destroy the cells of plant medicinal materials and make the solvent permeate into the cells of medicinal materials, thus accelerating the dissolution of the active ingredients in the medicinal materials in the solvent, so as to improve the effectiveness. The extraction rate of components. At the same time, the structure of the active ingredients extracted by ultrasound was investigated by comparing the active ingredients proposed by conventional methods. According to the literature reports, the effective components obtained by the two methods were compared and analyzed by TLC, IR and NMR spectra. The results of the two methods were consistent, which showed that ultrasonic extraction would not change the structure of the effective components, shorten the extraction time and improve the extraction rate, so as to extract the components of Chinese herbal medicine. A new method of rapid and high yield is provided.
2. Application of Ultrasound Technology in the Extraction of Chinese Herbal Components
2.1 Saponins are extracted by water decoction or soaking in organic solvents, which takes a long time and has a low extraction rate. Ultrasound technology can shorten the extraction time and improve the extraction rate. Song Xiaomei et al. extracted the main effective component of Gynostemma pentaphyllum from Gynostemma pentaphyllum. The ultrasonic extraction of Gynostemma pentaphyllum saponins three times, 80 minutes each time, could significantly improve the yield of Gynostemma pentaphyllum saponins. Shao Jingli et al. extracted the dangshen saponins from Dangshen, compared with the conventional solvent impregnation method, and the Dangshen powder was treated by ultrasound for 40 minutes. After that, the extraction rate of Codonopsis saponins was more than 1 times higher than that of the conventional method (methanol cold impregnation for 48h), and the time was shortened by 98.6%. The crude product quantity of Codonopsis Saponins Extracted by ultrasound was nearly 2 times higher than that of the conventional method, and the purity was also higher. Some experts mentioned the main effective component of diosgenin from the roots and stems of Dioscorea nipponica, which was soaked in 70% ethanol for 48h as the control. The extraction rate of 20 kHz ultrasound for 30 minutes was 12 times higher than that of the control. The extraction rate of 1 MHz ultrasound for 30 minutes was 1.34 times higher than that of the control group. This process can save 23.4% of the medicinal materials. Therefore, ultrasonic extraction of saponins has the advantages of saving time, saving medicinal materials, less impurities and high extraction rate.
2.2 The extraction of alkaloids from Chinese herbal medicines by conventional extraction of alkaloids generally takes a long time and the yield is low, but after ultrasonic treatment, good results can be obtained. Berberine was extracted from Phellodendron amurense and soaked in saturated lime water for 24 hours as control. The extraction rate was 18.26% higher than that of the control group by 20 kHz ultrasound for 30 minutes, and the structure of berberine remained unchanged. Guo Xiaowu et al. extracted Berberine from rhizome of Coptis amurensis amurense. The experiment proved that the ultrasonic method was superior to the soaking method, i.e. the ultrasonic treatment of 20 kHz for 30 minutes. The proposed rate is as high as 8.12%. In the 1985 edition of Chinese Pharmacopoeia, the toxic components of Trichoderine (strychnine) and brucine were extracted by ultrasonography. It was clearly stipulated that when the drug content was determined, the toxic components were treated with ultrasonics for 40 minutes, equivalent to cold soaking for 24 hours. It can be seen that the extraction process of alkaloids by ultrasonic technology is simple, time-saving and high yield.
2.3 Flavonoids are extracted by water decoction, alkali extraction and acid precipitation or ethanol and methanol immersion, which is time-consuming, labor-consuming and low extraction rate. Ultrasound extraction can improve extraction rate and shorten extraction time. Baicalin was extracted from the rhizome of Scutellaria baicalensis. The extraction rate of baicalin was higher in 10 minutes with water as solvent than in 3 hours with water. The extraction rate of baicalin was higher in 40 minutes with 20 kHz ultrasound. Rutin was extracted from Sophora japonica L. by ultrasound for 40 minutes. The extraction rate was 22.53%, which was 1.7-2 times of the current large-scale production rate. The comparative test showed that 30-40% of the medicinal materials were saved and the economic benefit was high.
2.4 Extraction of anthraquinone derivatives in plants has complex forms. Free and bound forms often coexist in the same Chinese herbal medicine. Generally, ethanol or dilute alkaline aqueous solution is used to extract anthraquinone derivatives, which are destroyed by long-term heating and affect the proposed rate. Extraction of anthraquinones from rhubarb by ultrasound for 10 minutes is higher than that by Decoction for 3 hours. At the same time, extraction rate of anthraquinones by ultrasound at 20 kHz is higher. In the extraction process of compound Shouwu oral liquid, Polygonum multiflorum and rhubarb containing a large number of anthraquinone derivatives are extracted. The senna leaves were extracted by ultrasound to avoid the failure of anthraquinone glycosides to destroy the active ingredients due to long decoction.