Microwave extraction technology in medicine, natural products Extraction
Extraction, namely microwave-assisted extraction (MAE), is based on the ability of different substances absorb microwave makes the difference matrix material extraction system in certain areas or certain components are selectively heated , so that the extracted material from the substrate or system is separated into a smaller dielectric constant , the relative difference in absorption of microwave extraction agent , to achieve the purpose of extraction .
1 , the mechanism of microwave extraction
Microwave is a frequency 300MHZ to 300GHZ between electromagnetic waves, which are volatile, high resistance, thermal and non-thermal properties of the four basic characteristics . The microwave frequency used is 2450MHZ. Microwave heating the material is heated using the polar molecules ( such as H2O, CH2Cl2 , etc. ) in the microwave electromagnetic field and the orientation of the fast steering arrangement , resulting in tearing and friction and heat . Conventional heating method of the heat transfer equation is: heat → → sample vessels , and thus has been constrained energy transfer efficiency . Microwave heating is energy directly acting on the material is heated , its pattern is: heat → Sample → vessels . Air and containers for microwave essentially no absorption and reflection , which fundamentally ensures rapid energy conduction and fully utilized.
2 , the characteristics of microwave extraction
① selectively reflected in the microwave , polar molecules because of the selective heating to its selective dissolution .
② MAE greatly reduce the extraction time and improve the extraction rate , the traditional method requires a few hours to 10 hours , ultrasonic extraction also need half an hour to one hour , microwave extraction just a few seconds to a few minutes , the extraction rate increased to dozens hundreds of times , even thousands of times .
③ microwave extraction solvent due to the low affinity of the limits , the choice of solvent is more, while reducing the amount of solvent . In addition , microwave extraction if used for large-scale production , the safe, reliable, non-polluting, is the green engineering, production lines is simple, and can save investment .
Microwave extraction generally applicable to the thermal stability of the material, heat-sensitive substances, microwave heating easily cause them to degeneration or inactivation ; requires materials with good water absorption , otherwise difficult to absorb sufficient microwave cell itself can break , releasing the product will be difficult out ; microwave extraction selectivity for components .
3 , the application of microwave extraction
Microwave extraction is widely used in glycosides , flavonoids , post category , polysaccharides, alkaloids and other components extracted .
Ganzler other extracts from lupine seeds cytisine ( Siba Ding ) , with shaking extraction method is more traditional , microwave extract Siba Ding content is 20% higher than the shaking method , and fast , solvent consumption are greatly reduced .
Brachet A like from the cocoa leaf extract cocaine and benzoyl ecgonine , investigated the extraction solvent , particle size, sample humidity, microwave power and irradiation time and other parameters. Extract obtained with the traditional method are equivalent, but only 30 seconds when .
Some scholars microwave technology Ephedrine leaching effects compared with conventional boiling microwave extraction methods the pros and cons , the results of microwave extraction method was significantly better than ephedrine boiling method, and half the amount of ephedra extract coarse significantly better than the full amount of ephedra Pieces, and Chinese medicine theory "cook scattered half" match. Another scholar microwave extraction of berberine berberine berberine dry solids and assay results as an indicator to compare two methods of microwave and reflux . Dry solids measurement results show that microwave treatment in unit time has obvious advantages compared to reflux extraction ; to berberine content as an indicator , the results showed reflux extraction berberine content higher than microwave extraction .
Hao Shou Zhu and other studies of microwave technology for rhubarb anthraquinone leaching effects , orthogonal experiment of microwave output power , material particle size , leaching time three factors on the extraction rate , preferably optimum leaching solution . Out of the microwave extraction of preferred programs and conventional boiling method and ethanol reflux method , the results of particle size on the leaching of anthraquinone ingredients very significant effect , a significant effect on the leaching power , have a certain influence on the leaching time . Microwave extraction method rhubarb anthraquinone extraction rate was significantly better than conventional boiling method , with ethanol reflux fairly .
Shen Lan , etc. to rhubarb , cassia different polarities anthraquinones as an index component orthogonal design extraction rate were investigated , the results show microwave extraction for rhubarb , cassia seed extract selectively different polar components is not obvious and the same temperature conditions, emodin rhubarb roots , rhubarb , physcion extraction rate was significantly higher than that in Cassia seeds extraction rate of the same composition .
Liu Chuanbin such as a microwave broken cells combined with solvent extraction method to extract Rhodiola callus Salidroside . After 1 minutes the herbs after microwave treatment , the water extraction at room temperature for 10 minutes, can be fully extracted Salidroside , compared with traditional methods , the former has a short time , without heating , the extract impurities and so on. Duan Rui , also use this method to extract flavonoids in Ginkgo biloba . Microwave for 5 minutes and then 70% ethanol extracted for 1 hour to obtain the extract flavonoids than not treated with microwave above 18.8% , paper chromatography showed that the use of microwave temperatures, flavonoids nature does not change. Li Rong , also studied by this method flavonide extraction process , also get a more satisfactory result. In addition, Yanyu Xiao and other extracts from ginger antioxidants and found that the first five minutes with a microwave , flavonoids extraction rate has improved significantly.
Guo libraries for baicalin Scutellaria microwave extraction were studied using Orthogonal Design The optimum is 70% microwave power ( maximum power of 850 watts ) with 35 % ethanol as solvent, solvent 30 times the amount of pressure 0.15Mpa , constant time of 30 seconds to get a better yield than the ultrasonic method was nearly 10%. Zhang Mengjun other with uniform design of microwave extraction of flavonoids optimum conditions: liquid ratio 1/8, ethanol concentration 78% , microwave power 388 W, extraction time 1 minute. Microwave extraction rate (24.6mg/ml) significantly better than water extraction (11.4mg/ml).
Chen Bindeng study Pueraria different microwave extraction of total flavonoids , with 77% ethanol, solid-liquid ratio of 1/ 14 , lower than 60 ℃ condition, microwave intermittent treatment three times , total flavonoids extraction rate of 95% , compared with traditional compared to the thermal extraction , not only high yield, and fast , energy-saving .
Wang silk and other applications of microwave extraction of total flavonoids from Pueraria lobata , puerarin, results showed that the extraction efficiency increases , the extraction time was shortened , the active ingredient , the yield increased significantly.
Studies have found that using microwave extraction polyphyllins , the result of the effect of microwave treatment for 5 minutes that basically reached two hours conventional heating effect, and fewer impurities , microwave extraction 10 minutes that saponin has extracted completed.
⑤ organic acids
Guo library applications such as self-designed with higher precision pressure control special microwave sample preparation system for the active ingredient in honeysuckle chlorogenic acid and chlorogenic acids extraction conditions were investigated and compared with ultrasonic extraction , the extraction rate ratio ultrasonic high near 2 percent.
Guo Jintang applications such as microwave extraction glycyrrhizin , 8 minutes can be obtained with continuous reflux extraction three hours equivalent results .
Shihezi University School of Medicine workers in the microwave extraction of polysaccharides made ??a lot of research work , the extraction of plants, including licorice, pokeweed , Cistanche, Rhodiola , Rhodiola leaf , Astragalus, Codonopsis and so on. They MCL-3 a microwave reactor , with a certain amount of petroleum ether, ethyl ether and 80% ethanol extraction for 20 minutes in a microwave oven and then the residue extracted with water polysaccharide content determined after 20 minutes , the results were higher than the conventional extraction methods , extraction time is reduced by about 12 times .
Tangke Hua and other polysaccharides Ficus microwave extraction , microwave extraction Ficus initially recognized at 80 ℃ polysaccharide should be alkaline medium combined with microwave pretreatment obtain higher extraction rate . According to Liu and other processed Radix microwave , boiling water and then extracted IRPS , assay results showed that the yield of polysaccharides reached 33.062% , 75.211% mass fraction better than alone decoction method . Microwave extraction was also used tea polysaccharide , combined with alcohol precipitation prepared tea polysaccharide yield 2.52% , UV and IR spectroscopy confirmed that the process on the chemical structure of tea polysaccharide products had no effect .
Still others use the microwave extraction of soybean oligosaccharides , yield than non- microwave conditions significantly improved dissolution time is much shorter , just 6 minutes .
⑦ volatile oil
Currently, there are already many foreign scholars began using microwave extraction of volatile oil. Environment Canada Pare in 1991 applied for a U.S. patent on natural products , including mint , parsley, cedar leaf and garlic , etc., using the microwave transparent ( hexane, etc. ) , or partially transparent ( methanol , methylene chloride , etc. ) solvents.
Patents in the extraction process and requirements set forth as follows: ① material is crushed , extracts should be able to absorb microwave radiation ; ② material into transparent or partially transparent to microwave extraction agent ; ③ with a certain frequency microwave radiation extraction ; ④ separation extracts ; ⑤ extract recovered or directly used ( if not separated ) . Extract analysis showed that in terms of microwave than traditional steam distillation : extraction rate , quality of extract , extraction time , the cost , and operation procedures . Another foreign literature , using microwave extraction technique savory, fennel, Achyranthes grass , thyme leaves and sage genus of essential oils.
Chinese scholars are also more volatile oil extracted by microwave , Shihezi University School of Medicine MODERN APPLIED others from rugosa, Quebec tarragon leaves, Xinjiang Codonopsis, Xinjiang cumin fruits , flowers, stems and leaves of Rhodiola using micro Botticelli was volatile oil , results than steam distillation extraction rate and with time is short.
In addition there are Pelargonium and volatile oil Litsea microwave extraction were reported.
Currently , microwave extraction technique used in addition to the above major components , the number of additional components, such as steroids, terpenes , vegetable oils, flavors , coloring extract has also been reported . Such as : use this method to extract gossypol from cottonseed , is extracted from the beans beans pyrimidine glucoside , cytisine and other natural compounds , extraction efficiency is much higher than Soxhlet extraction and ultrasonic method, but also consume less solvent , time is short . Han Wei and other microwave-assisted extraction, extraction of artemisinin research compared with the traditional extraction method , the extraction rate has significantly improved .