| Astragalus is a genus astragalus of perennial herbs. Astragalus is roots of astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao and astragalus membranaceus (Fisch.) Bge. And it has been used as a traditional medicine. Doctors of Chinese traditional medicine have applied it in kinds of diseases with the other different herbs. Modern pharmacology studies show that astragalus has many functions, such as blood pressure-reduction, diuretic anti-aging, blood pressure-lowering, tumor-fighting, antiviral, assuaging, analgesia, and so on. All these functions are relative with the active ingredients, including polysaccharides, saponin, flavonoidin in astragalus. At present, the traditional extraction method is water-boiled--filtration--concentrated by evaporation--adding ethanol--separated by a centrifugal machine--product-refined. The application of nanofiltration concentration taken place of evaporation concentration in the astragalus extraction solution was studied on the paper. The nanofiltration concentration method has been a new separation technology. The MWCO between 200-1 000 can be separated with nanofiltration membrane. And in this separation process, there have merits of no phase change, high separation effective, easy to operate and avoiding heat damage at room temperature. Not only is the process energy saving and lower production costs, but it will not disrupt biological activity.The orthogonal experiments guided by yields of the polysaccharides and total saponinn was designed to determine the optimum extraction conditions, which was decocting 60 minutes each time with 7 times amount of water for 2 times. Repeat experiment indicated that the choosed technics was scientific and economical and can be used to medicament production and clinic application.Cellulose enzyme was added during the extraction of astragalus and the aqueous extracts were concentrated by nanofiltration and thermal evaporation respectively. The results of ethanol precipitation were analyzed and compared. Three nanofiltration membrane of MWCO 200 was characterized by measuring the permeation flux, and the retention coefficient of glucose and NaCl at different applied pressures to choose the best membrane subassembly. The experimental results show that on concentration by nanofiltration membrane, the permeation flux, elimination of water and the measure retention coefficient of were measured at different applied pressures and the characteristics of nanofiltration process were discussed. The retention properties of polysaccharides for astragalus extract solutions with different concentrations were measured. The average retention properties of polysaccharides was 99.6% show that nanofiltration can be applied in the concentration of astragalus extract solutions. Compared with the traditional thermal concentration, under the same extract condition, those concentration by nanofiltration had less polysaccharides, better quality but higher content. Under the same concentration condition, those adding cellulose enzyme had higher yield of polysaccharides, but lower content.Under the optimum extraction conditions determined by orthogonal experiments, astragalus was decocted. The aqueous extracts were concentrated by nanofiltration and thermal evaporation respectively. Subsequently the concentrated solutions were precipitated by adding ethanol and then were separated by a centrifugal machine. The contents of astragalus polysaccharides, total saponin and total flavonoid in the yields were analyzed and compared. The average retentions of the astragalus polysaccharides, total saponin and total flavonoid by nanofiltration membrane are 99.9%, 98.7% and100%. Contrasted with traditional thermal concentration, the astragalus polysaccharides, total saponin and total flavonoid with Nanofiltration concentration were almost the same yield, higher content, and more white. Compare the expenses of two concentration method, the main operation expenses of eaporation concentration is steam, and that of nanofiltration concentration is membrane subassembly. The expenses of nanofiltration concentration is 1/5～1/6 of eaporation concentration.
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