| Herba Houttuyniae are the whole plant of Houttuynia of Houttuynia genus from Saururaceae. The main components include organic oil, flavonoids, polysaccharides, alkaloids, etc. Its functions mainly are relieving dysuria, removing toxie, and diseharging pus. It's widely used as traditional medicine and food, and it is designated as a drug-diet herb by the Ministry of Health. This study mainly researches the technique of extraction and purification, structure and antioxidant activities of polysaccharide from Houttuynia cordata Thunb. Which has important theoretical value and practical significance to develop more functional food and deep-processing ways of Houttuynia Cordata Thunb. The main contents and results are as follows.(1) The optimization of extraction technology from Houttuynia cordata Thunb leaves. For the first, it tests the polysaccharides content in roots, stems and leaves by phenol-sulfuric acid method, and the contents are 23.43%, 25.15% and 28.21%, and reach a conclusion is that the highest part of polysaccharides is Houttuynia cordata Thunb leaves. Then, the study use the enzymatic method to extract the polysaccharides from Houttuynia cordata Thunb leaves, and the response surface methodology(RSM) is used to build the regression equation model to optimize the extraction process of enzymatic method. The polysaccharides yield as the index, and investigates the effects of cellulose concentration, liquid-to-solid ratio, extraction temperature and extraction time on the yield of polysaccharides. Subsequently, the order of factors that effects the polysaccharides yield is: liquid-to-solid ratio>cellulose concentration>extraction time > extraction temperature. The optimal extraction condition is 0.9% cellulose at 31 ? for 174 min in a liquid-to-solid ratio of 52:1. Under this condition, the measured values of polysaccharides yield is 32.95 mg/g. The optimized extraction condition are applied for stems and roots of Houttuynia cordata Thunb.(2) Isolation and purification of polysaccharides from Houttuynia Cordata Thunb. Firstly, the protein removal rate as the index to carry on the comparative experiment, result shows that the effect of combination of enzyme method and Sevage method is better than Sevage method. When the extraction times is five, the protein removal rate is 83.4% and polysaccharides retention rate is 63.56%. Next, the Resin Static Adsorption method is used to decoloring from polysaccharides. Firstly, using five kinds of resin(AB-8, D-201, X-5, LSA-10, D-101) to compare with decolorization effect, and get the comprehensive score by the rate of decolorization and the retention rate of polysaccharide to determine an optimal resin that is D-101, it need to screen out the best decolorization process of D-101 resin. Through the single element experiment and orthogonal experiment, optimal decolorization condition of D-101 resin is that temperature is 45 ?, p H value is 5.5 and time is 2h. Under this condition, decolorization rate is 89.56%, retention rate of polysaccharides is 87.72%, comprehensive score is 88.64%. Final using 80% grade alcohol to make the polysaccharides subsided, and get high concentration of pure polysaccharide. This method also can be used for the separation and purification of other parts from Houttuynia Cordata Thunb.(3) Comparative study on the antioxidant capacity of polysaccharides in roots, stems and leaves from Houttuynia Cordata Thunb. The peroxide value as the index to study the antioxidant effect of polysaccharides on lard by Schaal oven method. Meanwhile, the antioxidant capacity of polysaccharides also are evaluated by the savenging abilities of DPPH and ABTS free radical. The results in the range of experimental concentration showes that polysaccharides have certain antioxidant effect on lard. The antioxidant effect strengthened with increasing of the polysaccharides concentration. The ability of scavenging free radical is directly proportional to the polysaccharides concentration. When the polysacchaarides concentration is from 0.05 mg/m L to 0.2 mg/m L, the removal rate of DPPH free radical is from the lowest 15.61% to the highest 90.53%, as well as the removal rate of ABTS free radical is from the lowest 9.67% to the highest 81.45%. Besides, at the same concentration, according to the total of antioxidant capacity of polysaccharides from Houttuynia cordata Thunb, the order from strong to weak is that leaf> stem > root.(4)The physic-chemical properties analysis of polysaccharides from Houttuynia cordata Thunb including structural group, appearance characteristics, stability. Polysaccharides from Houttuynia cordata Thunb are analyzed by synchronous thermal analyzer, scanning electron microscopy and infrared spectrometer. The results indicate that polysaccharides begin to degrade at 190 ? and stop degrading at 630 ?, which indicates favorable thermal stability of polysaccharides. Scanning electron microscopy shows that internal structure of polysaccharides have loose shape and the surface is a bit rough. At last, the infrared spectrometer indicates that polysaccharides contain the characteristic groups. |
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