Study On Extraction Of Isoflavones From Puerariae Lobata And It's Preparation For Microcapsules

Pueraria is a general term for the kudzu of leguminous plant or the blocky dry-root of the puerariae.The most important ingredient in pueraria lobata is puerarin isoflavones,and the content of isoflavones in kudzu is higher than other types of pueraria,so it is commonly used in chinese medicinal materials.Such as puerarin,daidzin,daidzein,puerarin-7-xyloside,etc.they not only have a good therapeutic effect on cardiovascular diseases,but also play roles in lowering blood pressure and affecting blood rheology as well as platelet aggregation which has been widely used in anti-cancer and myocardial protection.At present,the puerarin isoflavones in extracting solution of pueraria lobata are usually mixed together with the impurities by conventional physical and chemical methods,so it is difficult to achieve effective separation for them.Therefore,a microwave extraction method was conducted for the extraction experiments in this paper so that a higher purity and extraction rate of puerarin isoflavones from puerariae could be obtained.In the experimental implementation process,the extracted puerarin isoflavones was used as the core material so that the loss of biological activity caused by the structure and performance changes of the extracted puerarin isoflavones during long-term storage could be avoid,and the wall material which contained sodium alginate and chitosan wall material was mixed in a certain ratio to prepared a microcapsule to improve the storage stability and sustained the release of puerarin isoflavones.The specific research work of this paper is as follows:(1)Microwave-assisted extraction method was used to extract isoflavones from raw materials of pueraria lobata.The extraction rate was investigated from the influences of six factors of material-liquid ratio,extraction temperature,extraction time,ethanol concentration,microwave power and microwave treatment time for obtaining the optimal extraction parameters.The experimental results showed that the linear relationship of the rutin standard curve was y=6.3342x,where k=6.3342(Abs.mL/mg),and the correlation coefficient is R~2=0.9933.This reflected a proportional relationship between the isoflavone content and absorbance value in the extracted sample.According to the influence rules of different process conditions on the extraction rate,the optimal extraction parameters of puerarin can be achieved:the ratio of material to liquid was 1:8,the extraction temperature was 70°C,the extraction time was 120 min,the ethanol concentration was 80%,the microwave power was 300W,microwave treatment time was 5 min.Under the optimal extraction conditions,the content of isoflavones in pueraria lobata was 113.2 mg/g,and the extraction rate was 11.32%.(2)The sodium alginate was used as a wall material to embed the puerarin isoflavones,and the embedding rate was examined.First,the optimal test range for each factor was determined by univariate analysis method:calcium chloride concentration(1-5%),sodium alginate concentration(1-3%),chitosan concentration(0.5-2.5%),core wall ratio(1:2,2:3,1:1,3:2,2:1),reaction temperature(30-70°C)and magnetic stirring time(30-150min).Furthermore,the optimal preparation parameters of microcapsules by the response surface experiments were as follows:calcium chloride concentration was 2.91%,sodium alginate concentration was 2.57%,chitosan concentration was 1.39%,core-wall ratio was 0.96,reaction temperature was50°C,the magnetic stirring time was 120 min,and the embedding rate was 69.88%at this condition.Microcapsules were prepared under the optimal parameters and the morphology was characterized by scanning electron microscopy.The results of scanning electron microscopy showed that the prepared microcapsules had a good molding effect.(3)Pueraria isoflavone microcapsules prepared under optimal conditions were further studied to simulate the gastrointestinal fluid test,antioxidant activity test and storage stability test(temperature,light,oxygen,storage time).The results of scanning electron microscopy showed that the prepared microcapsules had a good molding effect.And the results of simulated gastrointestinal fluid test showed that the microcapsules had a good sustained release effect.After 7 h,the cumulative release of microcapsules in gastric juice reached 39.53%and that in intestinal fluid reached66.70%.The antioxidant activity test results showed that the antioxidant activity of puerarin was down-regulated after microencapsulation,which may be derived from the fact that the puerarin was not fully exposed during the measurement.This indicated that how to measure the anti-oxidation of pueraria lobata after microencapsulation was further needed to study.The results of storage stability test showed that the puerarin isoflavones and their microencapsulated products have good storage stability.