Investigation On The Extraction Of Pueraria Lobata At Low Temperature And It's Antioxidant Activity

Pueraria,as the anhydrous substance of tuberous root for wild Pueraria belonging to Pueraria lobate of leguminosae,is a kind of state-approved plant resource which can be applied as food and medicine.With isoflavone substances represented by puerarin as the major active ingredients,Pueraria can exert significant pharmacological effects,such as antineoplastic effect,anti-oxidation,vasodilation,treatment of cardiovascular disease,regulation of blood sugar level and reduction of blood fat.As a result,the content of puerarin can be regarded as the quality evaluation standard for products made of Pueraria extracts.China is abundant in Pueraria resources,most of which have been applied as the raw materials of food.Meanwhile,deficiencies existing in China's applications of Pueraria resources,such as small processing scale,poor technology and low additional value of products,have severely held back the development and applications of Pueraria resources.Therefore,the extraction technology of Pueraria was studied in this article and the in vitro antioxidant activity of Pueraria extracts was regarded as the quality standard to evaluate the product..Major research results are as follows:(1)The high performance liquid chromatograph of Dionex U3000 was adopted to inspect the content of puerarin and the chromatographic conditions were determined as:chromatographic column:Welch materials C18 chromatographic column(5?m,4.6×250nm);mobile phase:methyl alcohol:water = 25:75;detective wave length:250nm;flow velocity:1mL/min;sample size:20?L.Under such conditions,the sample can ensure a HPLC diagram featuring steady base line and superior resolution.By drawing the standard work curve for the content of puerarin,a equation of linear regression was figured out to represent the relations between the content of puerarin and integral value of peak area:Y=79.299X-0.3775(R2=0.9996,n=5).In case of the content of puerarin remaining within 1 and 15?g,it could maintain a proper linear relation with the integral value of peak area.(2)The influences of different cosolvents and their concentrations,extraction temperature,extraction time,number of extraction and solid-liquid ratio on the extraction ratio of puerarin was investigated by the single factor experiments,based on which the orthogonal experiment was carried out to achieve the optimal extraction technology in accordance with the extraction ratio of puerarin as the evaluation indicator.Results indicated that in cases where the solid-liquid ratio was 1:16,polyvinylpyrrolidone(PVP)cosolvent with a concentration of 45mg/mL was added and two times of extraction were conducted within 2.5 hours at the temperature of 60?,the extraction ratio of puerarin could achieve the maximum value up to 1.604 ±0.007%,higher than the extraction ratio of puerarin,which is 1.448 ±0.077%,using the traditional water extraction method at the temperature of 90?.(3)The oxidation method using Phenanthroline-Fe2+ was adopted to determine the ability of extracts to remove OH and auto-oxidation method relying on pyrogallic acid was applied to measure the ability of extracts to remove O2-·,which would help to evaluate the oxidation resistance property of extracts in a comprehensive way.At the temperature of 60?,the removal ratios of OH and O2-· were respectively 41.68 ±0.85%and 21.36±0.44%.While the removal ratios of OH and O2-·for two control groups of extraction at the temperature of 90? were respectively 25.57 ± 0.65%and 16.28 ± 1.00%,indicating that oxidation resistance property of low-temperature extract was significantly higher than that for high-temperature extract.(4)After multiple times of experiments and optimizations for vacuum freeze-drying conditions,the optimal pre-freezing condition was determined as:cool the materials to-35? and preserve the temperature for half an hour.Then the freeze-drying curve was drawn.After vacuum freeze-drying of extracts,the content of puerarin contained in the freeze-dried powder reached 13.37± 0.84%.Its removal ratios of ·OH and O2-= respectively achieved 63.58 ± 1.46%and 38.06± 0.89%.By applying PVP in the extraction technology of Pueraria,this study has optimized the traditional water extraction method,reduced the loss of puerarin in the process of extraction,and better preserved the oxidation resistance of Pueraria extracts.Meanwhile,it successfully obtained freeze-dried powder of Pueraria extracts featuring a higher content of puerarin and a more superior antioxidant activity by improving the freeze-drying conditions,providing a proper extraction and preservation proposal for the subsequent research and clinical applications for Pueraria extracts.Moreover,it has also served as another option for mass production of Pueraria extracts,which could minimize energy consumption of extraction and reduce the production loss.