Microwave-assisted Extraction And Purification Of Pueraria Isoflavonoids

Radix Puerariae is dried root of Pueraria. Pueraria lobata (Willd.) Ohwi and Pueraria thomsonii Benth are two most commen Pueraria. Radix Puerariae contains a variety of useful isoflavonoids, including Puerarin, Daidzein, Daidzin, Purearia-xyloside, etc.These isoflavonoids have been shown to be useful for the treatment of alcohol abuse, dysentery, cancers and cardiovascular diseases in pharmacological and clinical study. The extract of Radix Puerariae obtained by traditional method contains lots of impurities and purification is an individual step after extraction. This thesis focuses on integrating extraction and purification into one step. Once the method is developed, the operating process will be much simpler and both the yield and purity will be higher. The detail work can be concluded as follows:(1)An efficient microwave-assisted aqueous two-phase extraction technique is developed to extract and enrich isoflavonoids from Radix Puerariae simultaneously. The effects of the concentrations of K2HPO4 and ethanol, solid-liquid ratio, extraction temperature, extraction time and microwave power are investigated. In addition, the response surface methodology is used to optimize the extraction of isoflavonoids from Radix Puerariae. The optimized conditions are obtained as 24.89%(w/w) K2HPO4, 29.49%(w/w) absolute alcohol, extraction temperature 80 ℃, extraction time 8 min, and microwave irradiation power 500 W. Under the optimal condition, the extraction yields of isoflavonoids reaches to 133.8 mg/g. The recovery of isoflavonoids is 94.6%, and the yield of puerarin is 49.5 mg/g. Compared with microwave assisted extraction, microwave-assisted aqueous two-phase extraction method integrates extraction, concentration and purification into one process. It is a potential method in extracting and purifying effective constituent from herb medicines.(2)The kinetics and thermodynamics of adsorbing isoflavonoids from aqueous solution and ionic liquid solution by HPD-100 resin is investigated. The absorption isotherm is fitted with Langmuir and Freundlich isotherm adsorption equations respectively. The results indicate that adsorption process obeys Freundlich isotherm model (R2>0.992) other than Langmuir model, that is, the adsorption is polymolecular layer adsorption of uneven surface. Thermodynamic parameters are calculated and the negative ΔH shows that the adsorption was exothermic. When the initial concentration of isoflavonoids is low, the negative ΔHvalues indicate that the adsorption is a spontaneous process and low temperature is benefit to adsorption. Negative ΔS shows that the randomness of the system becomes lower after adsorption. The kinetic experimental data are also fitted by pseudo-first order and second order model and the result shows that pseudo-second order model are more sutable for the adsorption of the isoflavonoids on HPD-100 resin (R2>0.99).The kinetic process of four kinds of resins(S-8、AB-8、HPD-100 and polyamide resin) are compared. All of them follow pseudo-second order and HPD-100 has the biggest adsorption capacities. Besides that, resins with isoflavonoids on them are eluted by 80% (v:v) ethanol and nearly all the isoflavonoids can be eluted from HPD-100. Thus, HPD-100 resins will be used as adsorbent in dynamic extracting-adsorbing experiment.(3)Dynamic microwave-assisted ionic liquid extracting-adsorbing isoflavonoids method is developed. In the dynamic microwave-assisted system, isoflavonoids extracted will be soon adsorbed on HPD-100,ionic liquid solution as effective extractant can be reused in a circuit system. Extracting condition is optimized by single-factor experiment as follows:extracting temperature is 50℃, mass of HPD-100 resins is 1.0 g, extracting time is 60 min, flow rate is 1 mL/min, ionic liquid concentration is 0.4 mol/L and the volume of extractant is 20 mL, elutant is 80%(v:v) ethanol. In this condition, the yield of Puerarin and Daidzin reaches to 42.52 mg/g and 9.35 mg/g. This method not only purifies and concentrates isoflavonoids in extracting process, but also realizes the reuse of ionic liquid.