Optimization of Microwave-assisted Extraction Technology of Polyphenols from Loropetalum chinense(R. Br.) Oliv

In order to optimize the microwave-assisted extraction technology of polyphenols from Loropetalum chinense （R. Br.） Oliv., the effects of microwave power, ethanol concentration, solid to liquid ratio and extraction time on polyphenols extraction rate were investigated. On the basis of single-factor test, a four-factor and three-level orthogonal test was designed by response surface method to establish a mathematical model between the response value and various factors. The results showed that the intensity of effect of different influencing factor on polyphenols ex- traction rate ranked as microwave power＇s〉solid to liquid ratio＇s〉extraction time＇s〉 ethanol concentration＇s. The optimum microwave-assisted extraction conditions for polyphenols from L. chinense were as follows： extraction power 254 W, ethanol concentration 60%, extraction time 12.5 rain and solid to liquid ratio 1：17. Under the optimum extraction conditions, the extraction rate of polyphenols from L. chinense was 19.17%.

Response surface optimization of microwave-assisted extraction for HPLC-fluorescence determination of puerarin and daidzein in Radix Puerariae thomsonii

Microwave-assisted extraction was optimized with response surface methodology for HPLC-fluorescence determination of puerarin and daidzein in Radix Puerariae thomsonii.The optimized extraction procedure was achieved by soaking the sample with 70% methanol（1∶15,v/v）for 30 min,and then microwave irradiation for 11 min at a power of 600 W.Coupling the extraction process with HPLC-fluorescence presented good recovery,satisfactory precision,and good linear relation.Compared with a method from the Chinese Pharmacopoeia,the proposed method enables higher extraction efficiency and more accurate analytical results.It can be of potential value in quality assessment of Radix Puerariae thomsonii medicinal materials.

Microwave-assisted Extraction of Isoflavones from Belamcanda chinensis

Microwave-assisted extraction （MAE） of isoflavones from Belamcanda chinensis was studied using ethanol as the solvent. The single factor experiment and the orthogonal method were used to optimize the MAE condition. It was concluded that two doses of intermittent microwave power radiation, 300 W each for 4 rain, were needed for extraction. The mass ratio of solvent to material was 8：1 and the alcohol mass fraction was 80%. The extracted liquor was then concentrated under vacuum and degreased with petroleum ether. The yield of total isofiavones was about 8.8% and the contents of tectoridin and iridin were 67.6% and 16.3% respectively. Compared with direct-heating extraction （DHE）, MAE may shorten extracting duration, reduce solvent consumption, and improve yield and purity of isoflavones from Belamcanda chinensis.

Microwave-assisted extraction of polysaccharides from solanum nigrum

The microwave-assisted method was used to extract polysaccharides from solanum nigrum. The optimum experimental parameters, mechanism of the extraction and the effect of microwave-assisted extraction process on the structures of polysaccharides were investigated. The extract was analyzed by the modified phenol-sulfuric acid method at 490nm. The optimum experimental parameters were obtained by orthogonal experiments as follows: extraction time 15min, microwave radiation power 455W and the process ratio of materials mass to solvent volume 1∶20. The results show that compared with the conventional reflux extraction, the microwave-assisted extraction has a higher yield in shorter time, with no effect on the finally obtained polysaccharides as seen from the FT-IR spectra. The scanning electron microscopy images reveal that the mechanism of the extraction is related to the structural changes of the plant cells in different extracting conditions.

Microwave-assisted extraction of Shenfu coal and its macromolecule structure

Coals consist of some molecules trapped within an organic matrix from which some organic compounds can be extracted by solvents. The Soxhlet technique has been widely used for extracting organic compounds. Microwave heating methods may be successfully applied in the field of coal science. Acetone extraction yields and the chemical composition of the extract were investigated using a typical Chinese coal, Shenfu coal, with microwave-assisted extraction. The acetone extract and residue were analyzed by GC/MS and carbon-13 nuclear magnetic resonance spectroscopy respectively. The carbon spectra were converted into several numerical parameters, fa, Ha, Xb, which indicate the difference in macromolecular structure between Shenfu coal and its residue. Furthermore, a hybrid genetic algorithm was employed using these parameters to approximate a coal macromolecule by assembling the structural fragments or functional groups into a large and complicated structure.

Microwave-assisted Extraction of Rutin and Quercetin from Flos Sophorae

Three microwave-assisted extraction(MAE) procedures were studied. The first procedure was household microwave oven dynamic extraction(HMODE). The second procedure was special microwave oven bath extraction(SMOBE). The third procedure was microwave resonant cavity dynamic extraction(MRCDE). The results obtained by the three microwave-assisted extraction procedures were compared with those obtained by using traditional Soxhlet extraction. The results indicate that the MAE not only took a shorter time, but also simplified the procedure, and made the extraction a higher yield. At the same time the results obtained by the three MAE procedures were also compared with each other.

Microwave-assisted Extraction of Effective Compounds from Traditional Chinese Herbal Medicine Ciwujia

Microwave-assisted extraction (MAE) for active ingredients in Ciwujia was studied by using ethanol as the extractant. Comparing MAE with conventional methods, the former can save the extracting time and increase the content of the active ingredients in product. As to the operation in MAE, the continuous radiation process is more convenient for the extraction for traditional Chinese medicine than the intermittent radiation process. Optimized by uniform design, MAE was proved to be an effective and novel process for extracting active ingredients in Ciwujia. The optimized MAE conditions are as follows: the microwave power is 510W, the radiation time 30min, the alcohol concentration at 80%, the ratio of solvent to solid material being 5:1, the soaking time 0.5h, and the herbal particle size is (520±19)μm.

Dynamic microwave-assisted extraction combined with liquid phase microextraction based on the solidification of a floating drop for the analysis of organochlorine pesticides in grains followed by GC

A convenient,cost-effective and fast method using dynamic microwave-assisted extraction and liquid phase microextraction based on the solidification of a floating drop was proposed to analyze organochlorine pesticides in grains including rice,maize and millet.Twelve samples can be processed simultaneously in the method.During the extraction process,10%acetonitrile-water solutions containing 110μL of n-hexadecane were used to extract organochlorine pesticides.Subsequently,1.0 g sodium chloride was placed in the extract,and then centrifuged and cooled.The n-hexadecane drops containing the analytes were solidifi ed and transferred for determination by gas chromatography-electron capture detector without any further filtration or cleaning process.Limits of detection for organochlorine pesticides were 0.97–1.01μg/kg and the RSDs were in the range of 2.6%–8.5%.The developed technology has succeeded in analyzing six real grains samples and the recoveries of the organochlorine pesticides were 72.2%–94.3%.Compared with the published extraction methods,the developed method was used to analyze organochlorine pesticides in grains,being more environmentally friendly,which is suitable for the daily determination of organochlorine pesticides.

Optimization of the microwave-assisted extraction of phlorotannins from Saccharina japonica Aresch and evaluation of the inhibitory effects of phlorotannin-containing extracts on HepG2 cancer cells

The use of a microwave-assisted extraction （MAE） method for the extraction ofphlorotannins from Saccharinajaponica Aresch （S.japonica） has been evaluated with particular emphasis on the influential parameters, including the ethanol concentration, solid/liquid ratio, extraction time, extraction temperature, and microwave power. The MAE procedure was optimized using single-factor design and orthogonal array design （OAD）. The content of total phlorotannins in S. japonica was determined using a Folin-Ciocalteu （FC） assay. A maximum total phlorotannin content of 0.644 mg of phloroglucinol equivalent per gram of dry weight plant （mg PGE/g DW） was obtained using the optimized model, which included an ethanol concentration of 55%, solid/liquid ratio of 1：8, extraction time of 25 min, irradiation power of 400 W, and temperature of 60~C. Under similar conditions, the application of a conventional extraction method led to a lower phlorotarmin yield of 0.585 mg PGE/g WD. These results demonstrated that the MAE approach provided better results for the extraction ofphlorotarmins from S.japonica and was a promising technique for the extraction of phenolic compounds from S. japonica and other materials. In addition, screening tests for the inhibitory activity showed that the phlorotannin-containing extracts significantly inhibited the growth of human hepatocellular carcinoma cells （HepG2） by inducing their apoptosis. The morphological changes that occurred during cell apoptosis were characterized using Hoechst33258 staining.

Application and research advancement on the microwave-assisted extraction

This paper summarized application and research advancement of the microwave-assisted extraction in the agriculture, food industry, environmental analytical chemistry, traditional Chinese medicine industry, and so on. The microwave-assisted extraction was manifested to be a simple device, wide area of application, high extraction efficiency, good reproducibility and low consumption of agent and time as well as low environmental pollution. At present, industrialization question of the microwave-assisted extraction technology has been attached importance, which will impel the microwave-assisted extraction technology to more development in the future

Study on chromatographic fingerprint of sarcandra glabra (Thunb.) by microwave-assisted extraction coupled to HPLC/DAD

Microwave-assisted extraction(MAE)was used for extraction of effective components of sarcandra glabra(Thunb.),and then chromatographic fingerprint of sarcandra glabra(Thunb.)was studied by high performance liquid chromatography/diode array detector(HPLC/DAD).The conditions of MAE were optimized by an orthogonal experiment,and then the authentication and validation of the chromatographic fingerprint were conducted.Nine peaks were identified as common peaks in the fingerprint chromatograms,and isofraxidin was considered as a reference compound and quantified.Relative standard deviations of retention time and peak area of each component were less than 3% and 8%,respectively.Similarity and difference analysis were conducted by use of PCA and relation coefficient.Twenty batches of sarcandra glabra(Thunb.)samples from two different producing areas could be classified into two different groups in the PCA model.The results showed that MAE-HPLC/DAD method was simple,efficient and stable for the study of complex chromatographic fingerprint of sarcandra glabra(Thunb.),which could provide more reliable and precise information for quality evaluation.

Assessment of Triazine Herbicides in Soil by Microwave-assisted Extraction Followed by Gas Chromatography Coupled to Mass Spectrometry Detection

An alternative and fast method for the analysis of a mixture of nine triazines herbicides in soil is presented. The method is based on MAE （microwave-assisted extraction） of herbicides using ethyl acetate as extractant. The economy in the use of solvents coupled with the decrease in extraction time and lower power consumption make MAE a technique that meets the principles of green chemistry. MAE operational parameters, extraction time, mass of the sample and extraction temperature, were optimized by RSM （response surface methodology）. Determination of analytes was completed using gas chromatograph coupled to mass spectrometry detection. The selected triazines could be efficiently extracted by the solvent at 80 ℃ for 10 min, with 80% output of maximum power. When the optimized method was applied to analysis samples, the recoveries of analytes ranged from 81.8 to 106.0% and relative standard deviations were lower than 8.41%. The method is stable and reasonable, which can be used for the determination of ninetriazine herbicides residues in soil.

MICROWAVE-ASSISTED EXTRACTION OF GLYCYRRHIZIC ACID FROM LICORICE ROOT-EFFECT OF THE PROPERTY OF SOLUTION ON EXTRACTION OF GA

The property of extraction solution is an important factor influencing the extraction efficiency. In the present work, the effect of the property of solution on extraction of GA was studied, which including the concentration of ethanol, ammonia and cation (M+), pH of extraction solution, different kinds of organic solvent etc. The results show that 50%-60%(v/v) ethanol can reach high percentage extraction of GA. If 1% (v/v) ammonia solution was added into 60%(v/v) ethanol, the percentage extraction can be increased from 2.0% to 2.31%. Without ammonia, 50mmol/L [M+] (M+ = K+, NH4+) was added into 60%(v/v) ethanol, percentage extraction of GA can reach about 2.26%. If pH of solution (60% ethanol) was adjust to pH=4.0, it can reach high percentage extraction. If pH of solution (60% ethanol + 50mmol [M+], pH=6.1) was adjust tO PH=4.0, especially M+ is K+ or NH4+, it can reach almost same extraction efficiency as that of 1% ammonia solution + 60% ethanol, and the operation environment can be greatly improved.

Optimization of microwave-assisted extraction of bioactive alkaloids from lotus plumule using response surface methodology

In this work,a fast and efficient microwave-assisted extraction(MAE) method was developed to extract main bioactive alkaloids from lotus plumue.To optimize MAE conditions,three main factors were selected using univariate approach experiments,and then central composite design(CCD).The optimal extraction conditions were as follows:methanol concentration of 65%,microwave power of 200 W,and extraction time of 260 s.A high performance liquid chromatography–diode array detector(HPLC–DAD) method was established to quantitatively analyze these phytochemicals in different lotus plumule samples and in different part of lotus.Chromatographic separation was carried out on an Agilent Zorbax Extend-C_(18) column(4.6 mm×150 mm,3.5 μm).Gradient elution was applied with the mobile phase constituted with 0.1% triethylamine in water(A)and acetonitrile(B):40%-70% B at 0-8 min,70%-100% B at 8–9 min,100% B for 2 min,and then equilibrated with 40% B for 2 min.

Comparison of Response Surface Methodology and Artificial Neural Network in Predicting the Microwave-Assisted Extraction Procedure to Determine Zinc in Fish Muscles

In this paper, the estimation capacities of the response surface methodology (RSM) and artificial neural network (ANN), in a microwave-assisted extraction method to determine the amount of zinc in fish samples were investigated. The experiments were carried out based on a 3-level, 4-variable Box–Behnken design. The amount of zinc was considered as a function of four independent variables, namely irradiation power, irradiation time, nitric acid concentration, and temperature. The RSM results showed the quadratic polynomial model can be used to describe the relationship between the various factors and the response. Using the ANN analysis, the optimal configuration of the ANN model was found to be 4-10-1. After predicting the model using RSM and ANN, two methodologies were then compared for their predictive capabilities. The results showed that the ANN model is much more accurate in prediction as compared to the RSM.

Kinetic Mechanisms for Preparing Silymarin via Microwave-assisted Extraction

The kinetic mechanism for the preparation of silymarin from milk thistle seeds was studied during the microwave-assisted extraction （MAE） process. The results showed that the transfer rate of silymarin from milk thistle seeds increased with the microwave output power and temperature during MAE processing. The apparent extraction rate constant k （s-1） was 1.2028×10-2 , 1.2248×10-2 , and 1.2485×10-2 , and diffusion coefficient D （m2·s-1 ） was 4.21×10-10, 4.29×10-10 , and 4.37×10-10 at the microwave temperatures of 383, 393, and 403 K, respectively, in the silymarin MAE process. With the help of scanning electron microscopy （SEM）, the microstructures of the samples extracted by MAE were observed. The results revealed that the increased efficiency and rate of MAE of silymarin could be attributed mainly to the subsequent cell change resulting from superheating effects during MAE.

Study on microwave-assisted extraction of coal

The effect of different factors on coal extraction yield-temperature, solvent, coal type and irradiation time were investigated for different China coals under microwave-assisted extraction（MAE）. The results show that the optimum temperature for ethanol, acetone and THF are 393,373 and 373 K respectively and the extraction yield of THF is higher than that of other two solvents under MAE. Extraction with several single organic solvents were conducted for the 5 typical China coals-Shenfu, Tongchuan, Panzhihua, Yitai and Huating coal under microwave-assisted extraction and Soxhlet extraction. Results indicat that extraction yield of ethylenediamine, ethanol, acetone, tetrahydrofuran under MAE are all higher than that of Soxhlet extraction and MAE required less time. Tongchuan coal extracts of ethanol and acetone which were extracted by MAE and Soxhlet extraction were analyzed by GC/MS.

Evaluating the performances of accelerated-solvent extraction, microwave-assisted extraction, and ultrasonic-assisted extraction for determining PCBs, HCHs and DDTs in sediments

Three extraction techniques have been recently used for the quantitative extraction of semi-volatile organic pollutants in sediments, i.e. accelerated solvent extraction （ASE）, microwave assisted extraction （MAE） and ultrasonic assisted extraction （UAE）. However, their extraction efficiencies have rarely been quantitatively compared using rigorous mathematical methods. In this paper, one-way analysis of variance （ANOVA） was employed to evaluate the performance of ASE, MAE and UAE in the overall extraction of PCBs, DDTs and HCHs by analysis of their recoveries from the Standard Reference Material IAEA-417, a sediment sample certified by many international laboratories. Conclusions were drawn at a significance level of P〈 0.05. No significant differences were found among the mean values for method recoveries using ASE, MAE and UAE. The mean values for real recoveries using ASE and MAE were nearly identical, but the real recovery using UAE was much lower. The concentrations of all PCBs, DDTs and HCHs except for CB52 and o,p＇-DDT using UAE were the lowest. Comparing the results obtained using ASE with MAE, the concentrations of CB28, CB52, CB138, ct-HCH, [3-HCH, p,p＇-DDE and p,p＇-DDD were nearly identical, while the concentrations of other compounds were significantly different. Based on the low recoveries, it was concluded that UAE is a relatively inefficient extraction method, while ASE and MAE are equivalent methods. Taking into consideration the relative standard deviation （RSD） values, solvent volume, extraction time, and purchasing costs of the apparatus, MAE was considered superior to ASE for extraction of PCBs, DDTs and HCHs.

Rapid Lab-Scale Microwave-Assisted Extraction and Analysis of Anthropogenic Organic Chemicals in River Sediments

An Ethos EZ Microwave Lab Station is employed in the development of a robust and efficient microwave extraction method for organic contaminants of anthropogenic origin in river sediments. The extraction method is designed for a small, representative set of target compounds encompassing a range of physicochemical properties. Listed in order of gas chromatography elution they are para-cresol, indole, 4-tert-octylphenol, phenanthrene, triclosan, bisphenol-A, carbamazepine, and benzo [a] pyrene. The sediments samples are extracted wet, which reduces preparation time, and allows the ambient moisture of the sediments to aid in microwave energy absorption and the extraction process. The microwave can hold up to 12 samples that can be simultaneously extracted allowing for rapid sample preparation. Utilizing the pressurized vessels, microwave energy, and a unique mixture of three organic solvents allows for multiple samples to be extracted rapidly with minimal solvent consumption. The final extracts are quantified by gas chromatography/mass spectrometry. Recoveries of the 8 target compounds in sediment range from 49% to 113%, and method detection limits range between 14 and 114 μg kg–1, which are comparable with other more time consuming methods.