Dynamic Microwave-assisted Extraction of Flavonoids from Radix Scutellariae

IntroductionRadix Scutellariaeis the root ofScutellaria bai-calensis Georgi(Labiatae), which is widely cultivatedand used as traditional Chinese medicine. It has beendemonstrated to be anti-inflammatory, anti-metamor-phic, antiviral, anti-hot, and live pr…     

中药刺五加叶中有效成分的几种微波辅助提取方法研究

利用高压微波提取法、常压回流微波提取法、流动微波提取法和索氏提取法提取中药刺五加中黄酮和皂苷类化合物,考察各种提取方法提取效率随时间的变化。结果表明,高压微波提取法在压力为300kPa,完全提取的时间为10min;常压回流微波提取法完全提取的时间为14min;流动微波提取法完全提取的时间为10min;索氏提取法需8h尚能完成。各种提取方法总黄酮的提取率分别为43．7、48．2、42．7和34．7mg／g;总皂苷的提取效率分别为60．2、61．5、59．8和46．5mg/g。与索氏提取法比较,微波提取法提取黄酮和皂苷,提取时间大大缩短,且提取效率显著提高。     

Microwave Accelerated Extraction and Capillary Electrophoresis Analysis of Berberine from the Cortices of Phellodendron Wilsonii and Phellodendron Amurense

Berberine is one of the most important bioactive compounds used in Chinese herbal drugs to evaluate the quality of the Phellodendron cortex. The cortices of Phellodendron wilsonii and Phellodendron amurense, extracted by using a microwave‐assisted process under a domestic microwave oven in methanol solvent and analyzed by capillary electrophoresis with the buffer solution of 82% 0.1 M aqueous sodium acetate and 18% MeOH (v/v), were demonstrated to be higher in extracting berberine contents and shorter in the process time than those extracted by using a reflux extraction in methanol solvent (for sample B, 2.27 ± 0.08% in 3 min vs. 1.92 ± 0.14% in 5 hrs, respectively). Therefore, the microwave‐assisted process for extraction of berberine is more efficient, rapid and convenient than the reflux extraction and can be used for the extraction of bioactive substances from the crude Chinese drugs.     

Extraction and determination of bioactive flavonoids from Abelmoschus manihot (Linn.) Medicus flowers using deep eutectic solvents coupled with high‐performance liquid chromatography

A highly efficient and ecofriendly extraction method using deep eutectic solvents was developed to extract bioactive flavonoids from Abelmoschus manihot (Linn.) Medicus flowers. First, a series of deep eutectic solvents using choline chloride as hydrogen bond acceptor with different hydrogen bond donors was successfully synthesized. Then, the types of deep eutectic solvents and the extraction conditions for bioactive flavonoids (hyperoside, isoquercitrin, and myricetin) were optimized based on the flavonoids extraction efficiencies. The optimized deep eutectic solvent for hyperoside and isoquercitrin extraction was composed of choline chloride and acetic acid with a molar ratio of 1:2. The optimized deep eutectic solvent for myricetin extraction was composed of one mole of choline chloride and two moles of methacrylic acid. The optimal extraction conditions were set as: solid to solvent ratio, 35:1 (mg/mL); extraction time, 30 min; extraction temperature, 30°C. Qualitative and quantitative analysis were performed using ultra high performance liquid chromatography with tandem mass spectrometry and high‐performance liquid chromatography. And the extraction efficiencies of hyperoside, isoquercitrin, and myricetin under optimal extraction conditions were calculated as 11.57, 5.64, and 1.11 mg/g, much higher than those extracted by traditional extraction solvents. Therefore, the prepared deep eutectic solvents can be selected as alternative solvent to extract bioactive flavonoids.     

微波辅助提取刺五加中黄酮类化合物过程中的化学变化研究

利用HPLC-UV和HPLC-ESI-MSn技术系统地研究了传统中药刺五加中黄酮类化合物在微波辅助常压和高压提取过程中的化学变化, 并考察了提取压力和提取时间对其化学变化规律的影响, 结果表明, 在提取压力超过300 kPa时芦丁开始失去一个芸香糖转化为槲皮素; 随着微波照射时间的延长, 金丝桃苷、芦丁、槲皮苷和槲皮素提取产率先增加, 而后下降. 提取压力越大, 提取速率越快, 分解的速度也越快,达到最高提取产率的时间越短.     

Calligonum polygonoides Linnaeus Extract: HPLC‐EC and Total Antioxidant Capacity Evaluation

Flavonoids in Calligonum polygonoides Linnaeus extract were separated, detected, and identified by reverse‐phase high‐performance liquid chromatography (RP‐HPLC) with electrochemical detection (EC) in combined isocratic and gradient elution using a glassy carbon or a boron doped diamond electrode. Ultrasonication coupled with a microwave‐assisted technique was developed to optimize the extraction of the phenolic compounds. The total antioxidant capacity was quantified using the DPPH^. method and voltammetry. The RP‐HPLC‐EC led to the detection of nine different flavonoids: catechin, delphinidin, fisetin, myricetin, epicatechin, kuromanin, rutin, callistephin and procyanidin A2, in a single run by direct injection of the sample extract solution.     

Non-polar Solvent Microwave-Assisted Extraction of Volatile Constituents from Dried Zingiber Officinale Rosc.

A new method, non-polar solvent microwave-assisted extraction （NPSMAE）, was applied to the extraction of essential oil from Zingiber officinale Rosc. in closed-vessel system. By adding microwave absorption mediumcarbonyl iron powders （CIP） into extraction system, the essential oil was extracted by the non-polar solvent （ether） which can be heated by CIP. The constituents of essential oil obtained by NPSMAE were comparable with those obtained by hydrodistillation （HD） by GC-MS analysis, which indicates that NPSMAE is a feasible way to extract essential oil from dried plant materials. The NPSMAE took much less extraction time （5 min） than HD （180 min）, and its extraction efficiency was much higher than that of conventional polar solvent microwave-assisted extraction （PSMAE） and mixed solvent microwave-assisted extraction （MSMAE）. It can be a good alternative for the extraction of volatile constituents from dried plant samples.     

Molecular imprinted polymer for solid‐phase extraction of flavonol aglycones from Moringa oleifera extracts

Molecular imprinted polymer produced using quercetin as the imprinting compound was applied for the extraction of flavonol aglycones (quercetin and kaempferol) from Moringa oleifera methanolic extracts obtained using heated reflux extraction method. Identification and quantification of these flavonols in the Moringa extracts was achieved using high performance liquid chromatography with ultra violet detection. Breakthrough volume and retention capacity of molecular imprinted polymer SPE was investigated using a mixture of myricetin, quercetin and kaempferol. The calculated theoretical number of plates was found to be 14, 50 and 8 for myricetin, quercetin and kaempferol, respectively. Calculated adsorption capacities were 2.0, 3.4 and 3.7 μmol/g for myricetin, quercetin and kaempferol, respectively. No myricetin was observed in Moringa methanol extracts. Recoveries of quercetin and kaempferol from Moringa methanol extracts of leaves and flowers ranged from 77 to 85% and 75 to 86%, respectively, demonstrating the feasibility of using the developed molecularly imprinted SPE method for quantitative clean‐up of both of these flavonoids. Using heated reflux extraction combined with molecularly imprinted SPE, quercetin concentrations of 975 ± 58 and 845 ± 32 mg/kg were determined in Moringa leaves and flowers, respectively. However, the concentrations of kaempferol found in leaves and flowers were 2100 ± 176 and 2802 ± 157 mg/kg, respectively.     

Nonaqueous capillary electrophoretic separation of polyphenolic compounds in wine using coated capillaries at high pH in methanol

Nonaqueous capillary electrophoretic separation of a group of flavonoids (quercetin, myricetin, catechin, epicatechin) and resveratrol in wine was investigated in methanol at high pH. Malonate background electrolyte (pH* 13.5, ionic strength I = 14.2 mmol/L) provided highly repeatable separations of the analytes. Tests of untreated and coated (poly(glycidylmethacrylate-co-N-vinylpyrrolidone)) capillaries showed the analysis to be faster (6.5 min vs. 25 min) and the repeatability better in the coated capillaries. The coating procedure was simple and highly repeatable and the coating was stable during 40-45 runs. Determination of the last migrating peaks (epicatechin, resveratrol and catechin) was achieved merely by evaporating the wine samples and reconstituting the residue in methanol. For determination of the first migrating peaks (quercetin and myricetin) the samples were submitted to solid-phase extraction in C8 cartridges.     

响应面法优化板栗花总黄酮微波提取工艺

应用响应面法优化了乙醇微波提取板栗花中总黄酮的工艺条件。用光度法在波长510 nm处测定提取液中总黄酮的含量(以芦丁为标准),从而判断提取条件的优劣。经试验确定最优提取条件为:①微波功率700 W;②提取时间80 s;③提取溶剂乙醇与水的体积比为40比60;④板栗花料与提取溶剂的比值为1比100。在此选定条件下板栗花总黄酮的提取率达到(3.47±0.14)g/100 g,与理论值(3.49 g/100 g)很接近。     

Digestion of biological materials using the microwave-assisted sample combustion technique

In this study a procedure for sample digestion based on sample combustion assisted by microwave radiation is proposed. Combustion is started by microwave radiation in the presence of oxygen under pressure using ammonium nitrate as aid for ignition. The system was adapted in a microwave oven with quartz closed vessels. A quartz piece is used simultaneously as a sample holder and as protection to the cap of quartz vessel from the flame generated in the combustion process. Sample was pressed into a pellet and placed on a disc paper in the holder and 50 μl of 50% m/v ammonium nitrate solution was added. The influence of the absorption solution (diluted and concentrated nitric acid or water) on the recoveries for Cu and Zn was evaluated. About 3 s of microwave irradiation was necessary to start the combustion. The combustion process was evaluated in relation to the influence of sample mass on the ignition time, combustion time and maximum operation pressure. Bovine liver, milk powder and oyster tissue certified reference materials were used to evaluate the accuracy of the procedure for determination of copper and zinc. Good agreement for zinc (96% to 103%) was obtained from bovine liver certified reference material when microwave combustion and microwave combustion followed by reflux were used to sample decomposition, even if water was used for absorption of analyte. For copper, the combustion followed by reflux of 5 min allows an agreement from 96% to 100%. Similar results were obtained for oyster tissue samples. However, for milk powder good agreement close to 100% was obtained only if 4 mol l^− 1 HNO₃ was used with a reflux step. Results from the proposed procedure were also compared to those from conventionally used procedures for biological samples decomposition, such as wet digestion in open vessels and microwave-assisted digestion in closed vessels. The advantages of this procedure include the complete sample decomposition in less time than other procedures and the acid consumption was always lower than 2%. Another advantage is the low residual carbon content, less of 1.4% without reflux and less than 0.3% with the reflux step and the possibility of use of diluted acid as absorbing solution. Moreover, the new holder allows an effective protection of the vessel cap to burnt high masses.     

Ionic liquid aqueous solvent-based microwave-assisted hydrolysis for the extraction and HPLC determination of myricetin and quercetin from Myrica rubra leaves

An ionic liquid aqueous solvent‐based microwave‐assisted hydrolysis (ILAS‐MAH) approach was proposed for the rapid extraction and accurate determination of myricetin and quercetin from Myrica rubra (M. rubra) leaves for the first time. The effects of the ionic liquid class and concentration, liquid–solid ratio, hydrolysis temperature and time were investigated to obtain the optimal ILAS‐MAH conditions. The optimized conditions were 2.0 mol/L [bmin][HSO4] or 2.5 mol/L acidified [bmin]Br solution, liquid–solid ratio 30:1 (mL : g), hydrolysis temperature 70°C and hydrolysis time 10 min. Under these conditions, the recoveries of myricetin and quercetin were in the range of 86.3–107.3% with relative standard deviation lower than 5.8%. Compared with conventional heating hydrolysis and regular MAH, the proposed approach reduced hydrolysis time and improved yields. The mechanism of ILAS‐MAH was also investigated. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization of Extraction Conditions for Flavonoid Composition and Antioxidant Activity of Radix Scutellariae

Microwave, ultrasonic, and reflux extraction were compared to provide an optimized method for flavonoids from Radix Scutellariae including the antioxidant activity of the extracts. The antioxidant activities of the extracts were evaluated by 2,2-diphenyl-1-picrylhydrazyl and oxygen radical absorbance capacity assays. Baicalin, wogonoside, baicalein, wogonin, and oroxylin A were quantified using ultra-high performance liquid chromatography. For microwave extraction, with a ten minutes treatment, the extraction efficiencies of the analytes were higher than treatments by refluxing for 180 minutes and sonication for sixty minutes. In addition, the antioxidant activity of the microwave extracts was slightly higher than the extracts obtained by the other methods. Microwave extraction conditions were further optimized by a single-factor experiment and the optimum conditions were 50 percent ethanol–water (volume by volume), an extraction temperature of 100 degrees celsius, an extraction time of ten minutes, and a sample to solvent ratio of 1:50. This study combines extraction, phytochemistry, and bioactivity to screen the most efficient extraction procedure for flavonoids from Radix Scutellariae.     

Negative-pressure cavitation extraction for the determination of flavonoids in pigeon pea leaves by liquid chromatography-tandem mass spectrometry

A new method, namely negative-pressure cavitation extraction (NPCE), followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) is presented for the extraction and quantification of flavonoids in pigeon pea leaves. This method combines the high efficiency of NPCE and the sensitivity and accuracy of MS/MS. The influential parameters of the NPCE procedure including liquid/solid ratio, extraction time, nitrogen flow and number of extraction cycles were optimized. Under optimized conditions, the efficiency of NPCE for extracting five flavonoids was compared to microwave-assisted extraction (MAE), ultrasonic extraction (USE) and heating reflux extraction (HRE). Additionally, structural disruption to pigeon pea leaves samples with different extraction methods was investigated by scanning electron microscopy. The relative recovery with NPCE was equivalent to or higher than that with USE and obviously higher than those with MAE and HRE which are usually conducted in higher temperatures. Furthermore, because NPCE was performed with nitrogen at room temperature, the degradation and oxidation of analytes were avoided. In addition, the NPCE method was validated in terms of repeatability and reproducibility, relative standard deviation for relative recovery was lower than 5.84 and 8.83%, respectively. The method was also successfully applied for the quantification of five flavonoids in pigeon pea leaves. All these results suggest that the developed NPCE-LC–MS/MS method represents an excellent alternative for the extraction and quantification of flavonoids in other plant materials.     

Continuous determination of total flavonoids in Platycladus orientalis (L.) Franco by dynamic microwave-assisted extraction coupled with on-line derivatization and ultraviolet-visible detection

This paper describes a new method for the determination of total flavonoids in Platycladus orientalis (L.) Franco. The method was based on dynamic microwave-assisted extraction (DMAE) coupled with on-line derivatization and ultraviolet-visible (UV-vis) detection. The influence of the experimental conditions was tested. Maximum extraction yield was achieved using 80% aqueous methanol of extraction solvent; 80 W of microwave output power; 5 min of extraction time; 1.0 mL min⁻¹ of extraction solvent flow rate. The derivatization reaction between aluminium chloride and flavonoid is one of the most sensitive and selective reactions for total flavonoids determination. The optimized derivatization conditions are as follows: derivatization reagent 1.5% aluminium chloride methanol solution; reaction coil length 100 cm; derivatization reagent flow rate 1.5 mL min⁻¹. The detection and quantification limits obtained are 0.28 and 0.92 mg g⁻¹, respectively. The intra-day and inter-day precisions (R.S.D.) obtained are 1.5% and 4.6%, respectively. Mean recovery is 98.5%. This method was successfully applied to the determination of total flavonoids in P. orientalis (L.) Franco and compared with heat reflux extraction. The results showed that the higher extraction yield of total flavonoids was obtained by DMAE with shorter extraction time (5 min) and small quantity of extraction solvent (5 mL).     

Microwave assisted extraction of soy isoflavones

A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30-70% in water and water), temperatures (50-150 °C), extraction solvent volume, as well as the sample size (1.0-0.1 g) and extraction time (5-30 min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5 g of sample, 50 °C, 20 min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).     

Application of ionic liquid‐based surfactants in the microwave‐assisted extraction for the determination of four main phloroglucinols from Dryopteris fragrans

An ionic liquid‐based surfactant combined with microwave‐assisted extraction method, followed by RP‐HPLC‐diode array detection (DAD) with a core shell column, was successfully applied in extracting and quantifying four major phloroglucinols from Dryopteris fragrans. Eight ionic liquids with different cation and anion were investigated, and 1‐octyl‐3‐methylimidazolium bromide presented the best relative extraction efficiency for four phloroglucinols. The optimum conditions of this method were as follows: ionic liquid concentration 0.75 M, liquid/solid ratio 12:1 mL/g, extraction time 7 min, extraction temperature 50°C, and irradiation power 600 W. The quality analytical parameters of the method were obtained based on the linearity, precision, accuracy, detection, and quantification limits. The recoveries were between 96.90 and 103.5% with standard deviations not higher than 4.7%. Compared with ionic liquid‐based heat reflux extraction, ultrasonic‐assisted extraction, negative‐pressure cavitation extraction, and conventional microwave‐assisted extraction, the relative extraction efficiencies of the proposed method for four phloroglucinols increased 1.5–40.4%. The method was successfully applied for the quantification of four major phloroglucinols from D. fragrans. All these results suggest that the developed method represents an excellent alternative for the extraction and quantification of phloroglucinols in other plant materials.     

Design of guanidinium ionic liquid based microwave‐assisted extraction for the efficient extraction of Praeruptorin A from Radix peucedani

A series of novel tetramethylguanidinium ionic liquids and hexaalkylguanidinium ionic liquids have been synthesized based on 1,1,3,3‐tetramethylguanidine. The structures of the ionic liquids were confirmed by ¹H NMR spectroscopy and mass spectrometry. A green guanidinium ionic liquid based microwave‐assisted extraction method has been developed with these guanidinium ionic liquids for the effective extraction of Praeruptorin A from Radix peucedani. After extraction, reversed‐phase high‐performance liquid chromatography with UV detection was employed for the analysis of Praeruptorin A. Several significant operating parameters were systematically optimized by single‐factor and L₉ (3⁴) orthogonal array experiments. The amount of Praeruptorin A extracted by [1,1,3,3‐tetramethylguanidine]CH₂CH(OH)COOH is the highest, reaching 11.05 ± 0.13 mg/g. Guanidinium ionic liquid based microwave‐assisted extraction presents unique advantages in Praeruptorin A extraction compared with guanidinium ionic liquid based maceration extraction, guanidinium ionic liquid based heat reflux extraction and guanidinium ionic liquid based ultrasound‐assisted extraction. The precision, stability, and repeatability of the process were investigated. The mechanisms of guanidinium ionic liquid based microwave‐assisted extraction were researched by scanning electron microscopy and IR spectroscopy. All the results show that guanidinium ionic liquid based microwave‐assisted extraction has a huge potential in the extraction of bioactive compounds from complex samples.     

改进的微波辅助无溶剂法提取薄荷和陈皮中的挥发油组分

An improved solvent free microwave extraction, in which a kind of microwave absorption medium （carbonyl iron powder） was used, was applied to the extraction of essential oil from dried menthol mint and orange peel without addition of any solvent and pretreatment. It took much less time of extraction （30 min） than microwave-assisted hydrodistillation （90 min） and conventional hydrodistillation （180 min）. The kinds of chemical compositions in essential oil extracted by different methods were almost the same and such improved solvent free microwave extraction can be a feasible way in extraction of essential oil from dried plant materials.     

Development of microwave assisted extraction for the simultaneous determination of isoflavonoids and saponins in radix astragali by high performance liquid chromatography

A microwave assisted extraction (MAE) procedure was first developed for the simultaneous determination of isoflavonoids and astragalosides in Radix Astragali (RA). MAE showed the highest extraction efficiency when compared to Soxhlet, reflux, and ultrasonic extraction. It was found that flavonoid glycoside malonates were converted into their related glycosides during the prolonged conventional extraction, thus affecting the reproducibility. However, the conversion was inhibited when using MAE. After being optimized in terms of solvents, microwave power, and irradiation time, MAE was used for the simultaneous determination of isoflavonoids and astragalosides in RA with HPLC-UV-evaporative light scattering detection (ELSD). Our results indicated that extraction by MAE was more effective than by other conventional techniques. Moreover, the MAE method followed by HPLC-UV-ELSD determination was a simple, rapid, and reliable method for the quality assessment of RA.