Microwave-assisted Water Extraction Research Articles

Optimizing Microwave-Assisted Extraction from Levisticum officinale WDJ Koch Roots Using Pareto Optimal Solutions

The current research trend is not only focused on advanced techniques to intensify the extraction of bioactive compounds from plants, but also on the optimization process. The objective of this work was the implementation of the multiple criteria analysis using navigation on Pareto sets to determine the optimal parameters for the microwave-assisted extraction of Levisticum officinale WDJ Koch roots in order to obtain the maximum efficiency of the antioxidant potential of the extracts. The optimized parameters were extraction time, microwave power, and plant biomass/solvent ratio, while the evaluation criteria were based on the total phenols, flavonoids, reducing sugars, and antioxidant capacity. It was shown that the process parameters analyzed, i.e., biomass/solvent ratio, process time, and microwave power, determined the extraction efficiency of total phenolic content (TPC). A different observation was made for the analysis of total flavonoid content (TFC) and total antioxidant potential (TAA). Compared to the assessment of TFC and TAA, a completely different trend was observed for the analysis of total reducing sugars (RSC). Sets of Pareto optimal, compromise, and preferred solutions were identified that will maximize the efficiency of the extraction of bioactive compounds from biomass. Due to the determined number of Pareto optimal solutions, an approach related to the introduction of preferences in the optimization procedure was applied. It was shown that for a satisfactory level of bioactive compounds, extraction should be carried out at a maximum microwave power of 750 W. Preferred solutions were obtained for root biomass to water ratios ranging from 0.0536 g/mL to 0.0679 g/mL. The preferred optimal time for microwave-assisted water extraction ranged from 64.2857 to 85.7143 s.

Structural characterization and antioxidant activity of polysaccharides extracted from Porphyra haitanensis by different methods

This study was to investigate the structure and antioxidant activity of Porphyra haitanensis polysaccharides (PHPs) extracted by different methods, including water extraction (PHP), ultra-high pressure (UHP-PHP), ultrasonic (US-PHP) and microwave assisted water extraction (M-PHP). Compared with water extraction, the total sugar, sulfate and uronic acid contents of PHPs was enhanced by ultra-high pressure, ultrasonic and microwave assisted treatments, especially those of UHP-PHP were increased by 24.35 %, 12.84 % and 27.51 %, respectively (p < 0.05). Meanwhile, these assisted treatments affected the monosaccharide ratio of polysaccharides and significantly reduced the protein content, molecular weight as well as particle size of PHPs (p < 0.05), and resulted in a loose microstructure with more porosity and fragments. PHP, UHP-PHP, US-PHP, and M-PHP all possessed in vitro antioxidant capacity. Among them, UHP-PHP had the strongest oxygen radical absorbance capacity, DPPH and ·OH radicals scavenging capacities, which increased by 48.46 %, 116.24 %, and 14.98 % respectively. Moreover, PHPs particularly UHP-PHP effectively increased the cell viability and reduced ROS levels of H2O2 induced RAW264.7 cells (p < 0.05), indicating their good effects against cell oxidative damage. The findings suggested that PHPs with ultra-high pressure assisted treatments has the better potential to develop natural antioxidant.

Extraction, Composition and Comparisons–Free Volatile Compounds from Hydrosols of Nine Veronica Taxa

The extraction of bioactive plant components, which belong to specialized metabolites, is carried out by conventional and novel extraction methods. In this study, a classical (hydrodistillation, HD) and a novel technique (microwave-assisted water extraction, MAE) were used to isolate free volatile compounds from nine Croatian Veronica taxa (family Plantaginaceae). Each of these extracts consists of a lipophilic phase and an aqueous phase (hydrosol). Gas chromatography-mass spectrometry was used to identify the compounds in the hydrosol phase studied taxa Veronica. The compounds β-ionone and benzene acetaldehyde were detected in all nine Veronica hydrosols studied. Other compounds abundant in all investigated species are germacrene D, α-muurolol, (E)-β-damascenone, and β-ionone. Also, the compositions of hydrosols and lipophilic phases (published in our previous research) of these nine Veronica species were compared. Identification of the compounds in both extract parts is important for selecting the extract part for further biological research. According to the distribution of species in the PCA analyses comparing two methods, only two species showed a greater difference in the composition of the hydrosol by the two methods, therefore our conclusion is that for most species there is no significant difference in the composition. Microwave water extraction is a better choice with regards to more environmentally friendly working conditions. Furthermore, we conclude that hydrosol extracts are not waste products, but are a valuable source of compounds with great potential applications.

Optimization of Microwave-Assisted Water Extraction to Obtain High Value-Added Compounds from Exhausted Olive Pomace in a Biorefinery Context.

Microwave-assisted water extraction (MAWE) was evaluated to obtain the valuable bioactive compounds hydroxytyrosol and mannitol from exhausted olive pomace (EOP). The influence of the operational parameters solid loading (3–15%, w/v), temperature (40–100 °C), and extraction time (4–40 min) was studied using an experimental design. The optimized conditions maximizing their joint extraction were 12% w/v solid loading, 100 °C temperature, and 16 min. It was possible to solubilize 5.87 mg of hydroxytyrosol/g EOP and 46.70 mg mannitol/g EOP. The extracts were also further characterized by liquid chromatography–mass spectrometry, which detected other hydroxytyrosol derivatives such as oleacein, verbascoside, and oleuropein. Moreover, the applied MAWE conditions promoted the co-extraction of proteinaceus material, which was also evaluated. In order to carry out an integral valorization of this waste, the extracted EOP solid was further evaluated chemically and microscopically before recovering the bioactive triterpenes. In particular, maslinic acid and oleanolic acid were obtained, 9.54 mg/g extracted solid and 3.60 mg/g extracted solid, respectively. Overall, MAWE can be applied as a first stage in the fractionation of EOP to support its valorization in a biorefinery framework.

Microwave-Assisted Water Extraction of Aspen (Populus tremula) and Pine (Pinus sylvestris L.) Barks as a Tool for Their Valorization.

The barks of aspen (Populus tremula) and pine (Pinus sylvestris) are byproducts of wood processing, characterized by their low economic value. In the present study, microwave-assisted one-cycle water extraction was explored as a tool for the valorization of this biomass as a source of biologically active compounds. The microwave extractor of the original construction equipped with a pressurized extraction chamber and a condenser section was used. The microwave-assisted extraction (MAE), specially including dynamic dielectric heating up to 70 °C followed by 30 min of isothermal heating, promoted the isolation of salicin from aspen bark, allowing for the obtention of a two-times-higher free salicin concentration in water extracts (−14% vs. 7%) reached by multi-cycle accelerated solvent extraction (ASE), which is an advanced technique used as a reference. The MAE of pine bark with dynamic heating up to 90–130 °C, avoiding the isothermal heating step, allowed for the obtention of a 1.7-times-higher concentration of proantocyanidin dimers-tetramers, a 1.3-times-higher concentration of catechin and a 1.2-times-higher concentration of quinic acid in water extracts in comparison to a more time- and solvent-consuming ASE performed at the same temperature. The biological activity of the obtained extracts was characterized in terms of their ability to inhibit xahntine oxidase enzyme, which is a validated target for the therapeutic treatment of hyperuricemia.

The microwave assisted extraction sway on the features of antioxidant compounds and gelling biopolymers from Mastocarpus stellatus

Microwave assisted water extraction of hybrid carrageenan and antioxidant compounds from Mastocarpus stellatus red alga was first proposed to recover biopolymers with specific rheological properties, saving time, avoiding chemicals and enhancing extraction yields when compared with conventional treatments. The hybrid carrageenans, precipitated from the liquid fractions recovered after microwave assisted water extraction were analyzed by Fourier transform infrared attenuated total reflectance, high-performance size-exclusion chromatography and rheology. The corresponding soluble extracts were also characterized by total phenolic content, antioxidant capacity, proteins, sulfate and carbohydrate content. The highest phenolic, antioxidant capacity and sulfate content were observed at 190 °C, without notable effect of heating time between 3 and 6 min. In contrast, a clear impact of both microwave heating temperature and time on the molecular weight distribution of hybrid carrageenans as well as on the viscoelastic behavior of formulated hydrogels was identified, being the strongest hydrogels achieved at 170 °C for 6 min. It should be highlighted that all proposed hydrogels exhibited stable mechanical properties in the absence of syneresis for a month of cold storage, except those made with biopolymers obtained with the mildest extraction conditions (3 min at 70 °C).

Application of Tea Extract in Food Industry

Background and Objectives: Tea is considered one of the most consumed drinks around the world and the health benefits of it have recently attracted the attention of different researchers. It has also been proven beneficial in preventing the danger of some diseases like cancer and cardiovascular problems. Further, lipid oxidation is one of the major problems in food products. Considering the above-mentioned issues, the present review focused on various techniques used to extract polyphenols from different kinds of tea, as well as their use in the food industry. Results and Conclusion: Based on our findings in this review, the main components of tea are polyphenols that have health benefits and include catechins, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, gallic acid, flavonoids, flavonols, and theophlavins. From these components, catechin is regarded as the most beneficial component. Many techniques have been discovered and reformed to extract tea compounds such as solvent-based extraction, microwave-assisted water extraction, and ultrasound-assisted extraction techniques. Overall, the microwave-assisted water extraction method is a useful method for extracting tea polyphenols, which may be used in the meat, oil, and dairy industries.

Intensified aqueous-based processes to obtain bioactive extracts from Plantago major and Plantago lanceolata

Subcritical water extraction (SWE) and microwave-assisted water extraction (MAE) have been investigated for the effective recovery of antioxidant compounds from Plantago major and Plantago lanceolata. Subcritical water extractions were carried out at several temperatures ranging from 25 to 200°C and two different extraction procedures have been used: individual and sequential extractions. For comparison purposes, microwave-assisted water extraction was carried out at the same extraction temperatures. The Plantago species’ extracts were characterized in terms of total phenol content by using the Folin-Ciocalteu assay. Antioxidant activity was measured using two different in vitro assays, namely DPPH radical scavenging and TEAC (trolox equivalents antioxidant capacity). The identification of bioactive components was carried out using liquid chromatography coupled to diode array and mass spectrometry (HPLC-DAD-MS). Results indicate the presence of various polyphenolic compounds such as plantamajoside, verbascoside and isoverbascoside and demonstrate that the extraction temperature had a positive influence on both extraction yield and antioxidant activity of the attained extracts. SWE and MAE demonstrated its usefulness as green extraction methods compared to traditional protocols and thus can be successfully employed to obtain bioactive extracts from Plantago species for their use in cosmetic and food industries.

Microwave assisted water extraction of plant compounds

AbstractThe development of environmentally friendly processes with limited generation of polluting streams to attain sustainable utilization of raw materials is encouraged. The implementation of novel extraction technologies more efficient, selective and with lower energy consumption than conventional ones, can help in achieving this objective. Particularly promising are aqueous based methods, since water is a cheap, safe and abundant solvent and the limited use of toxic organic solvents is a consumer's, ecological and processing demand. The benefits and the limiting aspects of microwave assisted water extraction, either adding water as the only solvent or in solvent free processes, using the naturally present water in vegetal materials for the extraction of valuable components from renewable vegetal sources are highlighted and the potential of this technique for industrial applications is discussed. © 2014 Society of Chemical Industry

Determination of Five Arsenic Species in Porphyra by Microwave-Assisted Water Extraction and High Performance Liquid Chromatography–Atomic Fluorescence Spectrometry

Arsenic (As) speciation in edible seaweed has received a considerable research interest due to its impact on the food safety and human health. In this paper, we developed a simple and cost-effective methodology to extract, separate, and analyze As species in Porphyra samples collected from Jiangsu, Zhejiang, and Shandong provinces of China. Four extraction methods were compared in terms of extraction efficiency and resolution of As species. Microwave-assisted water extraction was chosen due to its short time (5 min) and high efficiency (93% of total As extracted). Total As concentration in the Porphyra samples varied within 14.0–42.1 µg g−1, determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) after acid digestion. Five As species were determined by high performance liquid chromatography—ultraviolet photo-oxidation—hydride generation—atomic fluorescence spectrometry (HPLC–(UV)–HG–AFS). DMA was found only in one sample with the concentration of 0.67 µg g−1. No As(III), As(V), MMA, and AsB were detected. Taken together, the As speciation results suggest that the risk associated with As in Porphyra to human health may be negligible.

Comparison of subcritical water extraction and microwave-assisted water extraction for the determination of chlorophenols in polluted lake sediments

Two environmentally friendly sample preparation methods, subcritical water extraction (SWE) and microwave-assisted water extraction (MAWE) coupled to the gas chromatography with electron capture detector (GC-ECD), were evaluated and optimized for the sensitive, selective and solvent-free determination of four chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 4-chlorophenol and pentachlorophenol) in polluted Ya-Er Lake sediments. An orthogonal array design L9 (33) was applied to select the optimum conditions for SWE. The best results as regards sensitivity, repeatability and analyte recovery were obtained using SWE with 9 mL of sodium hydroxide solution (pH 9), at 150 °C for 80 min. The best extraction conditions for MAWE were obtained by using the same extractant as SWE at 900 W and 0.2 MPa for 6 min. Under final working conditions, satisfactory recoveries of individual chlorophenols (CPs) were obtained in the range of 77.7–113.0% and 83.5–104.7% for SWE and MAWE respectively. The effectiveness of the extraction conditions proposed in both methods was evaluated for the extraction of 2,4-DCP in lake sediments with different sample characteristics such as organic carbon and water content. The results indicated that sediments containing relatively low amounts of organic carbon can be quantitatively extracted by both extraction methods. For sediments with larger amounts of organic carbon, the MAWE-based method showed a little better result for analyte recovery than SWE.

Composition and bioactivity of tea flower polysaccharides obtained by different methods

The effects of different extraction methods on the composition and bioactivity of tea flower polysaccharides (TFPS) were investigated. Traditional water extraction (TWE), microwave-assisted water extraction (MAE), and ultrasound-assisted water extraction (UAE) were compared to extract TFPS. TWE was found to be the optimal method with highest yield of TFPS and highest neutral and acid saccharides contents in TFPS. TFPS obtained by TWE mainly consisted of two kinds of polysaccharides with the molecular weight of 31 kDa and 5000 Da. TFPS obtained by MAE and UAE generally had very low inhibitory effects on α-glucosidase. TFPS (2 mg/mL) obtained by TWE exhibited a strong inhibitory effect on α-glucosidase with the inhibitory rate of 83.3%. TFPS obtained by TWE had stronger proliferation effect on lymphocyte at the concentration of 3.0 μg/mL than that of tea leave polysaccharides (TPS).

Microwave‐assisted water extraction of green tea polyphenols

Green tea, a popular drink with beneficial health properties, is a rich source of specific flavanols (polyphenols). There is a special interest in the water extraction of green tea polyphenols since the composition of the corresponding extracts is expected to reflect the one of green tea infusions consumed worldwide. To develop a microwave-assisted water extraction (MWE) of green tea polyphenols. MWE of green tea polyphenols has been investigated as an alternative to water extraction under conventional heating (CWE). The experimental conditions were selected after consideration of both temperature and extraction time. The efficiency and selectivity of the process were determined in terms of extraction time, total phenolic content, chemical composition (HPLC-MS analysis) and antioxidant activity of the extracts. By MWE (80 degrees C, 30 min), the flavanol content of the extract reached 97.46 (+/- 0.08) mg of catechin equivalent/g of green tea extract, vs. only 83.06 (+/- 0.08) by CWE (80 degrees C, 45 min). In particular, the concentration of the most bioactive flavanol EGCG was 77.14 (+/- 0.26) mg of catechin equivalent/g of green tea extract obtained by MWE, vs 64.18 (+/- 0.26) mg/g by CWE. MWE appears more efficient than CWE at both 80 and 100 degrees C, particularly for the extraction of flavanols and hydroxycinnamic acids. Although MWE at 100 degrees C typically affords higher yields in total phenols, MWE at 80 degrees C appears more convenient for the extraction of the green tea-specific and chemically sensitive flavanols.

A continuous approach for the determination of Cr(VI) in sediment and soil based on the coupling of microwave-assisted water extraction, preconcentration, derivatization and photometric detection

A dynamic system for the continuous leaching of Cr(VI) from sediment and soil based on both microwave assistance and iterative change of the flow direction of the extractant through the sample cell has been developed. The microwave-assisted extractor has been coupled to a photometric detector through a flow injection interface in order to develop a fully automated method. The Cr(VI) extracted was monitored after derivatization with 1,5-diphenylcarbazide. Two approaches are proposed which differ in the inclusion of a preconcentration minicolumn packed with a strong anion exchange resin. A 0.04 M ammonium buffer solution was used as extractant and 0.2 g of sample—river sediment spiked with 50 and 5 μg g −1 for the method without preconcentration (method A) and with preconcentration (method B)—was subjected to 8–14 min of 300 W microwave-assisted extraction. The within-laboratory reproducibility and repeatability were 2.6 and 1.9 for method A, and 4.0 and 2.6 for method B. The proposed methods have been compared with the reference EPA method 3060/7196.

A continuous approach for the determination of Cr(VI) in sediment and soil based on the coupling of microwave-assisted water extraction, preconcentration, derivatization and photometric detection

A continuous approach for the determination of Cr(VI) in sediment and soil based on the coupling of microwave-assisted water extraction, preconcentration, derivatization and photometric detection

Determination of metribuzin and major conversion products in soils by microwave-assisted water extraction followed by liquid chromatographic analysis of extracts

A multiresidue method developed for the analysis of metribuzin and its major conversion products, deaminometribuzin (DA), diketometribuzin (DK) and deaminodiketometribuzin (DADK), in soils is presented. The method is based on microwave-assisted water extraction (MAWE) of soils using 10 m M phosphate buffer, pH 7 as extractant and analysis of aqueous extracts by HPLC–diode array detection. MAWE operational parameters were optimized with respect to extraction efficiency of the target compounds from soils with 1.5 and 3.5% organic matter content. Recoveries of all solutes above 80% were obtained from soils with 1.5% organic matter content; respective LOD and LOQ levels were determined at 5 and 10 μg/kg. In soils with organic matter content 3.5%, recoveries of all solutes were lower (<70%) and the respective LOD and LOQ values were determined at 10 and 50 μg/kg. However, recoveries of fresh and aged residues, the latter weathered under cold storage conditions, were not statistically different for both types of soils.

Microwave-assisted water extraction of acid herbicides from soils coupled to continuous filtration, pre-concentration, chromatographic separation and UV detection

A microwave-assisted extraction procedure using water as extractant has been performed for the extraction of acid herbicides (namely, bentazone, 2,4-D, trichlopyr, 2,4,5-T and 2,4,5-Tp) from different types of soil. Two experimental designs were used for the optimization of the leaching step. The selection of water as extractant provided a clean approach by avoiding the use of organic solvents. The use of water also enhanced the extraction efficiency due to the high interaction of the microwave irradiation with polar solvents. The time required for total removal of the target compounds was 35 min. The recoveries yield were from 87.64 to 106.14% with a repeatability (expressed as relative standard deviation) ranging between 1.34 and 9.24%. A within-laboratory reproducibility, also expressed as relative standard deviation, varied from 3.97 to 10.41%. A flow-injection manifold allowed automation of the whole process by hyphenating the steps subsequent to extraction (namely, filtration, preconcentration, chromatographic separation and UV detection) for the determination of the analytes.