Optimizing Microwave‐Assisted Extraction Conditions to Obtain Phenolic‐Rich Extract from Chromolaena odorata Leaves

Phenolic compounds are secondary metabolites that are mainly responsible for different pharmacological activities of plant extracts. In this study, microwave‐assisted extraction (MAE) variables were optimized for the extraction of phenolic compounds from Chromolaena odorata leaves by using a Box‐Behnken design of response surface methodology. The concentration of polyphenols and functional characteristics of the extracts were identified by using liquid chromatography quadrupolar time‐of‐flight mass spectrometry and FTIR analyses, respectively. The obtained results indicated the MAE conditions for the optimal recoveries of the total phenolic content and total flavonoid content from C. odorata leaves. The results reveal that the C. odorata leaf is enriched with phenolic compounds.     

Equilibrium and Kinetics of the Extraction of Propionic Acid Using Tri‐n‐Octylphosphineoxide

Organophosphorous compounds have been widely used in inorganic analysis for the extraction and separation of inorganic acids or metal species. Since these compounds can form hydrogen bonds to proton donors, they can also be used for the extraction of acidic organic compounds. Therefore, the reactive extraction of propionic acid using tri‐n‐octylphosphine oxide (TOPO) in hexane was studied. Equilibrium and kinetics experiments were performed. The extraction of propionic acid using n‐heptane, light liquid paraffin, heavy liquid paraffin and hexane was studied and hexane was found to be most suitable diluent. The equilibrium complexation constant for the propionic acid‐TOPO complex was determined to be 0.702 m³/kmol. The extraction was found to be first order in propionic acid and first order in TOPO with the overall rate constant as 46.91 (m³/kmol)²/s.     

Kinetic study of nordihydroguaiaretic acid recovery from Larrea tridentata by microwave‐assisted extraction

BACKGROUND: Nordihydroguaiaretic acid (NDGA) is a powerful antioxidant with biological activities of great interest in several health areas, including antiviral, cancer chemopreventive, and antitumorgenic. Little information is available on extraction methods of NDGA from Larrea tridentata. Hence, the aim of this study was to develop a rapid and effective microwave‐assisted extraction (MAE) method for NDGA recovery from Larrea tridentata leaves, and to compare the results obtained with those found using conventional heat‐reflux extraction (HRE). RESULTS: Extraction time for similar NDGA yields was significantly reduced from 18 to 1 min when MAE was used instead of HRE. Optimum conditions for NDGA extraction (3.79 ± 0.65%) consisted in using 50% methanol as extraction solvent in a solid/liquid ratio of 1/10 g mL^?1. Micrographs demonstrated that the improvement in NDGA extraction by MAE might be related to a greater extent of cell rupture of the plant material. Extracts obtained by MAE exhibited antiradical activity only slightly lower than those obtained by HRE. CONCLUSIONS: MAE proved to be a faster and more efficient method for NDGA extraction from Larrea tridentata leaves than HRE. The better results for NDGA extraction by MAE might be explained by the greater extent of cell rupture of plant material during the extraction process. Copyright © 2010 Society of Chemical Industry     

Determination of Anti-Tumor Constitute Mollugin from Traditional Chinese Medicine Rubia cordifolia: Comparative Study of Classical and Microwave Extraction Techniques

Abstract

Rubia cordifolia is a common traditional Chinese medicine (TCM) used for centuries for the treatment of cough, inflammation of the joints, uterine hemorrhage, and uteritis. Mollugin is a major active component present in R. cordifolia and recognized as a potential anti-tumor compound. In this work, a microwave-assisted extraction (MAE) method has been developed for extracting mollugin from R. cordifolia. Several variables that can potentially affect the extraction yield, namely extracting solvent, microwave power, extraction time, and solid-liquid ratio were optimized. The separation and quantitative determination of mollugin was carried out by HPLC with UV detection at 254 nm. Under appropriate MAE conditions, such as extraction time of 4 min, ethanol concentration of 70% (v/v), microwave power of 460 W, and solid-liquid ratio of 1:20 (g/mL), the extraction yield of mollugin from R. cordifolia with MAE was higher than conventional extraction methods such as Soxhlet extraction, heat reflux extraction, and ultrasonic-assisted extraction. Due to the considerable saving in time and its higher extraction yield, the proposed MAE procedure was obviously a more rapid and effective sample preparation technique.     

Optimization of Microwave‐Assisted Extraction of Flavonoid from Radix Astragali using Response Surface Methodology

Abstract

Response surface methodology (RSM) was applied to predict optimum conditions for microwave‐assisted extraction (MAE) of flavonoid from Radix Astragali. A central composite design was used to monitor the effect of temperature, extraction time, solvent‐to‐material ratio, and the ethanol concentration on yield of total flavanoid (TFA). Optimum extraction conditions were predicted as 108.2°C, 26.7 min, 23.1 ml/g solvent‐to‐material ratio and 86.2% ethanol. The maximum yield 1.234±0.031 mg/g was close to the yield of Soxhlet and higher than that of ultrasound assisted extraction and heat reflux extraction. MAE was an effective alternative to conventional extraction methods.     

Optimization of Microwave-Assisted Extraction of Astaxanthin from Haematococcus Pluvialis by Response Surface Methodology and Antioxidant Activities of the Extracts

Abstract

Microwave-assisted extraction (MAE) was applied for the extraction of astaxanthin from Haematococcus pluvialis and response surface methodology (RSM) was used to optimize extraction parameters to the content of astaxanthin. Four independent variables such as microwave power (W), extraction time (sec), solvent volume (mL), and the number of extraction were optimized in this paper. The optimal conditions were determined and tri-dimensional response surfaces were plotted from the mathematical models. The F-test and p-value indicated that microwave power, extraction time, the number of extraction, and their quadratic had a highly significant effect on the response value (p <0.01), then the solvent volume and the interaction effects of microwave power and the number of extraction also displayed significant effect (p <0.05). Considering the extraction efficiency, the optimized conditions of MAE were as follows: microwave power was 141 W, extraction time 83 sec, solvent volume 9.8 mL, the number of extraction four times. About 594 ± 3.02 µg astaxanthin was extracted from Haematococcus pluvialis the dried powders (100 mg) under the optimal conditions, and it close to the predicted contents (592 µg). The antioxidant activities of the extracts obtained under optimal conditions were analyzed, and the results showed that the extracts presented strong ability of inhibiting the peroxidantion of linoleic acid, exhibited strong radical-scavenging properties against the DPPH, as well as strong reducing power.     

Regio‐ and Stereospecific Prenylation of Flavonoids by Sophora flavescens Prenyltransferase

Prenylflavonoids are valuable natural products that are widely distributed in plants. They often possess divergent biological properties, including phytoestrogenic, anti‐bacterial, anti‐tumor, and anti‐diabetic activities. The reaction catalyzed by prenyltransferases represents a Friedel–Crafts alkylation of the flavonoid skeleton in the biosynthesis of natural prenylflavonoids and often contributes to the structural diversity and biological activity of these compounds. However, only a few plant flavonoid prenyltransferases have been identified thus far, and these prenyltransferases exhibit strict substrate specificity and low catalytic efficiency. In this article, a flavonoid prenyltransferase from Sophora flavescens, SfFPT, has been identified that displays high catalytic efficiency with high regiospecificity acting on C‐8 of structurally different types of flavonoid (i.e., flavanone, flavone, flavanonol, and dihydrochalcone, etc.). Furthermore, SfPFT exhibits strict stereospecificity for levorotatory flavanones to produce (2S)‐prenylflavanones. This study is the first to demonstrate the substrate promiscuity and stereospecificity of a plant flavonoid prenyltransferase in vitro. Given its substrate promiscuity and high catalytic efficiency, SfFPT can be used as an environmentally friendly and efficient biological catalyst for the regio‐ and stereospecific prenylation of flavonoids to produce bioactive compounds for potential therapeutic applications.     

微波辅助萃取技术在中药现代化中的应用

微波辅助萃取技术是近年来发展迅速的中药有效成分提取技术,与传统的中药活性成分提取技术相比,具有简便、快速高效、选择性强、能耗少和环境污染小等优点,因而越来越得到相关领域研究人员的关注。该文综述了近年来微波辅助萃取技术的原理、特点、影响微波萃取的主要因素、萃取装置及其在中药现代化中的研究进展。引用文献61篇。     

Scale‐up of Mini‐Plant Extractors on Energy Dissipation‐Based Population Balances

The new scale‐up concept for extraction columns relies on three identities being kept idem, as is the total specific flow rate, energy dissipation, and mean droplet residence time in a compartment. The droplet population balance‐based model allows maintaining hydrodynamic similarity in different geometries, as is in a mini‐ or a pilot plant. This leads to similar breakage and coalescence probabilities giving comparable droplet size distributions, thus mass transfer area and extraction efficiency. A new breakage frequency term has been developed relying on the energy dissipation rate and is thus independent from geometric constraints. The traditional scale‐up rules are based either on a constant tip velocity (≈ N) or on a constant energy input (≈ N³), whereas here it follows a constant energy dissipation (≈ N²). A step‐by‐step approach to the new procedure proved by case samples is given. Data from literature pilot experiments could be verified by computer simulations, without using adaptable parameters. All parameters in the correlations where derived in a lab‐scale apparatus and the coalescence parameters were obtained in the mini‐plant experiments. Derivation between simulated and experimental pilot data for stage numbers was less than 14 %, operating parameters (rotational speed N, throughput) were underestimated by 4 % leading to a slightly smaller HETS (Height Equivalent of Transfer Stages) value as measured, affecting the column height with less than 1 %.     

Enzymatic and Mechanical Extraction of Virgin Coconut Oil

The effect of different processing methods namely enzymatic method using crude protease extract (CPE) from overripe pineapple, microwave‐assisted extraction (MAE) and ultrasound‐assisted extraction (UAE) methods on the recovery yield of virgin coconut oil (VCO) is evaluated. The physicochemical properties of VCOs namely color, iodine value (IV), refractive index, saponification value, moisture content, free fatty acid, p‐anisidine value, lipid peroxidation, fatty acid composition, triacylglycerol (TAG) composition, melting and crystallization profile are compared. The total phenolic compounds and scavenging activity of the extracted VCOs are also examined. Results reveal that enzymatic approach exhibits the highest VCO yield (77.7% ± 0.38) at 50 °C for 2 h, followed by MAE (58.6%±0.07), control without enzyme (24.1%±0.19) and UAE (24.1%±0.12). The physicochemical properties of the VCOs extracted are found to conform to APCC standards established except IV. The antioxidant activity of VCO extracted with CPE shows no significant difference with MAE and UAE methods (p > 0.05). Lauric acid appears to be the most abundant fatty acid detected in all VCO samples. Similar exotherms and endotherms are observed in both melting and crystallization profiles with two distinct peaks exhibited. The TAG compositions of the extracted VCOs are mainly LaLaLa, LaLaM, CLaLa, CCLa, and LaMM (C = Capric acid; La = Lauric acid; M = Myristic acid). Practical Applications: The results obtained from this study indicate that VCO extraction using CPE from overripe pineapple is feasible. The enzymatic extraction protocol presented here would be useful for VCO production at industrial scale with a promising oil yield.     

Optimum conditions of microwave-assisted extraction for phenolic compounds and antioxidant capacity of the brown alga Sargassum vestitum

This study aimed to optimise microwave-assisted extraction (MAE) conditions for total phenolic compounds (TPCs) and antioxidant activities of the alga Sargassum vestitum by using response surface methodology with Box–Behnken design. The results showed that solvent concentration had the greatest impact on TPC and antioxidant activities of the extracts, followed by radiation time and power. The optimal MAE conditions were ethanol concentration of 70%, radiation time of 75 s and power of 80%. The optimal MAE method showed much better extraction efficacy of phenolics and antioxidant capacities of the extract than conventional and ultrasonic methods.     

Arabinosylated phenolics obtained from SO2‐steam‐pretreated sugarcane bagasse

A pentose‐rich hydrolysate fraction obtained by extraction of steam‐pretreated sugarcane bagasse was analysed with regard to dissolved phenolics. The liquid obtained after steam pretreatment (2% SO₂ (w/w) at 190 °C for 5 min) was divided into two parts: one containing dissolved compounds originating from hemicellulose (with xylose as the dominating compound), and the other containing predominantly dissolved compounds originating from lignin. Using nuclear magnetic resonance, the main dissolved compounds originating from lignin were identified as the glycosylated aromatics, 5‐O‐(trans‐feruloyl)‐L‐Arabinofuranose and 5‐O‐(trans‐coumaroyl)‐L‐Arabinofuranose, together with p‐coumaric acid and small amounts of more common free phenolics such as p‐hydroxybenzaldehyde, p‐hydroxybenzoic acid and vanillin. The phenolic compounds were analysed and quantified using reversed‐phase high‐performance liquid chromatography. The findings show that SO₂ steam explosion opened up new degradation pathways during lignin degradation. Copyright © 2012 Society of Chemical Industry     

A novel process for extraction of tea oil from Camellia oleifera seed kernels by combination of microwave puffing and aqueous enzymatic oil extraction

The objective of this study was to extract the oil from Camellia oleifera seed kernels by aqueous enzymatic oil extraction (AEOE). We describe a novel process for extraction of tea oil preceded by tea saponin extraction from C. oleifera seed kernels. The extraction efficiency obtained with microwave‐assisted extraction (MAE) is very high, which the recovery yield is up to 83% in 30 s and the saponins in camellia seed kernels can be completely removed by the second MAE. Moreover, an important step in the process development has been the pretreatment by microwave puffing of camellia seed kernel residues followed by AEOE increased oil extraction yield from 53% to 95%, which will is comparable to hexane oil extraction yields from plant materials.     

Recovery of Anti-Cancer Damnacanthal from Roots of Morinda citrifolia by Microwave-Assisted Extraction

Abstract

This study investigated the effects of material particle size, irradiation time, extraction temperature, type of solvents, ethanol composition, and the ratio of liquid-to-sample on microwave-assisted extraction (MAE) of roots of Morinda citrifolia to obtain the most important anti-cancer compound, damnacanthal. The highest recovery of the compound was obtained after 5 min of MAE of small particle size material at 100 and 120°C. Longer extraction time caused the decrease in percent recovery due to the decomposition of the compound. Among the pure solvents tested, acetone and methanol gave the highest recovery. However, the use of ethanol-water solution (80% v/v) could considerably improve the yield of damnacanthal extracted. MAE was found to give the highest extraction efficiency when compared with other extraction methods such as extraction with electrical heating, soxhlet extraction, and ultrasound-assisted extraction (UAE).     

Influence of Solvent Polarity on the Mechanism and Efficiency of Formic Acid Reactive Extraction with Tri‐n‐Octylamine from Aqueous Solutions

The reactive extractions of formic acid with tri‐n‐octylamine (TOA) dissolved in three solvents with different dielectric constants (dichloromethane, butyl acetate, n‐heptane) without and with 1‐octanol as phase modifier were comparatively analyzed. The results indicated that the mechanism of the interfacial reaction between acid and extractant (Q) is controlled by the organic phase polarity. In the absence of 1‐octanol, the structures of the extracted complexes are (HA)₂Q₂ for dichloromethane and butyl acetate, and (HA)₂Q₄ for n‐heptane. These structures are modified by adding 1‐octanol and become (HA)₂Q for extraction in dichloromethane or butyl acetate, and (HA)₂Q₂ for extraction in n‐heptane. Although the presence of 1‐octanol improves the extraction efficiency, it leads to a reduction of the extraction constants for all considered solvents, an influence that is more significant for n‐heptane.     

Sub‐and Supercritical CO2‐Extraction of Hypericum perforatum L.

The extraction of Hypericum perforatum L. by liquid carbon dioxide (p = 80 bar, t = 15 °C) gave almost the same extract yield (1 %, w/w) as by supercritical (p = 100 bar, t = 40 °C) carbon dioxide, containing the same percentages of essential oil (about 6.4 %, w/w). The increase of the extract yield at higher pressure (250 to 350 bar) is due to the increase of extragent density, i.e., solubility. By increasing the grinding degree of the drug, a higher extract yield is obtained in the supercritical range under high pressure. GC‐MS analysis of the extract composition showed that the non‐terpene compounds have the highest contribution. The oil content in the drug, determined by steam distillation, was 0.058 %, w/w. The oil content in the extracts, calculated for the drug, was significantly higher (1.2 to 1.9 times).     

Microwave-assisted extraction as an advanced technique for optimization of saponin yield and antioxidant potential from Phyllanthus amarus

The objective of this study was to apply microwave-assisted extraction (MAE) as an advanced technique for optimization of saponin yield and antioxidant potential from Phyllanthus amarus. The findings indicated that the optimal MAE parameters consisted of 100% methanol, irradiation time 4 s/min, extraction time 50 min, and solvent to sample ratio 50 mL/g. Under these optimal parameters, saponin content (SC), saponin extraction efficiency (SEE), and total phenolic content (TPC) of P. amarus were 229.5 mg escin equivalents (EEs)/g dried sample, 82.8%, and 40.7 mg gallic acid equivalents (GAEs)/g dried sample, respectively. The antioxidant capacity of P. amarus in terms of 2,2ˊ-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging capacity (ARSC), 2,2-diphenyl-1-picryl-hydrazil radical scavenging capacity (DRSC), and ferric reducing antioxidant power (FRAP) were 487.3, 330.6, and 233.5 mg trolox equivalents (TEs)/g dried sample, respectively. These measured values were not significantly different from the predicted values by response surface methodology (227.9 mg EE/g dried sample, 82.1%, and 39.2 mg GAE/g dried sample for SC, SEE, and TPC and 484.8, 297.3, and 226.6 mg TE/g dried sample for ARSC, DRSC, and FRAP, respectively). Hence, the optimal MAE parameters are suggested for effective extraction of saponins from P. amarus for further investigations and applications.     

Bioprocess scale‐up: quest for the parameters to be used as criterion to move from microreactors to lab‐scale

Advances in high‐throughput process development and optimization involve the rational use of miniaturized stirred bioreactors, instrumented shaken flasks and microtiter plates. As expected, each one provides different levels of control and monitoring, requiring a compromise between data quantity and quality. Despite recent advances, traditional shaken flasks with nominal volumes below 250 mL and microtiter plates are still widely used to assemble wide arrays of biotransformation/bioconversion data, because of their simplicity and low cost. These tools are key assets for faster process development and optimization, provided data are representative. Nonetheless, the design, development and implementation of bioprocesses can present variations depending on intrinsic characteristics of the overall process. For each particular process, an adequate and comprehensive approach has to be established, which includes pinpointing key issues required to ensure proper scale‐up. Recently, focus has been given to engineering characterization of systems in terms of mass transfer and hydrodynamics (through gaining insight into parameters such as k_La and P/V at shaken and microreactor scale), due to the widespread use of small‐scale reactors in the early developmental stages of bioconversion/biotransfomation processes. Within this review, engineering parameters used as criteria for scaling‐up fermentation/bioconversion processes are discussed. Particular focus is on the feasibility of the application of such parameters to small‐scale devices and concomitant use for scale‐up. Illustrative case studies are presented. Copyright © 2010 Society of Chemical Industry     

Coloration properties and chemo‐rheological characterization of a dioxazine pigment‐based monodispersed masterbatch

A dioxazine‐based color pigment was added to a commercial polyamide 6 (PA6) through an extrusion process, in order to prepare monoconcentrated violet masterbatches through different production set‐up. A detailed characterization of the resulting materials was carried out in order to find the best processing parameters combination to optimize pigment dispersion and to reduce the clogging power. The preparation of masterbatches with repeated extrusions markedly reduced the filter pressure value and increased the Relative Color Strength, while filtration did not significantly influence pigment dispersion. Rheological measurements and end‐groups analysis were conducted on the same materials with the aim to evaluate their thermal degradation resistance, and the thermal stability of the compounds was retained even upon three extrusions. Therefore, it can be concluded that a proper optimization of the process parameters could lead to an important reduction of the production waste, increasing the quality of the final product. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41452.     

Supercritical Carbon Dioxide and Microwave-Assisted Extraction of Functional Lipophilic Compounds from Arthrospira platensis

Arthrospira platensis biomass was used in order to obtain functional lipophilic compounds through green extraction technologies such as supercritical carbon dioxide fluid extraction (SFE) and microwave-assisted extraction (MAE). The temperature (T) factor was evaluated for MAE, while for SFE, pressure (P), temperature (T), and co-solvent (ethanol) (CS) were evaluated. The maximum extraction yield of the obtained oleoresin was (4.07% ± 0.14%) and (4.27% ± 0.10%) for SFE and MAE, respectively. Extracts were characterized by gas chromatography mass spectrometry (GC-MS) and gas chromatography flame ionization detector (GC-FID). The maximum contents of functional lipophilic compounds in the SFE and MAE extracts were: for carotenoids 283 ± 0.10 μg/g and 629 ± 0.13 μg/g, respectively; for tocopherols 5.01 ± 0.05 μg/g and 2.46 ± 0.09 μg/g, respectively; and for fatty acids 34.76 ± 0.08 mg/g and 15.88 ± 0.06 mg/g, respectively. In conclusion, the SFE process at P 450 bar, T 60 °C and CS 53.33% of CO₂ produced the highest yield of tocopherols, carotenoids and fatty acids. The MAE process at 400 W and 50 °C gives the best extracts in terms of tocopherols and carotenoids. For yield and fatty acids, the MAE process at 400 W and 70 °C produced the highest values. Both SFE and MAE showed to be suitable green extraction technologies for obtaining functional lipophilic compounds from Arthrospira platensis.