Recent extraction techniques for natural products: microwave-assisted extraction and pressurised solvent extraction

In the last 10 years there has been an increased interest in using techniques involving microwave-assisted extraction and pressurised solvent extraction in analytical laboratories. This review gives a brief overview of both methods, and reports on their application to the extraction of natural products. The influence of parameters such as the nature of the solvent and volume, temperature, time and particle size of the matrix is discussed. Through numerous examples, it is demonstrated that both techniques allow reduced solvent consumption and shorter extraction times, while the extraction yields of the analytes are equivalent to or even higher than those obtained with conventional methods.     

Butanol recovery from fermentations by liquid-liquid extraction and membrane solvent extraction

Extraction can successfully be used for in-situ alcohol recovery in butanol fermentations to increase the substrate conversion. An advantage of extraction over other recovery methods may be the high capacity of the solvent and the high selectivity of the alcohol/water separation. Extraction, however, is a comprehensive operation, and the design of an extraction apparatus can be complex. The aim of this study is to assess the practical applicability of liquid-liquid extraction and membrane solvent extraction in butanol fermentations. In this view various aspects of extraction processes were investigated.Thirty-six chemicals were tested for the distribution coefficient for butanol, the selectivity of alcohol/water separation and the toxicity towards Clostridia. Convenient extractants were found in the group of esters with high molar mass.Liquid-liquid extraction was carried out in a stirred fermenter and a spray column. The formation of emulsions and the fouling of the solvent in a fermentation broth causes problems with the operation of this type of equipment. With membrane solvent extraction, in which the solvent is separated from the broth by a membrane, a dispersion-free extraction is possible, leading to an easy operation of the equipment. In this case the mass transfer in the membrane becomes important.With membrane solvent extraction the development of a process is emphasized in which the extraction characteristics of the solvent are combined with the property of silicone rubber membranes to separate butanol from water. In the case of apolar solvents with a high molar mass, the characteristics of the membrane process are determined completely by the solvent. In the case of polar solvents (e.g. ethylene glycol), the permselectivity of the membrane can profitably be used. This concept leads to a novel type of extraction process in which alcohol is extracted with a water-soluble solvent via a hydrophobic semipermeable membrane. This extraction process has been investigated for the recovery of butanol and ethanol from water. A major drawback in all processes with membrane solvent extraction was the permeation of part of the solvent to the aqueous phase.The extraction processes were coupled to batch, fed batch and continuous butanol fermentations to affirm the applicability of the recovery techniques in the actual process. In the batch and fed batch fermentations a three-fold increase in the substrate consumption could be achieved, in the continuous fermentation about 30% increase.     

连续逆流提取机及其在绞股蓝皂苷提取工艺中的应用

简述了中草药连续逆流提取机的基本结构和工作原理.以水为溶媒、绞股蓝为原料,进行绞股蓝有效成分的提取试验.以绞股蓝水溶出物和总皂苷为目标物,考察提取温度、液料比和提取时间等因素对提取得率的影响,并通过L9(33)正交实验设计,对提取工艺进行优选.采用中草药连续逆流提取机提取绞股蓝有效成分的最佳工艺条件:提取溶剂温度80 ℃,料液比1:35(g/mL),提取时间50 min;所得提取物得率为33.95%,总皂苷得率为8.9%.     

Forward and backward extraction rates of amino acid in reversed micellar extraction

The mass transfer characterization in reversed micellar extraction of amino acid phenylalanine (Phe) is presented. The mass transfer rates in forward extraction of Phe from aqueous KCl solutions (pH 1.4 – 2.3) to AOT/isooctane reversed micellar solutions and in backward extraction from the reversed micellar organic phase to KHCO₃/KOH buffer solutions (pH 9.0 – 11.0) were investigated using a stirred cell with a flat liquid–liquid interface. Both the forward and the backward extraction rates are controlled by the interfacial rate processes, i.e., the solubilization and the release processes. The solubilizing rate constants for the forward extraction of Phe increase with decreasing pH and initial Phe concentration and with increasing initial AOT concentration. On the other hand, the releasing rate constants for the backward extraction decrease with increasing initial AOT concentration and with decreasing ionic strength, but are little influenced by pH. The backward extraction rates are fairly slow compared to the forward extraction rates, and are accelerated by the addition of 2-methyl-2-propanol, similar to the extraction of protein lysozyme.     

Two phase aqueous extraction

Rheological properties have been measured for aqueous solutions of dextran, polyethylene glycol and bovine serum albumin. Mixtures of these materials have also been studied. A rotating concentric cylinder viscometer was used to study the rheological properties of these materials over the temperature range 10 to 40°C. Over the range of concentrations, molecular weights, temperature and shear rates covered in this work, all aqueous solutions exhibited Newtonian behaviour. Correlations have been reported for viscosities of dextran, polyethylene glycol, and bovine serum albumin. The viscosity of mixtures of these materials is not linear with respect to concentration.     

Endovascular extraction techniques for pacemaker and ICD lead extraction: Part 1

In the last few years, comprehensive endovascular techniques have been developed to extract chronically implanted pacemaker and defibrillator leads. It is important that referring physician have knowledge of the advantages and limitations of the different techniques. In this paper we discuss the techniques and results of the currently used endovascular extraction techniques.     

Reactive extraction of penicillin G from mycel-containing broth in a countercurrent extraction decanter

Penicillin was recovered from mycel-containing fermentation broth by direct reactive extraction into a counter-current extraction decanter, Type CA 226-290 of the Westfalia Separator Co., at room temperature via steady state operation. Penicillin concentrations in the feed varied from 3 to 41 g L(-1), Amberlite LA-2 carrier concentrations from 7 to 20 g L(-1)and/or DITDA carrier concentrations from 7.2 to 84 g L(-1), the LA-2-to-penicillin mole concentration ratio from 4 to 6.4, and/or the DITDA-to-penicillin mole concentration ratio was maintained at 2. The throughputs of the fermentation broth (520 to 880 L h(-1)) of the solvent phase (200 to 860 L h(-1)) and the over all throughput (800 to 1750 L h(-1)) were high. Extraction degrees of 72 to 96% were achieved between pH 4.6 and 5.1. Without carriers in the same pH range, extraction degrees of only 17 to 19% were attained. By reducing the pH to 2.3 and in the absence of carriers, the degree of extraction was increased to 61%. However, during the extraction, 6.5% of the penicillin decomposed. At these high throughputs, the steady state was attained within 1 to 4 min. Through the mechanical stress, the length of the hyphae was reduced and the protein content of the broth was increased by 50 to 100%. However, this protein content had no appreciable influence on the phase separation.     

Cataract extraction with erisophake

Today the erisophake offers the most successful means for the intracapsular extraction of cataracts. The advantages of this method are that no counterpressure is required so that the incidence of vitreous loss is reduced; the vacuum cup provides a firmer grasp of the lens with less danger of rupture of the lens capsule; and the vacuum cup can be used for the delivery of practically all types of cataract in the adult, including intumescent and Morgagnian cataracts as well as lenses with exfoliating and friable capsules. While the forceps method of intracapsular extraction is generally successful in not more than 70 to 75 per cent of cases, the erisophake may offer success in 90 per cent of cases.     

Determination of tobramycin in soil by HPLC with ultrasonic-assisted extraction and solid-phase extraction

Pharmaceuticals residues in the environment have become a growing scientific interest worldwide. In the light of the possible harmful effects of tobramycin, a rapid and sensitive analytical method for determination of tobramycin in soil was developed. The extraction and purification methods, derivatization conditions, and chromatographic conditions in the determination of tobramycin in soil have been fully investigated. Extraction was carried out by a combination of vortex mixer and ultrasonic oscillation using acetone/water as the extraction agent. The extract was concentrated to 1 mL and passed through the C(18) SPE cartridge rinsed with water (3 mL), methanol (3 mL). The derivatization procedure was followed by the reaction of tobramycin with 4-Chloro-3,5-dinitrobenzotrifluoride at 60°C for 10 min in pH 9.0 H(3)BO(3)-Na(2)B(4)O(7) medium. The labeled tobramycin was determined by high performance liquid chromatography at 245 nm. Separation was accomplished within 15 min in gradient elution mode with trifluoroacetic acid in mobile phase as ion-pair reagent. The correlation coefficient for the method was 0.9999 in concentrations ranging from 0.10 to 100.0 μg/g. The limit of detection was 0.02 μg/g for tobramycin in soil at a signal-to-noise ratio of 3. The calculated recoveries of the proposed method were from 78.0 to 91.0% and RSDs were 3.38-9.79% in the application to the quantitative determination of tobramycin in all types of soil. The method will help to establish adequate monitoring of tobramycin residue in soil and make the contribution to environmental behavior evaluation.     

Coextraction during reactive extraction of phenylalanine using Aliquat 336: modeling extraction equilibrium

Reactive liquid-liquid extraction can be used to recover hydrophilic fermentation products that would not otherwise partition into nonpolar solvents through an ion-exchange reaction at the two-phase interface. However, the ion-exchange reagent may not be specific to the solute of interest and other compounds present may also be extracted. In this study, the effect on solute extraction of other compounds present in the extraction medium was investigated for phenylalanine extraction using Aliquat 336. The extent of extraction at equilibrium was modeled using the equilibrium constants for the reactions present in the process. The interaction of different species within a multicomponent medium was examined using the model and experimental results. It was found that the extent of extraction and coextraction is controlled by the thermodynamics of each extraction reaction and, due to the formation of a common product, the interaction between each of the reactions. The main competition to reactive extraction will come from hydrophobic anionic compounds that will be present in fermentation broth.     

Effect of salts on the extraction characteristics of succinic acid by predispersed solvent extraction

Predispersed solvent extraction (PDSE) of succinic acid with Tri-n-octylamine (TOA) dissolved in 1-octanol from aqueous solutions of 50 g/L succinic acid was examined. It was found that the equilibrium data in PDSE was equal to that in conventional solvent extraction in spite of the lack of mechanical mixing in PDSE. The influence of salts on succinic acid extraction and the stability of colloidal liquid aphrons (CLAs) were also investigated. Results indicated that in the presence of sodium chloride, less succinic acid was extracted by CLAs and the stability of CLAs decreased. However, the stability of CLAs was sufficient to make PDSE practically applicable to real fermentation broth, considering the concentration range of salts in the fermentation process for succinic acid.     

Soil saccharide extraction and detection

Extraction of soil saccharides involves the use of reagents effective in breaking hydrogen and covalent bonds between soil constituents and the saccharides. Of the many extractants proposed for saccharide determination, water is commonly used for extraction of water-soluble mono- and polysaccharides in soil. Analysis of these water extracts by colorimetric assays (anthrone-sulfuric acid and phenol-sulfuric acid methods) often show color development indicating that saccharides are present. However, high performance liquid chromatography (HPLC) and gas chromatography analyses have indicated that these colorimetric assays are prone to errors due to interferences from inorganic soil constituents such as Cl⁻, NO₃ ⁻ and Fe⁺³. When water extracts (25° or 80°C) are put through deionization resins to remove interferences little to no saccharides are present when assayed by the phenol-sulfuric acid analysis. The inability of water to extract saccharides from soil or microbial polymers was confirmed by HPLC analysis. The phenol-sulfuric acid assay was found to be acceptable for saccharide analysis of soil extracts only after being subjected to resin deionization for interference removal. The anthrone-sulfuric acid method is not considered acceptable for determining saccharides in soil.     

DNA extraction from crayfish exoskeleton

Crayfish exoskeleton (CE) samples are generally less invasive and easy to be collected. However, it is difficult to extract DNA from them. This study was intended to investigate CE as a DNA source and design an easy and efficient DNA extraction protocol for polymerase chain reactions. Specific primer pair (PPO-F, PPO-R) was used to amplify extracted DNA from CE, and compared to crayfish tail muscle DNA sample. Moreover, seven microsatellites markers were used to amplify the CE DNA samples set. Since the extracted DNA from CE is suitable for gene amplification, the results present usefulness of CE as an easy and convenient DNA source for PCR-based population genetic research.     

Contour extraction of Drosophila embryos

Contour extraction of Drosophila (fruit fly) embryos is an important step to build a computational system for matching expression pattern of embryonic images to assist the discovery of the nature of genes. Automatic contour extraction of embryos is challenging due to severe image variations, including 1) the size, orientation, shape, and appearance of an embryo of interest; 2) the neighboring context of an embryo of interest (such as nontouching and touching neighboring embryos); and 3) illumination circumstance. In this paper, we propose an automatic framework for contour extraction of the embryo of interest in an embryonic image. The proposed framework contains three components. Its first component applies a mixture model of quadratic curves, with statistical features, to initialize the contour of the embryo of interest. An efficient method based on imbalanced image points is proposed to compute model parameters. The second component applies active contour model to refine embryo contours. The third component applies eigen-shape modeling to smooth jaggy contours caused by blurred embryo boundaries. We test the proposed framework on a data set of 8,000 embryonic images, and achieve promising accuracy (88 percent), that is, substantially higher than the-state-of-the-art results.     

An improved phycobilin extraction method

One unique feature in cyanoprokaryotes, rhodophytes, and cryptophytes is the presence of phycobilin pigments-these water soluble pigments can absorb red, orange, yellow, and green light enhancing the spectral range available for cellular conversion to chemical energy. The presence of phycobilin pigment complexes can be detected using fluorescence, or absorbance measures. Efficient detection of these compounds is essential for use in calibrating absorbance in remote sensing or in physiological studies. The standard procedure for phycobilin analysis involves sonication, extraction in buffer potentially coupled with additional digestion steps using enzymes, repeated freeze and thawing cycles, followed by filtration, and spectrophotometric analyses. An alternative method, using asolectin-CHAPS ((3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid – AC)) solution for extraction, and three cycles of freeze/thawing/sonication, was compared to the phosphate buffer (PB) standard procedure. Cultures of both coccoid and filamentous cyanoprokaryota had improved extraction efficiency (38–80%) using AC. After two complete extractions, no pigment was detectable in AC and near baseline fluorescence was observed in the cell pellet, whereas the PB extraction method removed <90% of the phycobilins after two extractions. Phycocyanin concentration measured by AC extraction was better correlated to lipophilic pigment concentration than using phosphate buffer extraction. AC buffered to pH 6.7 was more effective than AC 3.75. One potential source of experimental error was determined to be the use of a baseline correction for the extraction buffer, not the sample.     

RNA extraction from plant tissues

Several protocols and commercial kits are used for the extraction of nucleic acids from different plant tissues. Although there are several procedures available to remove sugars, which hinder the extraction of clean genomic DNA, there are few to assist with extraction of RNA. Those presently used include precipitations with ethylene glycol monobutyl ether or lithium chloride (LiCl), or centrifugation in cesium chloride (CsCl) gradients, but these generally either do not allow high recovery of RNA, are time consuming, rely on hazardous chemicals or need special equipment. Here we present the use of the simple cation, Ca²⁺, which has been tested and shown to be very efficient for the precipitation of high molecular weight pectic sugars during RNA extraction. Results are presented for different plant tissues, especially tissues of peach and apple fruits at varying ripening stages.     

Optimization of cyclotide extraction parameters

Cyclotides are gene-encoded plant mini-proteins that contain a unique circular and cystine knotted amide backbone. Because of that ultra stable scaffold and the ability to harness a wide variety of sequences and biological activities within the scaffold, cyclotides find interesting potential applications for drug discovery and in agriculture. However, some fundamental knowledge is still missing to exploit these plant compounds, including finding the optimal process of their extraction from plant material. In the current work, the extraction parameters solvent type, time of extraction, number of re-macerations and the plant material to solvent ratio have been compared using the sweet violet (Viola odorata L.) as a model plant. That species is a well-characterized and rich source of cyclotides that contains prototypic cyclotides with different chemical and physical properties. We found that hydroalcoholic solutions of medium polarity give good yield of the cyclotide cocktail. In conclusion, single maceration with 50% MeOH for 6 h at a plant material to solvent ratio of 0.5:10 (g/mL) represents an optimum extraction method.