Extraction of nutraceuticals from milk thistle

Milk thistle contains compounds that display hepatoxic protection properties. We examined the batch extraction of silymarin compounds from milk thistle seed meal in 50, 70, 85, and 100°C water as a function of time. After 210 min of extraction at 100°C, the yield of taxifolin was 1.2 mg/g of seed, a 6.2-fold increase over the results obtained in a Soxhlet extraction with ethanol on pretreated (defatted) seeds. Similarly, the yield of silychristin was 5.0 mg/g of seed, a 3.8-fold increase. The yields of silybinin A and silybinin B were 1.8 and 3.3 mg/g of seed, respectively, or roughly 30% of the Soxhlet yield. The ratios of the extracted compounds, and particularly the ratios at long extraction times, showed that the more polar compounds (taxifolin and silychristin) were preferentially extracted at 85°C, while the less polar silybinin was favored at 100°C.     

Pressurized hot water extraction (PHWE)

Pressurized hot water extraction (PHWE) has become a popular green extraction method for different classes of compounds present in numerous kinds of matrices such as environmental, food and botanical samples. PHWE is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and soils/sediments for environmental monitoring purposes. The main parameters which influence its extraction efficiency are namely the temperature, extraction time, flow rates and addition of modifiers/additives. Among these different parameters studied, temperature is described as the most important one. It is reported that the extraction of certain compounds is rather dependent on pressurized water with different applied temperature. Thus, the stability and reduced solubilities of certain compounds at elevated temperatures are highlighted in this review. With some modifications, a scaled-up PHWE could extract a higher amount of desirable compounds from solid and powdered samples such as plant and food materials. The PHWE extracts from plants are rich in chemical compounds or metabolites which can be a potential lead for drug discovery or development of disease-resistant food crops.     

Comparison of different trapping methods for pressurised hot water extraction

Four trapping methods for pressurised hot water extraction were compared in terms of recovery and selectivity. Also, robustness, repeatability and solvent consumption of the trapping systems were investigated. The trapping methods were collection into solvent following liquid-liquid extraction, solid-phase trapping into Tenax TA (SPE), flat sheet microporous membrane liquid-liquid extraction and hollow fibre microporous membrane liquid-liquid extraction. Polycyclic aromatic hydrocarbons were extracted with these systems from four soil and sediment matrices and the extracts were analysed by GC-MS and size-exclusion chromatography. Clear differences were observed in the selectivity and extraction efficiencies of the trapping systems.     

Pressurized hot water extraction of berberine, baicalein and glycyrrhizin in medicinal plants

Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC.     

Fast extraction of amphenicols residues from raw milk using novel fabric phase sorptive extraction followed by high-performance liquid chromatography-diode array detection

A simple, sensitive, reliable, and fast analytical method was developed for the simultaneous determination of amphenicols residues in raw milk by combining fabric phase sorptive extraction (FPSE) and high-performance liquid chromatography-diode array detection. FPSE, a new generation green sample preparation technique, efficiently incorporates the advanced and tunable material properties of sol–gel derived microextraction sorbents with the rich surface chemistry of a cellulose fabric substrate, resulting in a flexible, highly sensitive, and fast microextraction device capable of extracting target analytes directly from complicated sample matrices. Due to the strong chemical bonding between the sol–gel sorbent and substrate, the microextraction device demonstrates a very high chemical and solvent stability. Therefore, any organic solvent/solvent mixture can be used as the eluent/back-extraction solvent.     

Isolation of flavonoids from aspen knotwood by pressurized hot water extraction and comparison with other extraction techniques

Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized for the extraction of naringenin and other major flavonoids (dihydrokaempferol, naringin) from knotwood of aspen. Extracts were analysed by GC-FID, GC-MS, HPLC-UV and HPLC-MS. The results were compared with those obtained by Soxhlet, ultrasonic extraction and reflux in methanol. Flavonoids were most efficiently extracted with PHWE at 150 °C and 220 bar with 35 min extraction time. Soxhlet with methanol gave slightly higher recoveries, but an extraction time of 48 h was required. Naringenin concentration was highest in knotwood (1.15% dry weight) and much lower in the sapwood. PHWE proved to be cheap, fast and effective for the isolation of biofunctional flavonoids from aspen knotwood, producing higher recoveries than 24 h Soxhlet extraction, sonication or 24 h reflux.     

Determination of senkirkine and senecionine in Tussilago farfara using microwave-assisted extraction and pressurized hot water extraction with liquid chromatography tandem mass spectrometry

Tussilago farfara (Kuan Donghua) is an important Chinese herbal medicine which has been shown to contain many bioactive compounds and widely used to relieve cough and resolve phlegm. However, besides therapeutic bioactive compounds, this herb has been found to contain toxic pyrrolizidine alkaloids (PAs), mainly senkirkine and traces of senecionine. In this report, conditions for microwave-assisted extraction (MAE) and pressurized hot water extraction (PHWE) were optimized for the extraction of the PAs. The results were compared against heating under reflux. It was found that the binary mixture of MeOH:H₂O (1:1) acidified using HCl to pH 2-3 was the optimal solvent for the extraction of the PAs in the plant materials. Liquid chromatography (LC) with ultra-violet (UV) detection and electrospray ionization mass spectrometry (ESI-MS) in the positive mode was used for the determination and quantitation of senkirkine and senecionine in the botanical extract. The proposed extraction methods with LC/MS allow for the rapid detection of the major and the minor alkaloids in T. farfara in the presence of co-eluting peaks. With LC/MS, the quantitative analysis of PAs in the extract was done using internal standard calibration and the precision was found to vary from 0.6% to 5.4% on different days. The limits of detection (LODs) and limits of quantitation (LOQs) for MAE and PHWE were found to vary from 0.26 μg/g to 1.04 μg/g and 1.32 μg/g to 5.29 μg/g, respectively. The method precision of MAE and PHWE were found to vary from 3.7% to 10.4% on different days. The results showed that major and minor alkaloids extracted using MAE and PHWE were comparable to that by heating under reflux. Our data also showed that significant ion suppression was not observed in the analysis of senkirkine and senecionine in the botanical extracts with co-eluting peaks.     

Isolation of tetracyclines in milk using a solid-phase extracting column and water eluent

An isolating method using a solid-phase extraction (SPE) ISOLUTE® C8 endcapped syringe-column for routine monitoring of residual tetracyclines (TCs) (oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), and doxycycline (DC)) in cow's milk is presented. In the simplest and most environmentally harmless method, milk samples could be applied directly to the SPE column, following which all TCs were eluted with water. No organic solvents were used at all. The purified sample was injected into a high-performance liquid chromatography (HPLC) with a photo-diode array detector (PDAD). For the HPLC determination/identification, a LiChrospher® 100 RP-8 endcapped column and a mobile phase of acetonitrile −7% (v v⁻¹) acetic acid solution (in water) (35:65, v v⁻¹) with a PDAD was used. The total time required for the analysis of one sample was <40 min. Average recoveries (spiked 0.1-1.0 μg ml⁻¹ each drug) and their standard deviations were >80 and <5%, respectively.     

Effect of extraction vessel geometry and flow homogeneity on recoveries of polycyclic aromatic hydrocarbons in pressurised hot water extraction

Extraction vessels of different length, internal diameter and volume were tested to evaluate the effect of vessel geometry on the recovery of polycyclic aromatic hydrocarbons (PAHs) from certified sediment by pressurised hot water extraction (PHWE). Pressurised hot water extractions were performed at 300 °C with both liquid water (pressure 250 kg cm^–2) and steam (pressure 50 kg cm^–2). In addition, the effects on the recoveries of sediment packing and water flow direction were examined in two vessels. The geometry of the vessel, the packing of the sediment and the flow direction of the water had only minor effect on the recoveries.     

Optimizing conditions for the extraction of catechins from green tea using hot water

Six different factors involved in the extraction of catechins from green tea using water were examined for their impact on the yield of catechins and on the efficiency of water use. The best temperature and time combination for catechin extraction was at 80°C for 30 min. The yield of catechins was also optimal with a tea particle size of 1 mm, a brewing solution pH <6 and a tea‐to‐water ratio at 50:1 (mL/g). In terms of efficient use of water in a single extraction, a water‐to‐tea ratio of 20:1 (mL/g) gave the best results; 2.5 times less water was used per gram of green tea. At the water‐to‐tea ratio of 20:1 mL/g, the highest yield of catechins per gram of green tea was achieved by extracting the same sample of green tea twice. However, for the most efficient use of water, the best extraction was found to be once at a water‐to‐tea ratio of 12:1 (mL/g) and once at a water‐to‐tea ratio of 8:1 (mL/g). Therefore, all six of the factors investigated had an impact on the yield of catechins extracted from green tea using water and two had an impact on the efficiency of water use.     

Automated on-fiber derivatization with headspace SPME-GC-MS-MS for the determination of primary amines in sewage sludge using pressurized hot water extraction

An automated, environmentally friendly, simple, selective, and sensitive method was developed for the determination of ten primary aliphatic amines in sewage sludge at μg/kg dry weight (d.w.). The procedure involves a pressurized hot water extraction (PHWE) of the analytes from the solid matrix, followed by a fully automated on‐fiber derivatization with 2,3,4,5‐pentafluorobenzaldehyde (PFBAY) and headspace solid‐phase microextraction (HS‐SPME) and subsequent gas chromatography ion‐trap tandem mass spectrometry (GC‐IT‐MS‐MS) analysis. The limits of detection (LODs) of the method were between 0.5 and 45 μg/kg (d.w.) for all compounds except for ethyl‐, isopropyl‐, and amylamine, whose LODs were 70, 109, and 116 μg/kg (d.w.), respectively. The limits of quantification (LOQs) were between 10 and 350 μg/kg (d.w.). Repeatability and intermediate precision, expressed as RSD(%) (n=3), were lower than 18 and 21%, respectively. The method developed enabled to determine primary aliphatic amines in sludge from various urban and industrial sewage treatment plants as well as from a potable treatment plant. Most of the primary aliphatic amines were found in the sewage sludge samples analyzed corresponding to the maximum concentrations to the samples from the urban plant: for instance, isobutylamine and methylamine were found at 7728 and 12 536 μg/kg (d.w.), respectively. Amylamine was detected only in few samples but always at concentrations lower than its LOQ.     

Determination of quinolones in milk samples using a combination of magnetic solid-phase extraction and capillary electrophoresis

A magnetic solid-phase extraction (MSPE) method combined with capillary electrophoresis for the simultaneous determination of seven quinolones (QNs) (danofloxacin, ciprofloxacin, marbofloxacin, enrofloxacin, difloxacin, oxolinic acid, and flumequine), using (S)-(+)-6-methoxy-α-methyl-2-naphthaleneacetic acid as internal standard, in milk samples was developed. The variables involved in the preconcentration magnetic procedure were: the composition of the magnetic support composition, the sample pH, and the weight of magnetic adsorbent used. The variables were optimized using a simplex-lattice design. Different magnetite covered with octyl-phenyl silica adsorbents were synthesized by varying the molar ratio of phenyltrimethylsilane and octyltrimethoxysilane; the solids were evaluated for QN preconcentration. Under optimal conditions, a linear range was obtained from 27 to 1000 μg L(-1) with limits of detection ranging from 9 to 12 μg L(-1) for the seven QNs. The absolute recoveries of the seven QNs at three different spiked levels (40, 150, and 400 μg L(-1) ) ranged from 74% to 98% with a relative standard deviation less than 10% in all cases. The proposed method was applied to analyze 20 whole milk samples of different brands. All samples were positive for the presence of QN residues; in some cases, extract dilution was required. The concentrations found are in the range from 31.1 to 5047.3 μg L(-1) . Marbofloxacin was the most frequently found. The method proposed offers advantages in terms of simplicity, sensitivity, efficiency, cost, and analysis time making it an alternative for the analysis of QNs in whole milk samples.     

Evaluation of surfactant‐assisted pressurized hot water extraction for marker compounds in Radix Codonopsis pilosula using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry

In the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants.     

Evaluation of double solid-phase extraction system for determining triazine herbicides in milk

Summary High-performance liquid chromatography with UV detection was used to determine eight triazine herbicides in milk. Solid-phase extraction was performed using a double trap; first, a nonspecific adsorbent (Carbograph), and then a cation exchanger (SCX). Eluate from the SCX was evaporated to dryness under reduced pressure and redissolved in mobile phase. An aliquot was injected into the chromatograph, which was operated isocratically in the reverse-phase mode with UV detection at 225 nm. Analytical recoveries for the eight triazines ranged from 73.0 % to 92.4 %. The limit of sensitivity of this method was about 0.09 ng mL⁻¹ of milk. The method was validated and evaluated by comparison with a method reported in literature.     

Evaluation of double solid-phase extraction system for determining triazine herbicides in milk

Summary High-performance liquid chromatography with UV detection was used to determine eight triazine herbicides in milk. Solid-phase extraction was performed using a double trap; first, a nonspecific adsorbent (Carbograph), and then a cation exchanger (SCX).Eluate from the SCX was evaporated to dryness under reduced pressure and redissolved in mobile phase. An aliquot was injected into the chromatography, which was operated isocratically in the reverse-phase mode with UV detection at 225 nm.Analytical recoveries for the eight triazines ranged from 73.0% to 92.4%. The limit of sensitivity of this method was about 0.09 ng mL^–1 of milk. The method was validated and evaluated by comparison with a method reported in literature.     

Static-dynamic pressurized hot water extraction coupled to on-line filtration-solid-phase extraction-high-performance liquid chromatography-post-column derivatization-fluorescence detection for the analysis of N-methylcarbamates in foods

A combination of static-dynamic modes of pressurized hot water extraction has been used for the extraction of N-methylcarbamates (namely, oxamyl, dioxacarb, metholcarb, carbofuran and carbaryl) from different fruits and vegetables. The selection of water as leaching agent provides a clean approach which avoids the use of organic solvents. A flow injection manifold coupled to the extractor has allowed the automation of the subsequent steps (namely, filtration, preconcentration, individual chromatographic separation, post-column derivatization and fluorescence detection) involved in the analytical process. Good recoveries, ranging from 80 to 104%, and precision, expressed as relative standard deviation, between 3.0 and 8.4% have been achieved by the proposed method.     

Ethanol production from olive oil extraction residue pretreated with hot water

The olive pulp fraction contained in the residue generated in olive oil extraction by a two-step centrifugation process can be upgraded by using the cellulose fraction to produce ethanol and recovering high value phenols (tyrosol and hydroxytyrosol). Olive pulp was pretreated in a laboratory scale stirred autoclave at different temperatures (150–250°C). Pretreatment was evaluated regarding cellulose recovery, enzymatic hydrolysis effectiveness ethanol production by a simultaneous saccharification and fermentation process (SSF), and phenols recovery in the filtrate. The pretreatment of olive pulp using water at temperatures between 200°C and 250°C enhanced enzymatic hydrolysis. Maximum ethanol production (11.9 g/L) was obtained after pretreating pulp at 210°C in a SSF fed-batch procedure. Maximum hydroxytyrosol recovery was obtained in the liquid fraction when pretreated at 230°C.     

Determination of parabens in house dust by pressurised hot water extraction followed by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

This study describes the development of a new method for determining p-hydroxybenzoic esters (parabens) in house dust. This optimised method was based on the pressurised hot water extraction (PHWE) of house dust, followed by the acetylation of the extracted parabens, stir bar sorptive extraction (SBSE) with a polydimethylsiloxane stir bar, and finally analysis using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The combination of SBSE and PHWE allows the analytes to be preconcentrated and extracted from the aqueous extract in a single step with minimal manipulation of the sample. Furthermore the in situ acetylation of parabens prior to SBSE improved their extraction efficiency and their GC-MS signal. The method showed recoveries of between 40 and 80%, good linearity, repeatability and reproducibility (<10% RSD, at 100 ng g(-1), n=5), low limits of detection (from 1.0 ng g(-1) for propyl paraben to 2.1 ng g(-1) for methyl paraben) and quantification (from 3.3 ng g(-1) for propyl paraben to 8.5 ng g(-1) for methyl paraben). The proposed method was applied to the analysis of house dust samples. All the target parabens were found in the samples. Methyl and propyl parabens were the most abundant, with concentrations up to 2440 ng g(-1) and 910 ng g(-1), respectively. The high levels of parabens found in the samples confirm the importance of determining organic contaminants in indoor environments.     

Determination of benzoic acid in milk by solid-phase extraction and ion chromatography with conductivity detection

A simple, fast, precise and eco-friendly method, based on ion chromatography (IC) with a suppressed conductivity detector, was proposed for the determination of benzoic acid (BA) inmilk in this paper. The chromatographic separation was accomplished by using an anion exchange column eluted with 3.2 μmol/L aqueous Na2CO3 and 1.0 mmol/L aqueous NaHCO3 at a flow-rate of 0.7 mL/min. Themethod validation experiment provided excellent results with respect to linearity (correlation coefficient up to 0.9997), limit of detection (0.1 μg/L), recovery values (ranging from 88.0% to 93.0%) and relative standard deviation (RSD) (below 2.2%, n = 7).     

Preconcentration of milk proteins using octadecylated monolithic silica microchip

Sample preparation is a bottleneck in systems for chemical analysis and it is a required step in order to remove interference and preconcentrate the target analytes. Much research in recent years has focused on porous monolithic materials since they are highly permeable to liquid flow and show high mass transfer compared with common packed beds. This study has focused on the use of a glass microchip containing an inorganic silica-based monolithic material modified with octadecyl groups for preconcentration of milk proteins from skimmed cows’ milk that vary in molecular weight, hydrophobicity, and abundance. Comparison between the fabricated device and a commercial cartridge for the preconcentration of proteins in skimmed cows’ milk showed the ability of the device to successfully enrich protein mixtures from the sample. The three replicate experiments showed that the RSD of the mass to charge ratio of milk proteins ranged from 0.01 to 0.46%. In addition, it was found that there were no significant differences between the observed and reported masses of the milk proteins and the relative percentage error of the molecular masses ranged between 0.03 and 0.90%. The fact that the small amounts of sample required and short sample preparation time suggest that this new microfluidic device may be a viable alternative to existing procedures for protein extraction from real samples.