Supercritical Antisolvent Precipitation Research Articles

Supercritical antisolvent precipitation as a green technology to fractionate an Origanum majorana extract: Relationship between fractions cellular antioxidant activity and phytochemical composition.

The aim of this work was to determine the optimal conditions to fractionate a marjoram extract using supercritical antisolvent precipitation (SAS) technology in order to improve its antioxidant activity. This activity was evaluated using a cellular antioxidant assay (CAA) and compared to a chemical method (ABTS). After extract fractionation, most of the phenolics were recovered in the precipitate, except for the less polar ones that were found in the separators, along with essential oil components, non-volatile terpenes and fatty acids. Precipitate fractions obtained at 40 °C and 20–25 MPa showed the best TEAC values (1.7 mmol Trolox/g extract). Nevertheless, no precipitate fraction exerted better CAA than the unfractionated extract. This activity was related to the presence of arbutin and rosmarinic acid in their composition. In contrast, separators showed a low TEAC value (0.3 mmol Trolox/g), but a higher cellular antioxidant activity, especially fractions obtained at 15–20 MPa and 40–50 °C. This enhanced antioxidant activity was mainly attributed to the presence of ursolic acid, sterubin, menthol, sabinene hydrate and terpineol, compounds with a less polar character that therefore could cross more easily the cell membrane and exert their antioxidant activity inside the cells. Thus, separator fractions obtained at 20 MPa and 40 °C increased a 30% the CAA value respect to UAE extract and could be used for designing nutraceuticals or functional foods with cellular antioxidant activity. Precipitate fractions, at these extraction conditions, also showed an increase in TEAC value (40%) and could be employed as natural antioxidants in food formulations.

Novel bioactive extract from yarrow obtained by the supercritical antisolvent-assisted technique inhibits lipid metabolism in colorectal cancer.

Background: Altered lipid metabolism in cancer is associated to dissemination and prognosis. Bioactive compounds naturally occurring in Achillea millefolium L. (yarrow) have been reported to exert antitumour activities. Food biotechnology may provide on-demand mixtures of bioactive compounds with complementary activities in cancer treatment. Methods: Supercritical-antisolvent-precipitation (SAS) has been applied to fractionate the bioactive compounds from an Ultrasound-Assisted-Extraction yarrow extract resulting in two extracts with distinct polarity, yarrow-precipitate-(PP) and yarrow-separator-(Sep). Total phenolic content and relevant essential oils have been characterized. Antioxidant, anti-inflammatory and antiproliferative activities have been compared. Moreover, the effect on the inhibition of colorectal cancer cells' bioenergetics has been evaluated. Results: Yarrow-PP exerted the highest antioxidant activity, even higher than the complete UAE-yarrow extract, meanwhile yarrow-Sep showed the highest anti-inflammatory activity, even higher than the complete UAE-yarrow extract. Interestingly, yarrow-Sep inhibited key lipid metabolic targets in CRC cells extensively shown to be implicated in cancer dissemination and prognosis -SREBF1, FASN, ABCA1 and HMGCR- and epithelial to mesenchymal targets-CDH1, ATP1B1, CDH2 and Vimentin-augmenting cell adhesion. Conclusions: In summary, SAS technology has been applied to provide a novel combination of bioactive compounds, yarrow-Sep, which merits further research to be proposed as a potential complementary nutraceutical in the treatment of CRC.

Supercritical Antisolvent Precipitation of Corticosteroids/β-Cyclodextrin Inclusion Complexes.

In this study, corticosteroid-β-cyclodextrin (β-CD) inclusion complexes were prepared by using supercritical antisolvent (SAS) precipitation to enhance the dissolution rate of dexamethasone (DEX) and prednisolone (PRED), which are poorly water soluble drugs. The processing of the active principles in the absence of a carrier led to their almost complete extraction (the small amount of obtained material precipitates in the form of crystals). The coprecipitation of the ingredients in the presence of β-CD was investigated at different concentrations, pressures, and molar ratios. For both the corticosteroids, the optimized operating conditions were 40 °C, 120 bar, an equimolar ratio, and a concentration in DMSO of 20 mg/mL; these conditions led to the attainment of microparticles with mean diameters equal to 0.197 ± 0.180 μm and 0.131 ± 0.070 μm in the case of DEX and PRED, respectively. Job's method confirmed the formation of inclusion complexes with a 1/1 mol/mol ratio. Compared to the pure ingredients, the obtained powders have an improved release rate, which is about three times faster in both cases. The release curves obtained under the best operating conditions were fitted using different models. The best fitting was obtained using the Weibull model, whose parameters are compatible with a combined release mechanism involving Fickian diffusion and controlled release.

Solubility of Malonic and Succinic Acids in CO2–Solvent Mixtures and Their Micronization by Supercritical Antisolvent Precipitation

Solubility of Malonic and Succinic Acids in CO2–Solvent Mixtures and Their Micronization by Supercritical Antisolvent Precipitation

Supercritical Antisolvent Precipitation of Levofloxacin Hydrochloride from a Single-Phase and a Two-Phase CO2–Dimethylformamide Mixture

Supercritical Antisolvent Precipitation of Levofloxacin Hydrochloride from a Single-Phase and a Two-Phase CO2–Dimethylformamide Mixture

Viscosity Measurement of CO2-Solvent Mixtures for the Study of the Morphology and Size of Crystalline Particles Obtained Using Supercritical Antisolvent Precipitation.

The viscosity values of CO2-dimethylphormamide, chloroform, methanol, isopropanol, ethyl acetate, acetone, and dimethyl sulfoxide mixtures were measured at a pressure of 150 bar and a temperature of 313 K. The correlation of the mean size of levofloxacin hydrochloride and malonic acid particles precipitated using the SAS method with the viscosity of the used CO2-solvent mixtures is shown. The high viscosity of the mixtures leads to slower mixing of the solution and the antisolvent. Therefore, crystallization occurs at large fractions of the solvent, and as a consequence at a lower supersaturation. This causes the formation of larger particles when using more viscous solvents in SAS.

Solubility measurement and modeling of hydroxychloroquine sulfate (antimalarial medication) in supercritical carbon dioxide

A supercritical fluid, such as supercritical carbon dioxide (scCO2) is increasingly used for the micronization of pharmaceuticals in the recent past. The role of scCO2 as a green solvent in supercritical fluid (SCF) process is decided by the solubility information of the pharmaceutical compound in scCO2. The commonly used SCF processes are the rapid expansion of supercritical solution (RESS) and supercritical antisolvent precipitation (SAS). To implement micronization process, solubility of pharmaceuticals in scCO2 is required. Present study is aimed at both measuring and modeling of solubilities of hydroxychloroquine sulfate (HCQS) in scCO2. Experiments were conducted at various conditions (P = 12 to 27 MPa and T = 308 to 338 K), for the first time. The measured solubilities were found to be ranging between (0.0304 × 10–4 and 0.1459 × 10–4) at 308 K, (0.0627 × 10–4 and 0.3158 × 10–4) at 318 K, (0.0982 × 10–4 and 0.4351 × 10–4) at 328 K, (0.1398 × 10–4 and 0.5515 × 10–4) at 338 K. To expand the usage of the data, various models were tested. For the modelling task existing models (Chrastil, reformulated Chrastil, Méndez-Santiago and Teja (MST), Bartle et al., Reddy-Garlapati, Sodeifian et al., models) and new set of solvate complex models were considered. Among the all models investigated Reddy-Garlapati and new solvate complex models are able to fit the data with the least error. Finally, the total and solvation enthalpies of HCQS in scCO2 were calculated with the help of model constants obtained from Chrastil, reformulated Chrastil and Bartle et al., models.

Synthesis of Fe-doped ZnO by supercritical antisolvent precipitation for the degradation of azo dyes under visible light

Supercritical antisolvent precipitation was used to obtain ZnO (undoped) and Fe-doped ZnO photocatalysts at different Fe/Zn molar ratio percentages (0.57, 0.75 and 0.84 mol%). Wide-angle X-ray diffraction showed the hexagonal wurtzite as the main crystalline phase of the cauliflower-like nanoparticle aggregations (observed from Field Emission Scanning Electron Microscopy) with a mean diameter of 54.5 nm for the pure ZnO nanoparticles and a higher mean diameter (in the range 109.1–121.5 nm) for Fe-doped ZnO nanoparticles. XRF confirmed the approximate Fe/Zn ratios (0.55, 0.77, 0.82 mol%). The band gap energy, derived from UV − Vis diffuse reflectance measurements decreased upon Fe doping with values ranging from 3.22 (ZnO) to 2.83 eV (0.57 mol%Fe). The photocatalytic activity results showed that the undoped ZnO photocatalyst completely removes color from an aqueous solution containing Acid Orange 7 dye (AO7) after 30 min of UV light irradiation. Whereas Fe-doped ZnO photocatalyst with 0.75 mol% Fe content (0.75Fe) exhibited the highest discoloration efficiency (52 %) and total organic carbon (TOC) removal efficiency (∼36 %) of AO7 after 180 min under visible light. Moreover, the main reactive oxygen species involved in the AO7 degradation were assessed with the optimized photocatalyst (0.75Fe) in presence of scavenger molecules. The experimental results revealed that positive holes and superoxide are responsible for target dye degradation under visible light.

A Brief Review of the Supercritical Antisolvent (SAS) Technique for the Preparation of Nanocatalysts to Be Used in Biodiesel Production

In an era where sustainability is becoming the main driving force for research and development, supercritical fluids-based techniques are presented as a very efficient alternative technology to conventional extraction, purification, and recrystallization processes. Supercritical antisolvent (SAS) precipitation is a novel technique that can replace liquid antisolvent precipitation techniques. Additionally, through the optimization of precipitation operating conditions, morphology, particle size, and particle size distribution of nanoparticles can be controlled. As an antisolvent, supercritical carbon dioxide (scCO2) is far more sustainable than its conventional liquid counterparts; not only does it have a critical point (304 K and 73.8 bar) on its phase diagram that allows for the precipitation processes to be developed so close to room temperature, but also its recovery and, consequently, the precipitated solute purification stage is considerably simpler. This technique can be used efficiently for preparing nanocatalysts to be used in biodiesel production processes.

Synthesis of Co-Ni Alloy Particles with the Structure of a Solid Substitution Solution by Precipitation in a Supercritical Carbon Dioxide.

Mixed Co-Ni bimetallic systems with the structure of a solid substitution solution have been synthesized using the supercritical antisolvent precipitation (SAS) method, which uses supercritical CO2 as an antisolvent. The systems obtained have been characterized in detail using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared (FTIR) spectroscopy, and magnetostatic measurements. It has been found that Co-enriched systems have a defective hexagonal close-packed (hcp) structure, which was described by a model which embedded cubic fragments of packaging into a hexagonal close-packed (hcp) structure. It has been shown that an increase in water content at the precipitation stage leads to a decrease in the size of cubic fragments and a more uniform distribution of them in Co-enriched systems. It has also been shown that mixed systems have the greatest coercivity in the line of samples. Ni-enriched bimetallic systems have a cubic close-packed (ccp) structure with modified crystal lattice parameters.

Micronization of Levofloxacin Hydrochloride by the Supercritical Antisolvent Precipitation Method from Single-Phase and Two-Phase CO2–Acetone Mixtures

Micronization of Levofloxacin Hydrochloride by the Supercritical Antisolvent Precipitation Method from Single-Phase and Two-Phase CO2–Acetone Mixtures

Partial oxidation of methane to syngas over SmCoO3-derived catalysts: the effect of the supercritical fluid assisted modification of the perovskite precursor

Syngas is crucial raw for the production of hydrogen-rich gas for green energy and for various petrochemical processes. Herein, we report the Syngas production via partial oxidation of methane (POM) on new SmCoO3-derived catalysts produced from simple individual precursor. Precursor modified by supercritical antisolvent precipitation (SAS) involving supercritical CO2 yields SmCoO3 with finer grains, and the catalytic activity of respective Co/Sm2O3 composite formed in situ during POM is considerably enchanced. This catalyst does not undergo coking, and provides CO and H2 yields of 75–88% for 55 h at 900 °C, thereby being the most efficient POM catalysts derived from non-substituted LnCoO3. Thus, the prospects of exploiting SAS modification of the precursor for SmCoO3 to enhance the catalytic activity of the daughter Co/Sm2O3 composites are demonstrated for the first time. Given the overall simplicity in production, studied Co/Sm2O3 composites can also be convenient systems for further development of POM catalysts.

Production of single-domain powders of europium iron garnet using supercritical fluid technology

• Controlled size powders of Eu 3 Fe 5 O 12 were obtained using SAS method; • Thermal decomposition stages of the obtained garnet precursors were considered; • Critical grain size for the transition to the single-domain state is 33 nm. In this work, nanosized precursors of the Eu 3 Fe 5 O 12 complex oxide – europium iron garnet – were prepared for the first time by the method of a supercritical antisolvent precipitation. It was shown that changing the synthesis parameters, namely, pressure, temperature, concentration of the initial solution and nozzle diameter, made it possible to obtain particles of controlled size from 20 to 80 nm. The obtained samples were characterized by a complex of physicochemical methods of analysis: IR spectroscopy, XRD, TG/DSC analysis, TEM. The main magnetic characteristics were obtained from powders annealed at 800 °C on a vibration magnetometer. The dependence of the magnetic characteristics on the grain size was established. The critical size of the transition to the single-domain state is 33 nm. The features of the garnet crystalline phase formation for samples with the smallest grain size and extended surface were revealed.

High-loaded Ni-based catalysts obtained via supercritical antisolvent coprecipitation in transfer hydrogenation of anisole: Influence of the support

Transfer hydrogenation of anisole in 2-PrOH has been studied as a model reaction for lignocellulose processing. The reaction was studied over high-loaded Ni-based catalysts synthesized via supercritical antisolvent precipitation of a Ni precursor and sols of four oxides: Al2O3, SiO2, TiO2, and ZrO2. It was demonstrated that the oxide support significantly affects the structure of the catalysts, their activity, and selectivity. The best performance in the transfer hydrodeoxygenation of anisole was shown by Ni supported on alumina at 250 °C, which was explained by the highest dispersion of Ni0 particles in this catalyst and by the highest concentration of acid centers.

Photocatalytic activity of Eu-doped ZnO prepared by supercritical antisolvent precipitation route: When defects become virtues

• Eu-doped ZnO at different Eu content were synthetized by SAS process. • Eu-doped ZnO provides novel defect sites and higher hydrophilicity. • Photocatalytic activity was assessed under UV light. • The optimal Eu content for crystal violet and ferulic acid degradation was 1 mol%. • A lower hydrophilicity induced a higher vanillin selectivity. The aim of this work is to determine the structural and optical properties of Eu-doped ZnO powders prepared by supercritical antisolvent precipitation route (SAS) and to correlate the physico-chemical features with the photocatalytic activity under UV light. Raman and EPR spectroscopy highlight the introduction of novel defects (mainly singly and doubly ionized oxygen vacancies, and oxygen interstitials) on the Eu-doped ZnO samples, which confer higher hydrophilicity to the doped samples with respect to bare ZnO, as evidenced by FT-IR analysis. Additionally, photoluminescence spectra show that the presence of Eu 3+ totally quenches the visible light emission typical of bare ZnO, which mainly results from the recombination of photogenerated holes at defective sites. The prepared samples were tested both for the photocatalytic degradation of crystal violet dye (CV) and for the partial oxidation of ferulic acid under UV irradiation. The photocatalytic activity results evidence of a higher ability of Eu-doped photocatalysts to degrade CV and ferulic acid, while higher selectivity values towards vanillin are obtained in the presence of bare ZnO. The higher activity of Eu-doped ZnO photocatalysts is linked to the stabilization of photogenerated holes and to their higher hydrophilicity, both brought by the generation of defective sites induced by the presence of Eu 3+ ions within the ZnO lattice.

Microencapsulation of Natural Food Antimicrobials: Methods and Applications

The global demand for safe and healthy food with minimal synthetic preservatives is continuously increasing. Some natural food antimicrobials with strong antimicrobial activity and low toxicity have been considered as alternatives for current commercial food preservatives. Nonetheless, these natural food antimicrobials are hardly applied directly to food products due to issues such as food flavor or bioavailability. Recent advances in microencapsulation technology have the potential to provide stable systems for these natural antibacterials, which can then be used directly in food matrices. In this review, we focus on the application of encapsulated natural antimicrobial agents, such as essential oils, plant extracts, bacteriocins, etc., as potential food preservatives to extend the shelf-life of food products. The advantages and drawbacks of the mainly used encapsulation methods, such as molecular inclusion, spray drying, coacervation, emulsification, supercritical antisolvent precipitation and liposome and alginate microbeads, are discussed. Meanwhile, the main current applications of encapsulated antimicrobials in various food products, such as meat, dairy and cereal products for controlling microbial growth, are presented.

Formation of Polymer-Carbon Nanotube Composites by Two-Step Supercritical Fluid Treatment.

An approach for polymer-carbon nanotube (CNT) composite preparation is proposed based on a two-step supercritical fluid treatment. The first step, rapid expansion of a suspension (RESS) of CNTs in supercritical carbon dioxide, is used to de-bundle CNTs in order to simplify their mixing with polymer in solution. The ability of RESS pre-treatment to de-bundle CNTs and to cause significant bulk volume expansion is demonstrated. The second step is the formation of polymer-CNT composite from solution via supercritical antisolvent (SAS) precipitation. SAS treatment allows avoiding CNT agglomeration during transition from a solution into solid state due to the high speed of phase transition. The combination of these two supercritical fluid methods allowed obtaining a polycarbonate-multiwalled carbon nanotube composite with tensile strength two times higher compared to the initial polymer and enhanced elasticity.

Analysis of the Stages of Yittrum Iron Garnet Formation from a Precursor Obtained by the Supercritical Antisolvent CO2 Precipitation Technique

Analysis of the Stages of Yittrum Iron Garnet Formation from a Precursor Obtained by the Supercritical Antisolvent CO2 Precipitation Technique

The supercritical antisolvent precipitation from a sustainable perspective: A Life Cycle Assessment

The life cycle assessment (LCA) of the production of polyvinylpyrrolidone (PVP)/prednisolone (PDS) powders obtained by supercritical antisolvent (SAS) precipitation was performed to direct the production with a view to greater environmental sustainability. A 180 mg tablet containing the therapeutic dose of PDS (30 mg) was chosen as the functional unit, to which the emissions to air, water, and soil were reported. The analysis conducted with the aid of the SimaPro 9.1.1 software using primary data obtained by an Italian processor showed that the steps most impacting the environmental categories under study are the stabilization of the operating conditions, the injection step, and the washing step. An improved scenario aimed at lowering the impacts of these steps without altering the product was proposed, and a reduction of the global impact equal to 85.8 % is attainable.

Photocatalytic degradation of atrazine under visible light using Gd-doped ZnO prepared by supercritical antisolvent precipitation route

Supercritical antisolvent precipitation route was employed for the first time to prepare Gd-doped ZnO photocatalysts to be tested in the photocatalytic degradation of atrazine under visible light. Physical-chemical characterization data show that the addition of Gd does not change the crystalline structure of ZnO and that Gd3+ ions are successfully introduced into the semiconductor lattice, leading to a decrease of band gap energy value and inducing the formation of oxygen vacancies inside the ZnO framework. The photocatalytic performances of the as-prepared samples are determined by analyzing the degradation of atrazine under visible light irradiation. The doped photocatalyst with a Gd loading of 0.7 mol% exhibits the highest photocatalytic activity under visible light irradiation compared to the other prepared photocatalysts. The possible reaction mechanism of the optimized photocatalyst is also discussed.