Application of Supercritical Carbon Dioxide for the Preparation of Drug-Cyclodextrin Inclusion Compounds

Inclusion complexes of drugs into cyclodextrins (CDs) can be obtained at the solid state by means of supercritical dioxide (SCCO₂). A successful inclusion with a yield >98.5% has been achieved with piroxicam and -CD. The temperature and the time of exposure to SCCO₂ have a significant effect on the inclusion yield while the pressure has a negative effect. However, there is a strong interaction between temperature and pressure and this interaction has a positive influence. The molar ratio piroxicam--CD and the addition of ternary alkaline agents were also found to be significant factors. The dissolution rate of the complexes formed using SCCO₂ was found to be significantly higher than that of the physical mixture. Inclusion complexes have also been obtained with miconazole treating mixtures of miconazole, CDs and citric acid by SCCO₂. This new technique of inclusion of poorly soluble drugs into CDs allows the preparation of solid complexes without using organic solvents and thus without residues.     

Focused microwave-assisted solvent extraction and HPLC determination of effective constituents in Eucommia ulmodies Oliv. (E. ulmodies)

A new focused microwave-assisted solvent extraction method using water as solvent has been developed for leaching geniposidic and chlorogenic acids from Eucommia ulmodies Oliv. The extraction procedures were optimized using a two indexes orthogonal experimental design and graphical analysis, by varying irradiation time, solvent volume, solvent composition and microwave power. The optimum extraction conditions were obtained: for geniposidic acid, 50% micorwave power, 40 s irradiation, and 80% (v/v) aqueous methanol as extraction solvent (20 ml g⁻¹ sample); and for chlorogenic acid, 50% micorwave power, 30 s irradiation, and 20% aqueous methanol (20 ml g⁻¹ sample). The composition of the extraction solvent was optimized and can be directly used as the mobile phase in the HPLC separation. Quantification of organic acids was done by HPLC at room temperature using Spherigel C₁₈ chromatographic column (, i.d. 5 μm), the methanol:water:acetic acid (20:80:1.0, v/v) mobile phase and UV detection at 240 nm. The R.S.D. of the extraction process for geniposidic and chlorogenic acid were 3.8 and 4.1%, respectively.     

Measurements of the solubilities of derivatized amino acids in supercritical carbon dioxide

The solubilities of phenylalanine and tyrosine in supercritical carbon dioxide (SCCO₂) were measured after derivatization as the N-acetyl amino acid ethyl ester, N-carbobenzoxy amino acid and N-acetyl amino acid. Using an SCCO₂ flow system, a measuring method of the saturated solubilities of the derivatized amino acids was established in which the contact height of the extraction cell, i.e. a packed column, is increased till the concentration of a derivatized amino acid at the exit of the cell reaches a plateau. The solubilities of N-acetyl phenylalanine ethyl ester (APEE) exceeded 0.001 mole fraction, which is higher than those of caffeine produced in industrial SCCO₂ processes. A possible way of separating the amino acid mixtures using polarity differences in different amino acid side chains was demonstrated using the solubility data of the N-acetyl-amino acid ethyl esters in SCCO₂, as the solubilities of APEE are higher than those of N-acetyl tyrosine ethyl ester by two orders of magnitude.     

Homogeneous and Heterogeneous Catalyzed Esterification of Acrylic Acid with Ethanol: Reaction Kinetics and Modeling

Kinetics of esterification of acrylic acid with ethanol in the presence of homogeneous (H₂SO₄, HCl, p‐TSA, HI) catalysts as well as heterogeneous catalysts (Dowex 50WX, Amberlyst 15) was studied. The effects and performance of these catalysts on the conversion of acrylic acid were evaluated. In the kinetics of homogeneous catalyzed reaction, both concentration and activity‐based model were employed. Activity coefficients were predicted by the Universal Functional group Contribution (UNIFAC) method to consider nonideal behavior of the liquid phase. The heterogeneous catalyzed reaction mechanisms were developed using Eley–Rideal theory. The model results were compared with the experimental results and were in good agreement. The temperature dependency of the constants, reaction enthalpy, and entropy, and activation energy were determined. The conversion of acrylic acid was obtained as 63.2%, 61.02%, 53.3%, 21.4%, 34.96%, and 14.84% for H₂SO₄, p‐TSA, HCl, HI, Dowex 50WX, and Amberlyst 15, respectively, under process temperature of 70°C, reactant molar ratio of 1:1, and catalyst concentration of 2% (v/v) for homogeneous and 2.17 g for heterogeneous catalyst. These outcomes provide an approach to understand the significant effect of each catalyst on the esterification kinetics of acrylic acid and ethanol.     

Optimization of microwave‐assisted extraction of protopine and allocryptopine from stems of Macleaya cordata (Willd) R. Br. using response surface methodology

The purpose of the research was to investigate the multiple response optimizations for the extraction of protopine and allocryptopine from the stems of Macleaya cordata (Willd) R. Br. by using microwave‐assisted extraction (MAE). A three‐level, three‐factor Box–Behnken design of response surface methodology was used to develop response model, and desirability function was employed to optimize the effects of main extraction parameters. Three variables, ethanol concentration (20–80%, v/v), extraction temperature (30–70°C) and solvent/solid ratio (10:1 to 30:1, mL/g), were investigated in this study. The results showed that the optimum parameters of MAE were ethanol concentration of 45.2 % (v/v), extraction temperature of 54.7°C and solvent/solid ratio of 20.4:1 (mL/g). Under these conditions, the extraction yields of protopine and allocryptopine were 89.4 and 102.0%, respectively, and the extracta sicca yield was 12.5%. The combination use of response surface methodology, Box‐Behnken design and the appropriate desirability function could provide an insight into a lab‐scale MAE process, and help to develop procedures for commercial production of active ingredients from medical plants.     

The determination of ethanol in wine by voltammetry with an internal standard

A rapid method for the electroanalysis of ethanol is presented that incorporates flow extraction at room temperature, with voltammetric detection and potassium ferrocyanide [K₄Fe(CN)₆] as internal standard. In 0.1 M NaOH electrolyte, ethanol was oxidised at a platinum comb-shaped working electrode at −300 mV (vs. a Ag/AgCl reference electrode) and K₄Fe(CN)₆ was oxidized at +180 mV. The ratio of the anodic peak currents was linear with ethanol concentration in the range of 0.1 to 8.0% (v./v.), and the detection limit (calculated as 3 σ background) was 0.012 % (v./v.) for Osteryoung square wave voltammetry (OSWV) and 0.023 %(v./v.) for cyclic voltammetry (CV). The average extraction efficiency of ethanol from aqueous solutions, at 20 ± 1°C, was 8.5%. The repeatability was in the range of 2.5 to 3.3% RSD (n = 8), and accuracy was in the range of 95.2 to 104.7% for the determination of wine samples. Application to wines compared well with GC and HPLC methods and the nominal ethanol concentration determined by gravimetry. Analytical parameters in CV and OSWV are optimized, and the dependence of the extraction efficiency with temperature and nitrogen gas flow is presented.     

Phenolic and flavonoid compounds extraction from Calophyllum inophyllum leaves

Calophyllum inophyllum has been known as a part of the mangrove forest area. This species is distributed primarily in the coastal regions of Indonesia and Africa. It is rich in bioactive compounds and has been used as a traditional medication. This work employed a single replicate of the one-factor-at-a-time experiment method to investigate optimum conditions, which resulted in the highest TPC. The three factors studied were organic solvent type (acetone, ethanol, and methanol), organic solvent concentration in water (50–100%, v/v), and extraction temperature (30–60 °C). The extraction was conducted with the percolation method. The result shows that organic solvent type, organic solvent concentration in water, and extraction temperature significantly affect the TPC, TFC, and the yield of crude extract obtained. The highest TPC (289.12 mg GAE/g of the residue of C. inophyllum leaves) was achieved with 80% methanol in water at 30 °C for 48 h. Under this condition, TFC value of 410.4 mg QE/g of the residue of C. inophyllum leaves, the yield of 2.41%, and IC₅₀ value of 0.054 µg/mL were achieved. Moreover, bis (2-ethylhexyl) phthalate was firstly detected in the extract.     

Determination and pharmacokinetics of geniposidic acid in rat plasma after oral administration of Gardenia jasminoides fruit crude extract and Zhi‐zi‐chi decoction

A simple and efficient liquid chromatography–mass spectrometry method was developed and validated for the determination of geniposidic acid in rat plasma. After the addition of internal standard salidroside and acidification (0.1% formic acid, pH = 3.2), plasma samples were carried out by protein precipitation with acetonitrile and separated on a Kromasil C₁₈ column (150 × 4.6 mm, 5 µm) within a run time of 9.0 min. Analysis was performed in selected ion monitoring mode with a positive electrospray ionization interface. No endogenous interference was observed at retention times of the analytes because of the high specificity of selected ion monitoring mode. The linear range was 0.02–4.0 µg/mL and the lower limit of quantification was 0.02 µg/mL. The mean extraction recoveries of geniposidic acid and internal standard from rat plasma were all >88.0% and the matrix effects were within acceptance criteria (90–110%). The validated method was successfully applied to the pharmacokinetic study of geniposidic acid in rat plasma after oral administration of G. jasminoides fruit crude extract and Zhi‐zi‐chi decoction, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

含CO2/离子液体系统相行为及其在反应与分离中的应用进展

目前已知的绿色溶剂主要包括超临界流体（Supercritical fluids,SCFs）、离子液体（Ionic liquids,ILs）、二氧化碳膨胀液体（CO₂ expanded liquids, CXLs）、水以及上述溶剂的混合物等。其中,由超临界CO₂（Supercritical CO₂,SCCO₂）与ILs混合而构成的新兴溶剂,因为化学热力学方面的特性,成为近年来研究的热点,未来很有发展前景。本文回顾了目前为止在该领域所开展的工作,总结了影响SCCO₂与IL相行为的主要因素。包括温度、压力、ILs的含水量、ILs的阴离子、ILs的阳离子、ILs的摩尔体积以及助溶剂等。同时分析了ILs/SCCO₂与溶质形成的多元混合物相行为的成因。介绍了ILs/CO₂在萃取、反萃取、膜分离、反胶束、萃取与反应耦合等分离方面的应用。由于传统的单元操作很难满足无污染和对过程集成的要求,因而含有ILs/ SCCO₂的分离反应耦合过程将是未来是实现清洁生产的发展方向。     

Effects of process parameters on supercritical CO2 extraction of total phenols from strawberry (Arbutus unedo L.) fruits: An optimization study

The aim of this work was to optimize total phenolic yield of Arbutus unedo fruits using supercritical fluid extraction. A Box–Behnken statistical design was used to evaluate the effect of various values of pressure (50–300 bar), temperature (30–80°C) and concentration of ethanol as co‐solvent (0–20%) by CO₂ flow rate of 15 g/min for 60 min. The most effective variable was co‐solvent ratio (p<0.005). Evaluative criteria for both dependent variables (total phenols and radical scavenging activity) in the model were assigned maximum. Optimum extraction conditions were elicited as 60 bar, 48°C and 19.7% yielding 25.72 mg gallic acid equivalent (GAE) total phenols/g extract and 99.9% radical scavenging capacity, which were higher than the values obtained by conventional water (24.89 mg/g; 83.8%) and ethanol (15.12 mg/g; 95.8%) extractions demonstrating challenges as a green separation process with improved product properties for industrial applications.     

Separation and purification of fructooligosaccharides on a zeolite fixed‐bed column

Fructooligosaccharides (FOS), a well‐known prebiotic product, are obtained by enzymatic synthesis and consist of a mixture of mono‐ and disaccharides. In this work, a methodology for their separation and purification was developed using a zeolite fixed‐bed column. The effects of column temperature (40–60°C), eluent flow rate (0.10–0.14 mL/min), injected to bed volume percent ratio (2.6–5.1%), and ethanol concentration in the eluent (40–60%, v/v) were investigated using a fractionary factorial design (2^4–1), having the separation efficiency and purity as target responses. Additional experiments were performed as well, where the temperature and ethanol concentration were studied in a central composite design (2²). In this work, the zeolite fixed‐bed column was shown to be a good alternative for FOS purification, allowing a FOS purity of 90% and separation efficiency of 6.86 between FOS and glucose, using an eluent at 45°C with 60% ethanol concentration.     

Ion‐pair cloud‐point extraction: A new method for the determination of water‐soluble vitamins in plasma and urine

A novel, simple, and effective ion‐pair cloud‐point extraction coupled with a gradient high‐performance liquid chromatography method was developed for determination of thiamine (vitamin B₁), niacinamide (vitamin B₃), pyridoxine (vitamin B₆), and riboflavin (vitamin B₂) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion‐pair formation approach between these ionizable analytes and 1‐heptanesulfonic acid sodium salt as an ion‐pairing agent. Influential variables on the ion‐pair cloud‐point extraction efficiency, such as the ion‐pairing agent concentration, ionic strength, pH, volume of Triton X‐100, extraction temperature, and incubation time have been fully evaluated and optimized. Water‐soluble vitamins were successfully extracted by 1‐heptanesulfonic acid sodium salt (0.2% w/v) as ion‐pairing agent with Triton X‐100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r² > 0.9916) and precision in the concentration ranges of 1‐50 μg/mL for thiamine and niacinamide, 5–100 μg/mL for pyridoxine, and 0.5–20 μg/mL for riboflavin. The recoveries were in the range of 78.0–88.0% with relative standard deviations ranging from 6.2 to 8.2%.     

Biosurfactant trehalose lipid‐enhanced ultrasound‐assisted micellar extraction and determination of the main antioxidant compounds from functional plant tea

Hydrosoluble trehalose lipid (a biosurfactant) was employed for the first time as a green extraction solution to extract the main antioxidant compounds (geniposidic acid, chlorogenic acid, caffeic acid, and rutin) from functional plant tea (Eucommia ulmoides leaves). Single‐factor tests and response surface methodology were employed to optimize the extraction conditions for ultrasound‐assisted micellar extraction combined with ultra‐high‐performance liquid chromatography in succession. A Box‐Behnken design (three‐level, three‐factorial) was used to determine the effects of extraction solvent concentration (1–5 mg/mL), extraction solvent volume (5–15 mL), and extraction time (20–40 min) at a uniform ultrasonic power and temperature. In consequence, the best analyte extraction yields could be attained when the trehalose lipid solution concentration was prepared at 3 mg/mL, the trehalose lipid solution volume was 10 mL and the extraction time was set to 35 min. In addition, the recoveries of the antioxidants from Eucommia ulmoides leaves analyzed by this analytical method ranged from 98.2 to 102%. These results indicated that biosurfactant‐enhanced ultrasound‐assisted micellar extraction coupled with a simple ultra‐high‐performance liquid chromatography method could be effectively applied in the extraction and analysis of antioxidants from Eucommia ulmoides leaf samples.     

Preparation of titanium dioxide nanostructure from ilmenite through sulfate-leaching process and solvent extraction by D<Subscript>2</Subscript>EHPA

In this study, TiO₂ nanoparticles have been obtained from low-grade ilmenite ore via two consecutive acid digestion and solvent extraction processes. The as-extracted TiO₂ (Anatase phase) product was characterized using techniques such as XRD, XRF, FESEM, FTIR and BET surface area. Diluted sulfuric acid and D₂EHPA (bis-(2-ethyl-hexyl) phosphoric acid) were used as digester agent and an extraction solvent, respectively. The effects of main parameters such as recycling capacities and D₂EHPA concentration, as well as the extraction time and temperature on TiO₂ extraction were investigated. The results demonstrated that the best performance and efficiency for titanium and total iron uptake were 99 and 3.8%, respectively, at the lowest concentration of D₂EHPA.     

Response surface optimization of ultrasound‐assisted flavonoids extraction from the flower of Citrus aurantium L. var. amara Engl

Citrus aurantium L. var. amara Engl is a member of genus Citrus (Rutaceae) and has been used in Chinese medicine with the effectiveness of digestant and expectorant. Ultrasonic‐assisted extraction process for maximum flavonoids from the flower of Citrus aurantium L. var. amara Engl was investigated by response surface methodology. Through single factor experiment, ranges of the main variables (including ethanol concentration, solid/liquid ratio, extraction time and temperature) affecting the extraction yield of flavonoids were confirmed. Box–Behnken central composite design consisting of 24 experimental runs and 5 replicates at zero point was then applied and a regress model was obtained to predict the optimal extraction yield. The ANOVA indicated that the regression equation fits very well with the actual situation, reflecting the relationship between the extraction yield of flavonoids and extraction conditions. The optimal conditions were as follows: extraction temperature 72.11°C, time 51.89 min, ethanol concentration 51.19% and liquid/solid ratio of 40:10. Under the optimal conditions, the maximum response value of yield (1.88%) was consistent with the experimental value (1.87%), indicating the feasibility and validation of response surface methodology in optimizing the extraction of flavonoids from the flower of Citrus aurantium L. var. amara Engl.     

Esterification activity and stability of Candida rugosa lipase immobilized into chitosan

Microbial lipase from Candida rugosa immobilized into porous chitosan beads was tested for esterification selectivity with butanol and different organic acids (C2–C12), and butyric acid and different aliphatic alcohols (C2–C10). After 24 h, the acids tested achieved conversions of about 40–45%. Acetic acid was the only exception, and in this case butanol was not consumed. Different alcohols led to butyric acid conversions >40%, except for ethanol, in which case butyric acid was converted only 26%. The system’s butanol and butyric acid were selected for a detailed study by employing an experimental design. The influence of temperature, initial catalyst concentration, and acid:alcohol molar ratio on the formation of butyl butyrate was simultaneously investigated, employing a 2³ full factorial design. The range studied was 37–50°C for temperature (X₁), 1.25–2.5% (w/v) for the catalyst concentration (X₂), and 1 and 2 for the acid:alcohol molar ratio (X₃). Catalyst concentration (X₂) was found to be the most significant factor and its influence was positive. Maximum ester yield (83%) could be obtained when working at the lowest level for temperature (37°C), highest level for lipase concentration (2.5% [w/v]), and center level of acid:alcohol molar ratio (1.5). The immobilized lipase was also used repeatedly in batch esterification reactions of butanol with butyric acid, revealing a half-life of 86 h.     

Effect of nutrient supplements addition on ethanol production from cheese whey usingCandida pseudotropicalis under batch condition

Candida pseudotropicalis ATCC 8619 was selected among nine strains of lactose fermenting yeast for the production of ethanol from cheese whey. The effects of three nutrients (ammonium sulfate (NH₄)₂SO₄, dipotassium hydrogen phosphate K₂HPO₄, yeast extract, and a combination of them) on the ethanol yield from cheese whey were investigated. The results indicated that no addition of nutrient supplement is necessary to achieve complete lactose utilization during the cheese whey ethanol fermentation. However, addition of a small concentration (0.005% w/v) of these supplements reduced the lag period and the total fermentation time and increased the specific growth rate of the yeast. Higher concentrations (0.01 and 0.015% w/v) of ammonium sulfate and dipotassium hydrogen phosphate inhibited the cell growth and reduced lactose consumption. The highest ethanol (21.17 g/L) was achieved using yeast extract at a concentration of 0.01% w/v, given a conversion efficiency of 98.3%. No indication of alcohol inhibition was observed in this study.     

Comparison of techniques for the extraction of the hypotensive drugs geniposidic acid and geniposide from Eucommia ulmoides

The extraction of geniposidic acid and geniposide from Eucommia ulmoides was carried out by Soxhlet extraction, enzyme-assisted aqueous extraction, semi-bionic extraction and supercritical fluid extraction techniques and the extracts were analyzed by high performance liquid chromatography. The results showed that the best methods for extraction of geniposidic acid and geniposide are enzyme-assisted aqueous extraction and semi-bionic extraction. Compared with various extraction methods, the semi-bionic extraction was more efficient, yielding the highest amount of geniposidic acid and geniposide. In semi-bionic extraction, no organic solvent was used. Semi-bionic extraction was performed at the same pH as that of the human body. The results indicated that semi-bionic extraction was the best method for large-scale efficient extraction of geniposidic acid and geniposide from plant materials. The supercritical fluid extraction process required more time than the other methods, and gave the lowest yields of geniposidic acid and geniposide.     

Simultaneous Determination of Five Major Biologically Active Ingredients in Different Parts of Gardenia jasminoides Fruits by HPLC with Diode-Array Detection

A simple, sensitive and specific HPLC method for the simultaneous separation and determination of geniposide, geniposidic acid, chlorogenic acid, crocin 1 and 2 in fruits of Gardenia jasminoides Ellis was developed. Optimum chromatographic performance was obtained with a C₁₈ column and acetonitrile—0.1% aqueous trifluoroacetic acid (v/v) as mobile phase. Isolated peaks were detected at 240 nm for geniposidic acid and geniposide, 330 nm for chlorogenic acid and 440 nm for crocin 1 and 2, respectively. Comparison of spectra recorded with a diode-array detector during elution of peaks enabled determination of method specificity. Quantitative determinations on different parts of gardenia fruit demonstrated that all these compounds were abundant mainly in pericarps and pulps and only iridoid glycosides were also presented in sepals and seeds of the fruits.     

Optimization of ultrasonic‐assisted extraction of phenolic antioxidants from Malus baccata (Linn.) Borkh. using response surface methodology

In this study, the optimum extraction conditions for maximum recovery of the content of total phenolics (TPC) and total antioxidant abilities were analyzed for Malus baccata (Linn.) Borkh. using response surface methodology. The effects of ethanol percentage (X₁,%), ultrasonic power (X₂, W) and extraction temperature (X₃, °C) on the total phenolic content (Y₁) and antioxidant ability (Y₂) were evaluated. A second‐order polynomial model produced a satisfactory fitting of the experimental data with regard to total phenolic content (R² = 0.9942, P < 0.0001) and antioxidant ability (R² = 0.9966, P < 0.0001). The optimized conditions were ethanol concentration of 61.0%, ultrasonic power of 308.6 W, extraction temperature of 51.1°C for TPC and 60.5%, 311.4 W, 51.6°C for antioxidant ability, the predicted values agreed well with the experimental values. Results implied that the major phenolic compounds in obtained extracts as chlorogenic acid, quercetin‐3‐gal/glu, quercetin‐3‐xyl/ara, phloretin‐2‐xyloside, quercetin‐3‐ rhamnoside, and phloridzin.