Isolation and purification of alkaloids from lotus leaves by ionic‐liquid‐modified high‐speed countercurrent chromatography

An effective high‐speed countercurrent chromatography method was successfully established by using ionic liquids as the modifier of the two‐phase solvent system. Adding a small amount of ionic liquids significantly shortens the separation time and improves the separation efficiency. The conditions of ionic‐liquid‐modified high‐speed countercurrent chromatography including solvent systems, types and content of added ionic liquids, and ionic liquids posttreatment were investigated. The established method was successfully applied to separate alkaloids from lotus leaves using a two‐phase solvent system composed of petroleum ether/ethyl acetate/methanol/water/[C₄mim][BF₄] (1:5:1:5:0.15, v/v/v/v/v). Four alkaloids pronuciferine (1.7 mg), N‐nornuciferine (4.3 mg), nuciferine (3.1 mg), and roemerine (2.1 mg) were obtained with the purities of 90.53, 92.25, 99.86, and 98.63%, respectively, from 100 mg crude extract of lotus leaves. The results indicated that the ionic‐liquid‐modified high‐speed countercurrent chromatography method was suitable for alkaloid separation from lotus leaves and would be a promising method for the separation of alkaloids from other natural products.     

Preparative isolation of flavonoid compounds from Oroxylum indicum by high‐speed counter‐current chromatography by using ionic liquids as the modifier of two‐phase solvent system

A preparative high‐speed counter‐current chromatography method for isolation and purification of flavonoid compounds from Oroxylum indicum was successfully established by using ionic liquids as the modifier of the two‐phase solvent system. Two flavonoid compounds including baicalein‐7‐O‐diglucoside and baicalein‐7‐O‐glucoside were purified from the crude extract of O. indicum by using ethyl acetate–water–[C₄mim][PF₆] (5:5:0.2, v/v) as two‐phase solvent system. 36.4 mg of baicalein‐7‐O‐diglucoside and 60.5 mg of baicalein‐7‐O‐glucoside were obtained from 120 mg of the crude extract. Their purities were 98.7 and 99.1%, respectively, as determined by HPLC area normalization method. The chemical structures of the isolated compounds were identified by ¹H‐NMR and ¹³C‐NMR.     

Aerobic and Electrochemical Oxidative Cross‐Dehydrogenative‐Coupling (CDC) Reaction in an Imidazolium‐Based Ionic Liquid

The ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [BMIm][BF₄] has demonstrated high efficiency when applied as a solvent in the oxidative nitro‐Mannich carbon? carbon bond formation. The copper‐catalyzed cross‐dehydrogenative coupling (CDC) between N‐phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF₄] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and β‐nitroamine product was investigated employing [BMIm][BF₄] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.     

Synthesis and application of a chiral ionic liquid functionalized β‐cyclodextrin as a chiral selector in capillary electrophoresis

A novel chiral ionic liquid functionalized β‐cyclodextrin, 6‐O‐2‐hydroxpropyltrimethylammonium‐β‐cyclodextrin tetrafluoroborate ([HPTMA‐β‐CD][BF₄]), was synthesized and used as a chiral selector in capillary electrophoresis. [HPTMA‐β‐CD][BF₄] not only increased the solubility in aqueous buffer in comparison with the parent compound, but also provided a stable reversal electroosmotic flow, and the enantioseparation of eight chiral drugs was examined in phosphate buffer containing [HPTMA‐β‐CD][BF₄] as the chiral selector. The effects of the [HPTMA‐β‐CD][BF₄] concentration and the background electrolyte pH were studied. Moreover, the chiral separation abilities of β‐CD and [HPTMA‐β‐CD][BF₄] were compared and possible mechanisms for the chiral recognition of [HPTMA‐β‐CD][BF₄] are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

pH‐Zone‐refining counter‐current chromatography for two new lipo‐alkaloids separated from refined alkaline extraction of Kusnezoff monkshood root

An efficient and refined method for the separation of six aconitine‐type alkaloids from the alkaline prepared “Kusnezoff monkshood root” was established. It is the first study that two new lipo‐alkaloids were successfully isolated from refined sample by pH‐zone‐refining counter‐current chromatography rather than synthetic method. It was of interest that a great deal of lipo‐alkaloids was produced in crude extract from the alkalization of “Kusnezoff monkshood root.” A refined sample method was proposed to enrich two types of alkaloids by liquid–liquid extraction, i.e. lipo‐alkaloids and monoester‐diterpenoid alkaloids. The pH‐zone‐refining counter‐current chromatography was performed with an optimized two‐phase solvent system composed of n‐hexane‐ethyl acetate–methanol–water (3:5:4:5, v/v), where upper organic phase was added to 3 mmol/L triethylamine as a retainer and lower aqueous mobile phase was added to 3 mmol/L hydrochloric acid as an eluter. As a result, six aconitum alkaloids, including two lipo‐alkaloids (8‐lino‐14‐benzoylaconine, 8‐pal‐14‐benzoylaconine), three monoester‐diterpenoid alkaloids (14‐benzoylmesaconine, 14‐benzoylaconine, beyzoyldeoxyaconine), and one aconine alkaloid (neoline) were acquired from the plant at the same time. The anti‐inflammatory activities of the two new lipo‐alkaloids were compared to the six alkaloids in vitro, in cyclo‐oxygen‐ase‐2 inhibition assays. The separation mechanism of six alkaloids by pH‐zone‐refining counter‐current chromatography was illustrated.     

Gas‐phase dissociation of ionic liquid aggregates studied by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation

Positive singly charged ionic liquid aggregates [(C_nmim)_m+1(BF₄)_m]⁺ (mim = 3‐methylimidazolium; n = 2, 4, 8 and 10) and [(C₄mim)_m+1(A)_m]⁺ (A = Cl⁻, BF₄⁻, PF₆⁻, CF₃SO₃⁻ and (CF₃SO₂)₂N⁻) were investigated by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation. The electrospray ionisation mass spectra (ESI‐MS) showed the formation of an aggregate with extra stability for m = 4 for all the ionic liquids with the exception of [C₄mim][CF₃SO₃]. ESI‐MS‐MS and breakdown curves of aggregate ions showed that their dissociation occurred by loss of neutral species ([C_nmim][A])_a with a ≥ 1. Variable‐energy collision induced dissociation of each aggregate from m = 1 to m = 8 for all the ionic liquids studied enabled the determination of E_{cm, 1/2} values, whose variation with m showed that the monomers were always kinetically much more stable than the larger aggregates, independently of the nature of cation and anion. The centre‐of‐mass energy values correlate well with literature data on ionic volumes and interaction and hydrogen bond energies. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of additives and post‐treatment on the thermoelectric performance of vapor‐phase polymerized PEDOT films

Vapor‐phase polymerization (VPP) is an important method for the fabrication of high‐quality conducting polymers, especially poly(3,4‐ethylenedioxythiophene) (PEDOT). In this work, the effects of additives and post‐treatment solvents on the thermoelectric (TE) performance of VPP‐PEDOT films were systematically investigated. The use of 1‐butyl‐3‐menthylinidazolium tetrafluoroborate ([BMIm][BF₄], an ionic liquid) was shown to significantly enhance the electrical conductivity of VPP‐PEDOT films compared with other additives. The VPP‐PEDOT film post‐treated with mixed ethylene glycol (EG)/[BMIm][BF₄] solvent displayed the high power factor of 45.3 μW m^?1 K^?2 which is 122% higher than that prepared without any additive or post‐treatment solvent, along with enhanced electrical conductivity and Seebeck coefficient. This work highlighted the superior effect of the [BMIm][BF₄] additive and the EG/[BMIm][BF₄] solvent post‐treatment on the TE performance of the VPP‐PEDOT film. These results should help with developing the VPP method to fabricate high‐performance PEDOT films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1738–1744     

Separation and purification of five alkaloids from Aconitum duclouxii by counter‐current chromatography

C₁₉‐diterpenoid alkaloids are the main components of Aconitum duclouxii Levl. The process of separation and purification of these compounds in previous studies was tedious and time consuming, requiring multiple chromatographic steps, thus resulted in low recovery and high cost. In the present work, five C₁₉‐diterpenoid alkaloids, namely, benzoylaconine ( 1 ), N‐deethylaconitine ( 2 ), aconitine ( 3 ), deoxyaconitine ( 4 ), and ducloudine A ( 5 ), were efficiently prepared from A. duclouxii Levl (Aconitum L.) by ethyl acetate extraction followed with counter‐current chromatography. In the process of separation, the critical conditions of counter‐current chromatography were optimized. The two‐phase solvent system composed of n‐hexane/ethyl acetate/methanol/water/NH₃·H₂O (25%) (1:1:1:1:0.1, v/v) was selected and 148.2 mg of 1 , 24.1 mg of 2 , 250.6 mg of 3 , 73.9 mg of 4, and 31.4 mg of 5 were obtained from 1 g total Aconitum alkaloids extract, respectively, in a single run within 4 h. Their purities were found to be 98.4, 97.2, 98.2, 96.8, and 96.6%, respectively, by ultra‐high performance liquid chromatography analysis. The presented separation and purification method was simple, fast, and efficient, and the obtained highly pure alkaloids are suitable for biochemical and toxicological investigation.     

Reverse ATRP process of acrylonitrile in the presence of ionic liquids

An ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C₄mim] [BF₄]), was first used as the solvent in azobisisobutyronitrile (AIBN)‐initiated reverse atom transfer radical polymerization (RATRP) of acrylonitrile with FeCl₃/succinic acid (SA) as the catalyst system. The polymerization in [C₄mim][BF₄] proceeded in a well‐controlled manner as evidenced by kinetic studies. Compared with the polymerization in bulk, the polymerization in [C₄mim][BF₄] not only showed the best control of molecular weight and its distribution but also provided rather rapid reaction rate with the ratio of [C₄mim][BF₄] at 200:1:2:4. The polymerization apparent activation energies in [C₄mim][BF₄] and bulk were calculated to be 48.2 and 55.7 kJ mol^?1, respectively. Polyacrylonitrile obtained was successfully used as a macroinitiator to proceed the chain extension polymerization in [C₄mim][BF₄] via a conventional ATRP process. [C₄mim][BF₄] and the catalyst system could be easily recycled and reused after simple purification and had no effect on the living nature of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2701–2707, 2008     

Separation of betacyanins from flowers of Amaranthus cruentus L. in a polar solvent system by high‐speed counter‐current chromatography

Betacyanin extract of Amaranthus cruentus L. flowers was fractionated by semi‐preparative high‐speed counter‐current chromatography in a highly polar solvent system: propan‐1‐ol/acetonitrile/(NH₄)₂SO_{4satd. soln}/H₂O (1.0:0.5:1.2:1.0, v/v/v/v) in tail‐to‐head mode with 76% retention of the stationary phase. The crude extract as well as the fractions containing betacyanins were analyzed by liquid chromatography with tandem mass spectrometry as well as by high‐resolution ion‐trap time‐of‐flight mass spectrometry detection technique for the molecular formulae and multi‐step fragmentation pattern elucidation. Four betacyanins; namely, amaranthin, betanin, 6′‐O‐formyl‐amaranthin, and 6′‐O‐malonyl‐amaranthin as well as their diastereomeric forms differing in the configuration of the C‐15 carbon atom were identified in the fractions. Amaranthin was the dominant pigment in the extract and was additionally analyzed by nuclear magnetic resonance correlation techniques after the counter‐current chromatographic and high‐performance liquid chromatographic isolation. Betacyanins were highly enriched during a single high‐speed counter‐current chromatographic step; therefore, the tentative identification of new compounds for the whole Amaranthaceae family, 6′‐O‐formyl‐amaranthin and 6′‐O‐malonyl‐amaranthin was possible. Different elution profiles of the pigments observed in the counter‐current chromatographic system in comparison to high‐performance liquid chromatography system confirm a complementarity of both the techniques especially in the separation of diastereomeric pairs of betacyanins.     

Semi‐preparative high‐speed counter‐current chromatography separation of alkaloids from embryo of the seed of Nelumbo nucifera Gaertn by pH‐gradient elution

A new high‐speed counter‐current chromatography method for semi‐preparative separation and purification of alkaloids from embryo of the seed of Nelumbo nucifera Gaertn was developed by using pH‐gradient elution mode. Diethyl ether was used as the stationary phase of the two‐phase solvent system and Na₂HPO₄/NaH₂PO₄ buffer solution with pH values of 7.5 and 7.2 in gradient mode as the mobile phase. Consequently, 33 mg of liensinine, 42 mg of isoliensinine, and 67 mg of neferine were obtained from 200 mg of crude extracts. The purities of them were all over 98% as determined by HPLC area normalization method, and the structures were identified by ¹H‐NMR and ¹³C‐NMR.     

Effect of Ionic Liquid Anion Type in the Performance of Solid Polymer Electrolytes Based on Poly(Vinylidene fluoride‐trifluoroethylene)

The effect of different anions within the ionic liquid in the characteristics of solid polymer electrolytes (SPEs) based on P(VDF‐TrFE) has been investigated. 1‐ethyl‐3‐methylimidazolium acetate, [C₂mim][OAc], 1‐ethyl‐3‐methylimidazolium triflate, [C₂mim][(CF₃SO₃)], 1‐ethyl‐3‐methylimidazolium lactate, [C₂mim][Lactate], 1‐ethyl‐3‐methylimidazolium thiocyanate, [C₂mim][SNC] and 1‐ethyl‐3‐methylimidazolium hydrogen sulfate [C₂mim][HSO₄] have been used in SPE prepared by solvent casting. The polymer phase, thermal and electrochemical properties of the SPE have been determined. The thermal and electrical properties of the SPEs strongly depend on the selected IL, as determined by their different interactions with the polymer matrix. The room temperature ionic conductivity increases in the following way for the different anions: [SNC]>[CF₃SO₃)]>[HSO₄]>[Lactate]>[OAc], which is mainly dependent on the viscosity of the ionic liquid.     

Effective on‐line high‐speed shear dispersing emulsifier technique coupled with high‐performance countercurrent chromatography method for simultaneous extraction and isolation of carotenoids from Lycium barbarum L. fruits

An efficient combination strategy based on high‐speed shear dispersing emulsifier technique and high‐performance countercurrent chromatography was developed for on‐line extraction and isolation of carotenoids from the fruits of Lycium barbarum. In this work, the high‐speed shear dispersing emulsifier technique has been employed to extract crude extracts using the upper phase of high‐performance countercurrent chromatography solvent system composed of n‐hexane?dichloromethane?acetonitrile (10:4:6.5, v/v) as the extraction solvent. At the separation stage, the high‐performance counter‐current chromatography process adopts elution–extrusion mode and the upper phase of the solvent system as stationary phase (reverse‐phase mode). As a result, three compounds including zeaxanthin, zeaxanthin monopalmitate, and zeaxanthin dipalmitate with purities of 89, 90, and 93% were successfully obtained in one extraction‐separation operation within 120 min. The targeted compounds were analyzed and identified by high‐performance liquid chromatography, mass spectrometry, and NMR spectroscopy. The results indicated that the present on‐line combination method could serve as a simple, rapid, and effective way to achieve weak polar and unstable compounds from natural products.     

Preparative separation and purification of liensinine,isoliensinine and neferine from seed embryo of Nelumbo nucifera GAERTN using high‐speed counter‐current chromatography

A preparative high‐speed counter‐current chromatography method for separation and purification of liensinine, isoliensinine and neferine from seed embryo of Nelumbo nucifera GAERTN was successfully established by using n‐hexane‐ethyl acetate‐methanol‐water (5:8:4:5, v/v, containing 0.5% NH₄OH) as the two‐phase solvent system. From 200 mg of crude extract, 18.4 mg of liensinine, 19.6 mg of isoliensinine and 58.4 mg of neferine were obtained with the purity of 96.8, 95.9, and 98.6%, respectively. The identification of the three alkaloids was performed with ¹H NMR and ¹³C NMR.     

Preparative isolation of neomangiferin and mangiferin from Rhizoma anemarrhenae by high‐speed countercurrent chromatography using ionic liquids as a two‐phase solvent system modifier

A preparative high‐speed countercurrent chromatography method for isolation and purification of neomangiferin and mangiferin from Rhizoma anemarrhenae was successfully established by using ionic liquids as the modifier of the two‐phase solvent system. Neomangiferin and mangiferin were purified from the crude extract of R. anemarrhenae by using ethyl acetate‐water‐[C₄mim][PF₆] (5:5:0.2 v/v) as two‐phase solvent system. In total, 22.5 mg of neomangiferin and 70.6 mg of mangiferin were obtained from 150 mg of the crude extract. The purities of neomangiferin and mangiferin were 97.2 and 98.1%, respectively, as determined by HPLC. The chemical structures of the isolated compounds were identified by ¹H‐NMR and ¹³C‐NMR.     

1‐Octanol/Water Partition Coefficients of 1Alkyl‐3‐methylimidazolium Chloride

The solubilities of 1alkyl‐3‐methylimidazolium chloride, [C_nmim][Cl], where n=4, 8, 10, and 12, in 1octanol and water have been measured by a dynamic method in the temperature range from 270 to 370 K. The solubility data was used to calculate the 1octanol/water partition coefficients as a function of temperature and alkyl substituent. The melting point, enthalpies of fusion, and enthalpies of solid–solid phase transitions were determined by differential scanning calorimetry, DSC. The solubility of [C_nmim][Cl], where n=10 or 12 in 1octanol is comparable and higher than that of [C₄mim][Cl] in 1octanol. Liquid 1n‐octyl‐3‐methylimidazolium chloride, [C₈mim][Cl], is not miscible with 1octanol and water, consequently, the liquid–liquid equilibrium, LLE was measured in this system. The differences between the solubilities in water for n=4 and 12 are shown only in α₁ and γ₁ solid crystalline phases. Additionally, the immiscibility region was observed for the higher concentration of [C₁₀mim][Cl] in water. The intermolecular solute–solvent interaction of 1butyl‐3‐methylimidazolium chloride with water is higher than for other 1alkyl‐3‐methylimidazolium chlorides. The data was correlated by means of the UNIQUAC ASM and two modified NRTL equations utilizing parameters derived from the solid–liquid equilibrium, SLE. The root‐mean‐square deviations of the solubility temperatures for all calculated data are from 1.8 to 7 K and depend on the particular equation used. In the calculations, the existence of two solid–solid first‐order phase transitions in [C₁₂mim][Cl] has also been taken into consideration. Experimental partition coefficients (log P) are negative at three temperatures; this is evidence for the possible use of these ionic liquids as green solvents.     

Combinative application of pH‐zone‐refining and conventional high‐speed counter‐current chromatography for preparative separation of caged polyprenylated xanthones from gamboge

An efficient method for the preparative separation of four structurally similar caged xanthones from the crude extracts of gamboge was established, which involves the combination of pH‐zone‐refining counter‐current chromatography and conventional high‐speed counter‐current chromatography for the first time. pH‐zone‐refining counter‐current chromatography was performed with the solvent system composed of n‐hexane/ethyl acetate/methanol/water (7:3:8:2, v/v/v/v), where 0.1% trifluoroacetic acid was added to the upper organic stationary phase as a retainer and 0.03% triethylamine was added to the aqueous mobile phase as an eluter. From 3.157 g of the crude extract, 1.134 g of gambogic acid, 180.5 mg of gambogenic acid and 572.9 mg of a mixture of two other caged polyprenylated xanthones were obtained. The mixture was further separated by conventional high‐speed counter‐current chromatography with a solvent system composed of n‐hexane/ethyl acetate/methanol/water (5:5:10:5, v/v/v/v) and n‐hexane/methyl tert‐butyl ether/acetonitrile/water (8:2:6:4,v/v/v/v), yielding 11.6 mg of isogambogenic acid and 10.4 mg of β‐morellic acid from 218.0 mg of the mixture, respectively. The purities of all four of the compounds were over 95%, as determined by high‐performance liquid chromatography, and the chemical structures of the four compounds were confirmed by electrospray ionization mass spectrometry and NMR spectroscopy. The combinative application of pH‐zone‐refining counter‐current chromatography and conventional high‐speed counter‐current chromatography shows great advantages in isolating and enriching the caged polyprenylated xanthones.     

Separation and purification of 9,10‐dihydrophenanthrenes and bibenzyls from Pholidota chinensis by high‐speed countercurrent chromatography

Stilbenoids are the main components of leaves and stems of Pholidota chinensis. In the present investigation, high‐speed counter‐current chromatography was used for the separation and purification of two classes of stilbenoids, namely, bibenzyls and 9,10‐dihydrophenanthrenes, on a preparative scale from whole plants of P. chinensis with different solvent systems after silica gel column chromatography fractionation. n‐Hexane/ethyl acetate/methanol/water (1.2:1:1:0.8, v/v/v/v) was selected as the optimum solvent system to purify 1‐(3,4,5‐trimethoxyphenyl)‐1′,2′‐ethanediol ( 1 ), coelonin ( 2 ), 3,4′‐dihydroxy‐5,5′‐dimethoxybibenzyl ( 3 ), and 2,?7‐?dihydroxy‐?3,?4,?6‐?trimethoxy‐?9,?10‐?dihydrophenanthrene ( 4 ). While 2,7‐dihydroxy‐3,4,6‐trimethoxy‐?9,?10‐?dihydrophenanthrene ( 5 ), batatasin III ( 6 ), orchinol ( 7 ), and 3′‐O‐methylbatatasin III ( 8 ) were purified by n‐hexane/ethyl acetate/methanol/water (1.6:0.8:1.2:0.4, v/v/v/v). After the high‐speed counter‐current chromatography isolation procedure, the purity of all compounds was over 94% assayed by ultra high performance liquid chromatography. The chemical structure identification of all compounds was carried out by mass spectrometry and ¹H and ¹³C NMR spectroscopy. To the best of our knowledge, the current investigation is the first study for the separation and purification of bibenzyls and 9,10‐dihydrophenanthrenes by high‐speed counter‐current chromatography from natural resources.     

First separation of four aromatic acids and two analogues with similar structures and polarities from Clematis akebioides by high‐speed counter‐current chromatography

In this paper, we report an efficient method by high‐speed counter‐current chromatography for the first separation of four aromatic acids and two analogs with similar structures and polarities from Clematis akebioides. First, the ethyl acetate extract was treated by silica gel column chromatography to enrich the target compounds. And then the fraction with target compounds were purified by high‐speed counter‐counter chromatography using a two‐phase solvent system consisting of chloroform/acetonitrile/water (10:6:4, v/v). The results showed high‐speed counter‐current chromatography could be a powerful technology for the separation of compounds with similar structures and polarities. Besides, it was found acetonitrile could be a good methanol substitute when a chloroform/methanol/water system could not provide a good separation factor. This study provides a reference for the separation of compounds from Clematis akebioides.     

Application of an efficient strategy based on liquid–liquid extraction,high‐speed counter‐current chromatography,and preparative HPLC for the rapid enrichment,separation, and purification of four anthraquinones from Rheum tanguticum

This study presents an efficient strategy based on liquid–liquid extraction, high‐speed counter‐current chromatography, and preparative HPLC for the rapid enrichment, separation, and purification of four anthraquinones from Rheum tanguticum. A new solvent system composed of petroleum ether/ethyl acetate/water (4:2:1, v/v/v) was developed for the liquid–liquid extraction of the crude extract from R. tanguticum. As a result, emodin, aloe‐emodin, physcion, and chrysophanol were greatly enriched in the organic layer. In addition, an efficient method was successfully established to separate and purify the above anthraquinones by high‐speed counter‐current chromatography and preparative HPLC. This study supplies a new alternative method for the rapid enrichment, separation, and purification of emodin, aloe‐emodin, physcione, and chrysophanol.