Shihua Wu | Zhejiang University (original) (raw)

Papers by Shihua Wu

Research paper thumbnail of RAGE expression in tumor-associated macrophages promotes angiogenesis in glioma

Cancer research, Jan 15, 2014

Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promot... more Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promote tumor progression, invasion, and angiogenesis. Although blocking RAGE signaling has been proposed as a potential anticancer strategy, functional contributions of RAGE expression in the tumor microenvironment (TME) have not been investigated in detail. Here, we evaluated the effect of genetic depletion of RAGE in TME on the growth of gliomas. In both invasive and noninvasive glioma models, animal survival was prolonged in RAGE knockout (Ager(-/-)) mice. However, the improvement in survival in Ager(-/-) mice was not due to changes in tumor growth rate but rather to a reduction in tumor-associated inflammation. Furthermore, RAGE ablation in the TME abrogated angiogenesis by downregulating the expression of proangiogenic factors, which prevented normal vessel formation, thereby generating a leaky vasculature. These alterations were most prominent in noninvasive gliomas, in which the expres...

Research paper thumbnail of Synthesis of arbutin by two-step reaction from glucose

Journal of Zhejiang University. Science, 2004

Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-alpha... more Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl chloride or bromide was prepared by glucose and acetyl halide (chloride or bromide). (b) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl halide (Cl, Br) reacted with hydroquinone, methanol as solvent at pH=9.5-10.0.

Research paper thumbnail of Preparation and characterization of CuO/CeO 2 catalysts and their applications in low-temperature CO oxidation

Applied Catalysis A-general, 2005

CeO2 nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supp... more CeO2 nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO2 catalysts prepared via the impregnation method. The samples were characterized by HRTEM, XRD, H2-TPR, and XPS. The catalytic properties of the prepared catalysts for low-temperature CO oxidation were studied by using a microreactor–GC system. The results showed that the thermal decomposition temperature affected

Research paper thumbnail of Porous ceria hollow microspheres: Synthesis and characterization

Microporous and Mesoporous Materials, 2009

Porous hollow microspheres of crystalline ceria were synthesized via a simple carbon sphere templ... more Porous hollow microspheres of crystalline ceria were synthesized via a simple carbon sphere template method. The as-synthesized products were characterized by techniques of XRD, XPS, SEM, TEM and N2 adsorption–desorption. Structural characterization indicated that as-prepared ceria hollow microspheres (150nm in diameter) possess porous structure (average pore diameter of 6.5nm), high surface area (144.1m2/g), large pore volume (0.23cm3g−1) and thin shell

Research paper thumbnail of Separation and characterization of clindamycin and related impurities in bulk drug by high-performance liquid chromatography-electrospray tandem mass spectrometry

Journal of Pharmaceutical and Biomedical Analysis, 2006

A simple high-performance liquid-electrospray ionization tandem mass spectrometric (HPLC-ESI-MSn)... more A simple high-performance liquid-electrospray ionization tandem mass spectrometric (HPLC-ESI-MSn) method has been developed for the rapid identification of clindamycin and its related minor impurities in bulk drug. The ESI-MSn results obtained allowed us to propose plausible schemes for their fragmentations, which were confirmed further by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) using collision-induced dissociation (CID) method at high mass resolution. The positive ESI-MS/MS of clindamycin and its derivative compounds showed some diagnostic fragments, such as the neutral losses of H2O, HCl, methanethiol and 2-methylthio-ethenol, and the residue of 3-propyl-N-methylpyrrolidine and 3-ethyl-N-methylpyrrolidine, which are specific and useful for the identification of the lincosamide antibiotics and related impurities. According to the fragmentation mechanism of mass spectrometry and HPLC-UV-ESI-MSn data, six impurities of clindamycin have been identified on-line. Additionally, the positive ion mode extracted ion current (EIC) method has been used to separate and identify these lincosamide compounds.

Research paper thumbnail of Effect of Addition of Base on Ceria and Reactivity of CuO/CeO2 Catalysts for Low-Temperature CO Oxidation

Journal of Natural Gas Chemistry, 2007

ABSTRACT: In this work, we have reported the influence of the addition of base (KOH) on the physi... more ABSTRACT: In this work, we have reported the influence of the addition of base (KOH) on the physic-ochemical property of ceria synthesized by alcohothermal process, and the alcohothermal mechanism was also put forward. Furthermore, the prepared CeO2 was ...

Research paper thumbnail of Characterization and catalytic performance of TiO2 nanotubes-supported gold and copper particles

Journal of Molecular Catalysis A: Chemical, 2006

TiO2 nanotubes are prepared via the reaction of anatase TiO2 powder with NaOH solution. Gold and ... more TiO2 nanotubes are prepared via the reaction of anatase TiO2 powder with NaOH solution. Gold and gold–copper supported on TiO2 nanotubes (Au/TiO2 NTs and Au–Cu/TiO2 NTs) are synthesized by deposition–precipitation method. The prepared materials are characterized with BET, powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Their catalytic performance for low-temperature CO oxidation is

Research paper thumbnail of Preparative isolation and purification of celastrol from Celastrus orbiculatus Thunb. by a new counter-current chromatography method with an upright coil planet centrifuge

Journal of Chromatography A, 2004

A new counter-current chromatography (CCC) method with an upright coil planet centrifuge, which h... more A new counter-current chromatography (CCC) method with an upright coil planet centrifuge, which holds four identical multilayer coil columns in the symmetrical positions around the centrifuge axis, was applied to the isolation and purification of celastrol from the roots of Celastrus orbiculatus Thunb. The crude celastrol was obtained by elution with light petroleum from ethanol extracts using 15 cm x 5 cm i.d. silica gel flash chromatography. Preparative CCC with a two-phase system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v) was successfully performed, yielding 798 mg celastrol at 99.5% purity from 1020 mg of the crude sample in one step separation.

Research paper thumbnail of Preparative counter-current chromatography isolation of liensinine and its analogues from embryo of the seed of Nelumbo nucifera GAERTN. using upright coil planet centrifuge with four multilayer coils connected in series

Journal of Chromatography A, 2004

Preparative counter-current chromatography (CCC) isolation of liensinine and its analogues, isoli... more Preparative counter-current chromatography (CCC) isolation of liensinine and its analogues, isoliensinine and neferine from embryo of the seed of Nelumbo nucifera GAERTN. has been successfully performed for the first time using upright coil planet centrifuge with four multilayer coils connected in series with 1600 mL capacity. Two kinds of two-phase solvent systems were applied to preparative CCC isolation. The first was the system composed of light petroleum (b.p. 60-90 degrees C)-ethyl acetate-tetrachloromethane-chloroform-methanol-water (1:1:4:4:6:2, v/v) which was very suitable for fast and small-scale CCC isolation. The second was the system composed of ethyl acetate-tetrachloromethane-methanol-water (1:6:4:1, v/v), which was the optimum for large-scale CCC isolation. Using the first system, 1102 mg of the crude alkaloid was purified in one-step separation of 150 min, yielding 350 mg neferine, 100 mg isoliensinine and 95 mg liensinine with over 95% purity. While using the second solvent system, 5850 mg of the crude alkaloid was purified in one-step separation of 9 h, yielding 2545 mg neferine, 698 mg isoliensinine and 650 mg liensinine with over 97% purity. Structures of the compounds were identified by electrospray ionization multiple mass spectrometry, one- and two-dimensional NMR.

Research paper thumbnail of Preparative counter-current chromatography purification of valrubicin (AD-32) from crude synthetic drug using upright coil planet centrifuge with four multilayer coils connected in series

Journal of Chromatography A, 2005

Research paper thumbnail of Multi-channel counter-current chromatography for high-throughput fractionation of natural products for drug discovery

Journal of Chromatography A, 2008

A multi-channel counter-current chromatography (CCC) method has been designed and fabricated for ... more A multi-channel counter-current chromatography (CCC) method has been designed and fabricated for the high-throughput fractionation of natural products without complications sometimes encountered with other conventional chromatographic systems, such as irreversible adsorptive constituent losses and deactivation, tailing of solute peaks and contamination. It has multiple independent CCC channels and each channel connects independent separation column(s) by parallel flow tubes, and thus the multi-channel CCC apparatus can achieve simultaneously two or more independent chromatographic processes. Furthermore, a high-throughput CCC fractionation method for natural products has been developed by a combination of a new three-channel CCC apparatus and conventional parallel chromatographic devices including pumps, sample injectors, effluent detectors and collectors, and its performance has been displayed on the fractionation of ethyl acetate extracts of three natural materials Solidago canadensis, Suillus placidus, and Trichosanthes kirilowii, which are found to be potent cytotoxic to tumor cell lines in the course of screening the antitumor candidates. By combination of biological screening programs and preparative high-performance liquid chromatography (HPLC) purification, 22.8 mg 6 beta-angeloyloxykolavenic acid and 29.4 mg 6 beta-tigloyloxykolavenic acid for S. canadensis, 25.3mg suillin for S. placidus, and 6.8 mg 23,24-dihydrocucurbitacin B for T. Kirilowii as their major cytotoxic principles were isolated from each 1000 mg crude ethyl acetate extract. Their chemical structures were characterized by electrospray ionization mass spectrometry, one- and two-dimensional nuclear magnetic resonance. The overall results indicate the multi-channel CCC is very useful for high-throughput fractionation of natural products for drug discovery in spite of the solvent balancing requirement and the lower resolution of the shorter CCC columns.

Research paper thumbnail of Effect of gravitational force on type-J counter-current chromatography by mathematical analysis

Journal of Chromatography A, 2006

The gravitational force exerts an important effect on the counter-current chromatography (CCC) an... more The gravitational force exerts an important effect on the counter-current chromatography (CCC) and has been used to retain the stationary phase and improve the efficiency in the various CCC separations. This paper deals with the effect of gravitational force on type-J CCC, one of the most popular CCC methods by the mathematical analysis for the first time. The theoretical analyses reveal a close relationship between the effect of gravitational force, the placed orientation of type-J CCC apparatus, and the revolutional speed. Two placed orientations are more suitable for preparative CCC separation: one is common horizontal, and the other upright. Thus, there are three optimum conditions for type-J CCC separation, the first using horizontal apparatus at very low revolutional speed around 10rpm in the gravitational filed, the second by use of upright apparatus at moderate revolutional speed around 100rpm in the three-dimensional complex force field composed of centrifugal and orthogonal gravitational force, and the third employing the apparatus placed at any orientation including horizontal and upright CCC apparatus at high revolutional speed above 300rpm in the centrifugal force field. Therefore, we should consider the effect of gravitation force on CCC at the selection of proper operational conditions according to properties of two immiscible phases, the desired revolutional speed and the parameters of apparatus in order to utilize efficiently the effect of gravitational force. These analyses and results will benefit to improve the efficiency of CCC separation, especially large-scale industrial preparation.

Research paper thumbnail of Preparative isolation and purification of amides from the fruits of Piper longum L. by upright counter-current chromatography and reversed-phase liquid chromatography

Journal of Chromatography A, 2004

A versatile counter-current chromatography (CCC) with upright type-J multilayer coil planet centr... more A versatile counter-current chromatography (CCC) with upright type-J multilayer coil planet centrifuge, named upright CCC, was applied to the isolation and purification of amides from Piper longum L., which is widely used as an anodyne and a treatment for stomach disease in China. After the saponification by KOH of the ethanol extracts solution of 15 kg of crude drug "Piper Longi Fructus", the fruits of P. longum L., the solution was extracted with light petroleum and 500 g of red crude oil was obtained. Using 2.5 g of red crude oil as sample, the preparative upright CCC with a two-phase system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v) was successfully performed, which yielded nine fractions. Then these fractions were further purified by use of reversed-phase liquid chromatography (RPLC) with a glass column of 500 x 10 mm i.d. packed with reversed-phase silica gel. As a result, nine target amides with over 95% purity, i.e., 50 mg of (2E,4E)-N-isobutyl-eicosa-2,4-dienamide, 150 mg of (2E,4E,14Z)-N-isobutyl-eicosa-2,4,14-trienamide, 110 mg of (2E,4E,12Z)-N-isobutyl-ocatadeca-2,4,12-trienamide, 50 mg of guineensine, 60 mg of pipernonaline, 75 mg of pellitorine, 63 mg of piperine, 45 mg of piperanine, and 40 mg of piperlonguminine were isolated, respectively. Structures of all compounds were identified by electrospray ionization MS, electron impact ionization MS, one- and two-dimensional NMR spectra.

Research paper thumbnail of Comparing two models of gradient elution in counter-current chromatography

Journal of Chromatography A, 2013

Gradient change of mobile phase composition is commonly used in liquid chromatography to shorten ... more Gradient change of mobile phase composition is commonly used in liquid chromatography to shorten analysis duration. Gradient elution is possible in counter-current chromatography if it is demonstrated that the mobile phase composition changes are not associated with liquid stationary phase composition changes. Also, the solute distribution ratios in initial (1) and final (2) eluting systems must be known. If the solute distribution ratios during the changing mobile phase composition are modeled, the full gradient separation can be modeled using classical equations of liquid chromatography. Another approach allowed modeling empirically the gradient step. It considered the decreasing volume of mobile phase 1 and the increasing volume of mobile phase 2 used at each gradient time to derive a very simple equation. The two equations were compared computing the retention volumes of five test solutes. A remarkable agreement was observed considering the very different mathematical expressions of the two models. The step-gradient method was also modeled and its results compared to those of the linear gradient method.

Research paper thumbnail of Comparative Study on Catalytic Performances for Low-temperature CO Oxidation of Cu–Ce–O and Cu–Co–Ce–O Catalysts

Research paper thumbnail of The preparation and catalytic behavior of copper–cerium oxide catalysts for low-temperature carbon monoxide oxidation

Applied Catalysis A: General, 2005

Research paper thumbnail of Glycine-assisted hydrothermal synthesis of peculiar porous α-Fe2O3 nanospheres with excellent gas-sensing properties

Analytica Chimica Acta, 2010

Research paper thumbnail of Modeling gradient elution in countercurrent chromatography: Efficient separation of tanshinones from Salvia miltiorrhizaBunge

Journal of Separation Science, 2012

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifu... more Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.

Research paper thumbnail of RAGE expression in tumor-associated macrophages promotes angiogenesis in glioma

Cancer research, Jan 15, 2014

Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promot... more Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promote tumor progression, invasion, and angiogenesis. Although blocking RAGE signaling has been proposed as a potential anticancer strategy, functional contributions of RAGE expression in the tumor microenvironment (TME) have not been investigated in detail. Here, we evaluated the effect of genetic depletion of RAGE in TME on the growth of gliomas. In both invasive and noninvasive glioma models, animal survival was prolonged in RAGE knockout (Ager(-/-)) mice. However, the improvement in survival in Ager(-/-) mice was not due to changes in tumor growth rate but rather to a reduction in tumor-associated inflammation. Furthermore, RAGE ablation in the TME abrogated angiogenesis by downregulating the expression of proangiogenic factors, which prevented normal vessel formation, thereby generating a leaky vasculature. These alterations were most prominent in noninvasive gliomas, in which the expres...

Research paper thumbnail of Synthesis of arbutin by two-step reaction from glucose

Journal of Zhejiang University. Science, 2004

Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-alpha... more Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl chloride or bromide was prepared by glucose and acetyl halide (chloride or bromide). (b) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl halide (Cl, Br) reacted with hydroquinone, methanol as solvent at pH=9.5-10.0.

Research paper thumbnail of Preparation and characterization of CuO/CeO 2 catalysts and their applications in low-temperature CO oxidation

Applied Catalysis A-general, 2005

CeO2 nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supp... more CeO2 nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO2 catalysts prepared via the impregnation method. The samples were characterized by HRTEM, XRD, H2-TPR, and XPS. The catalytic properties of the prepared catalysts for low-temperature CO oxidation were studied by using a microreactor–GC system. The results showed that the thermal decomposition temperature affected

Research paper thumbnail of Porous ceria hollow microspheres: Synthesis and characterization

Microporous and Mesoporous Materials, 2009

Porous hollow microspheres of crystalline ceria were synthesized via a simple carbon sphere templ... more Porous hollow microspheres of crystalline ceria were synthesized via a simple carbon sphere template method. The as-synthesized products were characterized by techniques of XRD, XPS, SEM, TEM and N2 adsorption–desorption. Structural characterization indicated that as-prepared ceria hollow microspheres (150nm in diameter) possess porous structure (average pore diameter of 6.5nm), high surface area (144.1m2/g), large pore volume (0.23cm3g−1) and thin shell

Research paper thumbnail of Separation and characterization of clindamycin and related impurities in bulk drug by high-performance liquid chromatography-electrospray tandem mass spectrometry

Journal of Pharmaceutical and Biomedical Analysis, 2006

A simple high-performance liquid-electrospray ionization tandem mass spectrometric (HPLC-ESI-MSn)... more A simple high-performance liquid-electrospray ionization tandem mass spectrometric (HPLC-ESI-MSn) method has been developed for the rapid identification of clindamycin and its related minor impurities in bulk drug. The ESI-MSn results obtained allowed us to propose plausible schemes for their fragmentations, which were confirmed further by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) using collision-induced dissociation (CID) method at high mass resolution. The positive ESI-MS/MS of clindamycin and its derivative compounds showed some diagnostic fragments, such as the neutral losses of H2O, HCl, methanethiol and 2-methylthio-ethenol, and the residue of 3-propyl-N-methylpyrrolidine and 3-ethyl-N-methylpyrrolidine, which are specific and useful for the identification of the lincosamide antibiotics and related impurities. According to the fragmentation mechanism of mass spectrometry and HPLC-UV-ESI-MSn data, six impurities of clindamycin have been identified on-line. Additionally, the positive ion mode extracted ion current (EIC) method has been used to separate and identify these lincosamide compounds.

Research paper thumbnail of Effect of Addition of Base on Ceria and Reactivity of CuO/CeO2 Catalysts for Low-Temperature CO Oxidation

Journal of Natural Gas Chemistry, 2007

ABSTRACT: In this work, we have reported the influence of the addition of base (KOH) on the physi... more ABSTRACT: In this work, we have reported the influence of the addition of base (KOH) on the physic-ochemical property of ceria synthesized by alcohothermal process, and the alcohothermal mechanism was also put forward. Furthermore, the prepared CeO2 was ...

Research paper thumbnail of Characterization and catalytic performance of TiO2 nanotubes-supported gold and copper particles

Journal of Molecular Catalysis A: Chemical, 2006

TiO2 nanotubes are prepared via the reaction of anatase TiO2 powder with NaOH solution. Gold and ... more TiO2 nanotubes are prepared via the reaction of anatase TiO2 powder with NaOH solution. Gold and gold–copper supported on TiO2 nanotubes (Au/TiO2 NTs and Au–Cu/TiO2 NTs) are synthesized by deposition–precipitation method. The prepared materials are characterized with BET, powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Their catalytic performance for low-temperature CO oxidation is

Research paper thumbnail of Preparative isolation and purification of celastrol from Celastrus orbiculatus Thunb. by a new counter-current chromatography method with an upright coil planet centrifuge

Journal of Chromatography A, 2004

A new counter-current chromatography (CCC) method with an upright coil planet centrifuge, which h... more A new counter-current chromatography (CCC) method with an upright coil planet centrifuge, which holds four identical multilayer coil columns in the symmetrical positions around the centrifuge axis, was applied to the isolation and purification of celastrol from the roots of Celastrus orbiculatus Thunb. The crude celastrol was obtained by elution with light petroleum from ethanol extracts using 15 cm x 5 cm i.d. silica gel flash chromatography. Preparative CCC with a two-phase system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v) was successfully performed, yielding 798 mg celastrol at 99.5% purity from 1020 mg of the crude sample in one step separation.

Research paper thumbnail of Preparative counter-current chromatography isolation of liensinine and its analogues from embryo of the seed of Nelumbo nucifera GAERTN. using upright coil planet centrifuge with four multilayer coils connected in series

Journal of Chromatography A, 2004

Preparative counter-current chromatography (CCC) isolation of liensinine and its analogues, isoli... more Preparative counter-current chromatography (CCC) isolation of liensinine and its analogues, isoliensinine and neferine from embryo of the seed of Nelumbo nucifera GAERTN. has been successfully performed for the first time using upright coil planet centrifuge with four multilayer coils connected in series with 1600 mL capacity. Two kinds of two-phase solvent systems were applied to preparative CCC isolation. The first was the system composed of light petroleum (b.p. 60-90 degrees C)-ethyl acetate-tetrachloromethane-chloroform-methanol-water (1:1:4:4:6:2, v/v) which was very suitable for fast and small-scale CCC isolation. The second was the system composed of ethyl acetate-tetrachloromethane-methanol-water (1:6:4:1, v/v), which was the optimum for large-scale CCC isolation. Using the first system, 1102 mg of the crude alkaloid was purified in one-step separation of 150 min, yielding 350 mg neferine, 100 mg isoliensinine and 95 mg liensinine with over 95% purity. While using the second solvent system, 5850 mg of the crude alkaloid was purified in one-step separation of 9 h, yielding 2545 mg neferine, 698 mg isoliensinine and 650 mg liensinine with over 97% purity. Structures of the compounds were identified by electrospray ionization multiple mass spectrometry, one- and two-dimensional NMR.

Research paper thumbnail of Preparative counter-current chromatography purification of valrubicin (AD-32) from crude synthetic drug using upright coil planet centrifuge with four multilayer coils connected in series

Journal of Chromatography A, 2005

Research paper thumbnail of Multi-channel counter-current chromatography for high-throughput fractionation of natural products for drug discovery

Journal of Chromatography A, 2008

A multi-channel counter-current chromatography (CCC) method has been designed and fabricated for ... more A multi-channel counter-current chromatography (CCC) method has been designed and fabricated for the high-throughput fractionation of natural products without complications sometimes encountered with other conventional chromatographic systems, such as irreversible adsorptive constituent losses and deactivation, tailing of solute peaks and contamination. It has multiple independent CCC channels and each channel connects independent separation column(s) by parallel flow tubes, and thus the multi-channel CCC apparatus can achieve simultaneously two or more independent chromatographic processes. Furthermore, a high-throughput CCC fractionation method for natural products has been developed by a combination of a new three-channel CCC apparatus and conventional parallel chromatographic devices including pumps, sample injectors, effluent detectors and collectors, and its performance has been displayed on the fractionation of ethyl acetate extracts of three natural materials Solidago canadensis, Suillus placidus, and Trichosanthes kirilowii, which are found to be potent cytotoxic to tumor cell lines in the course of screening the antitumor candidates. By combination of biological screening programs and preparative high-performance liquid chromatography (HPLC) purification, 22.8 mg 6 beta-angeloyloxykolavenic acid and 29.4 mg 6 beta-tigloyloxykolavenic acid for S. canadensis, 25.3mg suillin for S. placidus, and 6.8 mg 23,24-dihydrocucurbitacin B for T. Kirilowii as their major cytotoxic principles were isolated from each 1000 mg crude ethyl acetate extract. Their chemical structures were characterized by electrospray ionization mass spectrometry, one- and two-dimensional nuclear magnetic resonance. The overall results indicate the multi-channel CCC is very useful for high-throughput fractionation of natural products for drug discovery in spite of the solvent balancing requirement and the lower resolution of the shorter CCC columns.

Research paper thumbnail of Effect of gravitational force on type-J counter-current chromatography by mathematical analysis

Journal of Chromatography A, 2006

The gravitational force exerts an important effect on the counter-current chromatography (CCC) an... more The gravitational force exerts an important effect on the counter-current chromatography (CCC) and has been used to retain the stationary phase and improve the efficiency in the various CCC separations. This paper deals with the effect of gravitational force on type-J CCC, one of the most popular CCC methods by the mathematical analysis for the first time. The theoretical analyses reveal a close relationship between the effect of gravitational force, the placed orientation of type-J CCC apparatus, and the revolutional speed. Two placed orientations are more suitable for preparative CCC separation: one is common horizontal, and the other upright. Thus, there are three optimum conditions for type-J CCC separation, the first using horizontal apparatus at very low revolutional speed around 10rpm in the gravitational filed, the second by use of upright apparatus at moderate revolutional speed around 100rpm in the three-dimensional complex force field composed of centrifugal and orthogonal gravitational force, and the third employing the apparatus placed at any orientation including horizontal and upright CCC apparatus at high revolutional speed above 300rpm in the centrifugal force field. Therefore, we should consider the effect of gravitation force on CCC at the selection of proper operational conditions according to properties of two immiscible phases, the desired revolutional speed and the parameters of apparatus in order to utilize efficiently the effect of gravitational force. These analyses and results will benefit to improve the efficiency of CCC separation, especially large-scale industrial preparation.

Research paper thumbnail of Preparative isolation and purification of amides from the fruits of Piper longum L. by upright counter-current chromatography and reversed-phase liquid chromatography

Journal of Chromatography A, 2004

A versatile counter-current chromatography (CCC) with upright type-J multilayer coil planet centr... more A versatile counter-current chromatography (CCC) with upright type-J multilayer coil planet centrifuge, named upright CCC, was applied to the isolation and purification of amides from Piper longum L., which is widely used as an anodyne and a treatment for stomach disease in China. After the saponification by KOH of the ethanol extracts solution of 15 kg of crude drug "Piper Longi Fructus", the fruits of P. longum L., the solution was extracted with light petroleum and 500 g of red crude oil was obtained. Using 2.5 g of red crude oil as sample, the preparative upright CCC with a two-phase system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v) was successfully performed, which yielded nine fractions. Then these fractions were further purified by use of reversed-phase liquid chromatography (RPLC) with a glass column of 500 x 10 mm i.d. packed with reversed-phase silica gel. As a result, nine target amides with over 95% purity, i.e., 50 mg of (2E,4E)-N-isobutyl-eicosa-2,4-dienamide, 150 mg of (2E,4E,14Z)-N-isobutyl-eicosa-2,4,14-trienamide, 110 mg of (2E,4E,12Z)-N-isobutyl-ocatadeca-2,4,12-trienamide, 50 mg of guineensine, 60 mg of pipernonaline, 75 mg of pellitorine, 63 mg of piperine, 45 mg of piperanine, and 40 mg of piperlonguminine were isolated, respectively. Structures of all compounds were identified by electrospray ionization MS, electron impact ionization MS, one- and two-dimensional NMR spectra.

Research paper thumbnail of Comparing two models of gradient elution in counter-current chromatography

Journal of Chromatography A, 2013

Gradient change of mobile phase composition is commonly used in liquid chromatography to shorten ... more Gradient change of mobile phase composition is commonly used in liquid chromatography to shorten analysis duration. Gradient elution is possible in counter-current chromatography if it is demonstrated that the mobile phase composition changes are not associated with liquid stationary phase composition changes. Also, the solute distribution ratios in initial (1) and final (2) eluting systems must be known. If the solute distribution ratios during the changing mobile phase composition are modeled, the full gradient separation can be modeled using classical equations of liquid chromatography. Another approach allowed modeling empirically the gradient step. It considered the decreasing volume of mobile phase 1 and the increasing volume of mobile phase 2 used at each gradient time to derive a very simple equation. The two equations were compared computing the retention volumes of five test solutes. A remarkable agreement was observed considering the very different mathematical expressions of the two models. The step-gradient method was also modeled and its results compared to those of the linear gradient method.

Research paper thumbnail of Comparative Study on Catalytic Performances for Low-temperature CO Oxidation of Cu–Ce–O and Cu–Co–Ce–O Catalysts

Research paper thumbnail of The preparation and catalytic behavior of copper–cerium oxide catalysts for low-temperature carbon monoxide oxidation

Applied Catalysis A: General, 2005

Research paper thumbnail of Glycine-assisted hydrothermal synthesis of peculiar porous α-Fe2O3 nanospheres with excellent gas-sensing properties

Analytica Chimica Acta, 2010

Research paper thumbnail of Modeling gradient elution in countercurrent chromatography: Efficient separation of tanshinones from Salvia miltiorrhizaBunge

Journal of Separation Science, 2012

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifu... more Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.