Xin-Yi Huang

Simultaneous determination of three diarylheptanoids and an α-tetralone derivative in the green walnut husks (Juglans regia L.) by high-performance liquid chromatography with photodiode array detector

By optimizing extraction, separation and analytical conditions, a reliable and accurate high-performance liquid chromatographic (HPLC) method coupled with photodiode array detector (DAD) at room temperature is developed for simultaneous determination of three diarylheptanoids (juglanin A, juglanin B, rhoiptelol) and an alpha-tetralone derivative (regiolone) in methanol extracts from the green walnut husks (Juglans regia L.) The sample pretreatment process involved the reflux extraction using methanol as the extract with a ratio of liquor to sample of 15 mL/g. The separation was achieved on a SinoChrom ODS-AP C(18) column with gradient elution using acetonitrile and 2% (v/v) acetic acid in water. The intra-day and inter-day precision (RSD%) for the analytes ranged from 1.08 to 1.51 and 0.60 to 1.13, respectively. The average recoveries obtained were from 88.4% to 96.2% for the analytes with RSDs below 3.13%. The correlation coefficients of the calibration curve exceeded 0.999. The detection limits were 0.51, 0.25, 0.32 and 0.35 ng at a signal-to-noise ratio of 3, respectively. Quantitative analyses of the samples from different grown sites and in obtained different months showed that the contents of the analytes varied significantly. The method was then successfully applied for the detection and isolation of a new diarylheptanoid derivative in the green walnut husks (J. regia L.). The structure of the new compound was elucidated by various spectroscopic methods including 2D NMR techniques (COSY, HMQC, HMBC), HR-ESI-MS and X-ray single-crystal diffraction analysis.

A review on chiral separation by counter-current chromatography: Development, applications and future outlook

Chiral separation has been a remarkably active area of research over the past long time and it still stays that way. Over the last few decades, counter-current chromatography (CCC) was successfully applied to the field of chiral separation. It provides an attractive approach to obtain pure enantiomer, particularly in preparative application because of its unique advantages of high load capacity, low solvent consumption and easy scale-up. The last several years great strides have been made in chiral separation by CCC, ranging from novel elution modes such as recycling elution mode and multiple dual mode elution to more specialized approaches such as pH-zone-refining and biphasic chiral recognition technologies. These developments have greatly improved the resolution of enantiomers and promoted the application of CCC in the field of chiral separation. Although not as popular as its application to the field of separation of natural product, the development of chiral separation by CCC should not be underrated. In this review article, we refer to the development, applications and future outlook of chiral separation by CCC, with emphasis on topics of its history, mechanism, advantages, limitations, current development and challenges. Meanwhile, its orientation of continued evolution and future outlook also have been discussed. While some scientific and technological problems have not yet been solved thoroughly, chiral separation by CCC has demonstrated potential advantages and prospects in this field and has good chance at preparative enantioseparation.

Spiral counter‐current chromatography: Design, development, application, and challenges

Depending on the rapid growth in the radial gradient of the centrifugal force, spiral counter-current chromatography can greatly improve the retention of stationary phase, especially for the aqueous two-phase systems with ultra-polar and high viscosity that are not well retained in the conventional multilayer coils counter-current chromatography. As a result, it is an attractive and alternative technology that is suited for separation of hydrophilic compounds and has led to many exciting progress in recent years. This review presents the recent advances and applications of spiral counter-current chromatography, including its major benefits and limitations, some novel methods to improve the separation efficiency and its applications in separation of real samples. In addition, the remaining challenges and future perspectives on development of spiral counter-current chromatography also are proposed in this article.

DPPH-HPLC-DAD analysis combined HSCCC for screening and identification of radical scavengers in Cynomorium songaricum Rupr.

A combinative method using the 2,2-diphenyl-1-picrylhydrazyl (DPPH)-high performance liquid chromatography (HPLC)-diode array detector (DAD) and high-speed counter-current chromatography (HSCCC) has been developed to screen and separate radical scavengers from the water extract of Cynomorium songaricum Rupr. Under the target guidance of the DPPH-HPLC-DAD experiment, 3 compounds were found to possess potential antioxidant activities. In order to identify the chemical structures of those compounds, the HSCCC method with a two-phase solvent system composed of ethyl acetate–water (1 : 1; v/v) was developed to isolate and purify the active compounds. Three compounds, 14.3 ± 0.7 mg of (+)-catechin (1), 15.2 ± 0.6 mg of (−)-epicatechin (2) and 11.3 ± 0.4 mg oleuropein (3) were obtained from 600 mg of crude sample with purities of 97.8%, 98.3% and 95.6%, respectively, as determined by HPLC. Their structures were elucidated by electrospray ionization-mass spectrometry (ESI-MS), 1H nuclear magnetic resonance (NMR) and 13C NMR. Among them, oleuropein was obtained from C. songaricum for the first time. The peak order of the three compounds in the HSCCC chromatogram was completely different from that in the HPLC chromatogram. Even both HSCCC and HPLC methods that are employed in this paper were in reversed phase mode. The elution order of HSCCC was determined by the hydrophobicity of the compounds, while the elution order of HPLC may be affected by some other interactions between the stationary phase and the compounds such as hydrogen bonding and steric effects. In addition, antioxidant activities of the three compounds were evaluated by the methods of DPPH radical scavenging assay. All of them showed high radical scavenging activities with the EC50 values being 16.97 ± 0.02, 11.15 ± 0.09 and 41.32 ± 0.20 μg mL−1 for (+)-catechin, (−)-epicatechin and oleuropein, respectively.

Surface modification of polytetrafluoroethylene column for two-stationary phase separations by counter-current chromatography.

To improve the separation capability of CCC, a novel solid-liquid two-stationary phases CCC (ASP-CCC) column was prepared employing graphene oxide (GO) conjugated poly-dopamine (PD) coating (GO/PD) as auxiliary stationary phase (ASP). The results of Scanning electron microscopy (SEM), contact angle and X-ray photoelectron spectroscopy (XPS) indicated that nanostructured GO and PD were successfully grafted on the inner wall of the PTFE column. Three alkaloid compounds were selected as the target analytes to evaluate the performance of the novel column. Because of the intermolecular force (hydrogen bond, electrostatic interaction and π-π interaction) between the ASP and model compounds, three analytes were well separated with this novel ASP-CCC column. Additionally, the novel column exhibited higher stationary phase retention ratio, about 8%, than original column without changing the chromatographic condition. Furthermore, the eluotropic sequence of analytes on novel column was in accordance with that in the original column. This suggested that the novel column is a CCC column with auxiliary stationary phase (ASP) in its own right, and the present separation mode is the combination of partition chromatography and adsorption chromatography.

Advances in Technology of Countercurrent Chromatography for Separation of Protein and Peptide

Abstract Countercurrent chromatography is a kind of continuous and effective liquid-liquid partition chromatography with many unique characteristics such as large load capacity, no irreversible adsorption, high recovery rate, low risk of sample denaturation and so on, which has irreplaceable advantages in the separation of proteins and peptides. This review presents the advances of several kinds of new technology of countercurrent chromatography in the separation of proteins and peptides. The development prospect of this field is also discussed.

Determination of a novel diarylheptanoid (Juglanin B) from green walnut husks (Juglans regia L.) in rat plasma by high-performance liquid chromatography.

A simple and reliable analytical method based on high-performance liquid chromatography (HPLC) coupled with a diode array detector (DAD) was developed for the determination of a novel diarylheptanoid (Juglanin B) from green walnut husks (Juglans regia L.) in rat plasma using rhoiptelol as an internal standard. Chromatographic separation was carried out on a Sinochrom ODS-AP C(18) column (250 x 4.6 microm i.d., 5 mm) with acetonitrile-10 mM postassium dihydrogen phosphate (pH = 3; 55:45, v/v) as mobile phase, and the detection wavelength was set at 214 nm. The plasma samples were prepared using methanol as protein precipitator. The extraction recovery of Juglanin B ranged from 70.26 to 78.59%, and the calibration curve had a good linearity in the range 0.08-50 microg/mL (r(2) = 0.9932). The RSDs of intra- and inter-day precision ranged from 1.19 to 4.92% and 4.35 to 4.54%, respectively. The HPLC-DAD method described is a simple, rapid and reliable method for the determination of Juglanin B level and for use in studies involving pharmacokinetics.

A simple gradient equilibrium method for better separation in countercurrent chromatography

The stationary phase retention is one of the most important parameters in countercurrent chromatography. In this work, a simple gradient equilibrium method was developed to further improve the stationary phase retention based on the optimized condition in the traditional equilibrium model. Meanwhile, this novel gradient equilibrium method was used to separate three flavone model compounds and compared with the conventional isocratic equilibrium method to evaluate the separation efficiency. The results show that better resolution or shorter separation time could be achieved with gradient equilibrium compared to isocratic equilibrium. So this novel equilibrium method has enormous potential for obtaining a better separation or saving the separating time in the preparative separation of target compounds.

Development of overlapping repeated separation of steviol glycosides with counter current chromatography and a comparison with a conventional repeated separation method

Repeated separation is a valuable method in counter current chromatography, especially on a preparative scale. It can greatly reduce the separation time and the consumption of solvent. In this study, an overlapping repeated separation method was developed. Meanwhile, this method was used to separate steviol glycosides and compared with conventional repeated separation method. The results show that both methods are effective ways for countercurrent chromatography to prepare compounds but the overlapping repeated separation method requires fewer time and solvent than the conventional repeated separation method. So this novel repeated separation method has enormous potential for a preparative separation of target compounds and is very useful for the high-throughput purification of natural products.

Variable selection and chemometric models for discriminating symptomatic gout based on a metabolic target analysis: Discriminating Symptomatic Gout Based On Metabolic Target Analysis

In clinical practice, uric acid is frequently used as a diagnostic criterion in gout. However, gout is commonly confused with other diseases, including rheumatoid arthritis, soft tissue joint injury, and hyperuricosuric calcium oxalate urolithiasis. Two new strategies—graphical index of separation and subwindow permutation analysis—were applied to understand the metabolic changes induced by gout. Metabolic target analysis was performed using high performance liquid chromatography with a diode array detector. Compared with the nongout samples, the concentrations of uric acid, uracil, inosine, adenosine, and tryptophan are different in gout samples, and these metabolites could be used as important diagnostic markers. However, the uric acid, uracil, phenylalanine, tryptophan, and adenine concentrations differed between acute and chronic gout. We confirmed the metabolic disorder of uracil during the basic development of gout. In the gout and nongout groups, the recognition rate of the model reached 0.98, whereas the value of recognition ability was only 0.79 when uric acid was used as a single variable. In the acute and chronic class of gout, the recognition rate of the model was 0.90 and that of uric acid was only 0.62. Variable selection combined with chemometric models can be used as a supplementary method for the diagnosis and prognosis of gout in clinical practice.