Dong Pei

Efficient method for the screening and identification of anti-diabetic components in the leaves of Olea europaea L.

In this article, an efficient method of high speed counter-current chromatography (HSCCC) coupled with post-column on-line evaluation was developed to screen, isolate and identify the major anti-diabetic compounds present in the leaves of Olea europaea L. The HSCCC separation employed a two-step process: first, an optimized two-phase system composed of ethyl acetate–water (1 : 1) was used to separate the extraction; then, a solvent system composed of butanol–water–acetic acid (1 : 1 : 0.1) was applied to further separate the anti-diabetic active compounds. The eluant was detected by post-column evaluation with α-amylase used in both steps. It was found that five major constituents of the O. europaea L. leaf extracts displayed potential anti-diabetic activity. Their structures were identified by 1H- and 13C-Nuclear Magnetic Resonance (NMR) as Oleuropein, Ligstroside, Hydroxytyrosol, Tyrosol and Luteolin-7-O-β-D-glucoside.

Effect of Ionic Liquids on Preparative Separation of Flavonoid Compounds in the Extract from Brassica napus L. Pollen using High-Performance Counter-Current Chromatography

To investigate the effect of ionic liquids (ILs) as additives to a two-phase solvent system using high-performance counter-current chromatography, the two structurally similar flavonoids, Kaempferol-3, 4′-di-O-β-D-glucoside and Kaempferol 3-O-β-D-(2-O-β-D-glucosyl)-glucopyranoside, were chosen as models. The effects of the length of the alkyl groups on the imidazolium ring and its counterion, and the concentrations of ILs on the K values were investigated. The results showed that the K values of the target compounds could be improved when ILs were used as additives in the two-phase solvent system. The mechanism of ILs as additives to the solvent system was discussed for the first time.

Discovery of biomarkers for oxidative stress based on cellular metabolomics

Abstract Oxidative stress has a close relationship with various pathologic physiology phenomena and the potential biomarkers of oxidative stress may provide evidence for clinical diagnosis or disease prevention. Metabolomics was employed to identify the potential biomarkers of oxidative stress. High-performance liquid chromatography–diode array detector, mass spectrometry and partial least squares discriminate analysis were used in this study. The 10, 15 and 13 metabolites were considered to discriminate the model group, vitamin E-treated group and l-glutathione-treated group, respectively. Some of them have been identified, namely, malic acid, vitamin C, reduced glutathione and tryptophan. Identification of other potential biomarkers should be conducted and their physiological significance also needs to be elaborated.

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.

Polysaccharide from Enteromorpha prolifera enhances non-specific immune responses and protection against Vibrio splendidus infection of sea cucumber

This study aimed to evaluate the effects of polysaccharide from Enteromorpha prolifera (PEP2) on the non-specific immune responses of sea cucumber. The non-specific humoral and cellular responses were determined, and sea cucumbers were challenged by Vibrio splendidus. The results indicate that PEP2 had no significant effect on the total coelomocyte counts. Both phagocytic capacity and respiratory burst activity were significantly increased by PEP2. Among the humoral responses, the activities of acid phosphatase, catalase and superoxide dismutase of sea cucumber were significantly enhanced by PEP2. However, no difference in alkaline phosphatase activity was observed between the experimental and control groups. In the challenge test, we found that PEP2 decreased the mortality rate of sea cucumbers and enhanced their resistance to V. splendidus. Thus, PEP2 could enhance the non-specific immune activity of sea cucumbers. PEP2 exhibited potent immunomodulatory properties and can be explored as a novel potential immunostimulant of sea cucumber.

Discovery and identification of potential biomarkers for alcohol-induced oxidative stress based on cellular metabolomics.

Biomarkers involved in alcohol-induced oxidative stress play an important role in alcoholic liver disease prevention and diagnosis. Alcohol-induced oxidative stress in human liver L-02 cells was used to discover the potential biomarkers. Metabolites from L-02 cells induced by alcohol were measured by high-performance liquid chromatography and mass spectrometry. Fourteen metabolites that allowed discrimination between control and model groups were discovered by multivariate statistical data analysis (i.e. principal components analysis, orthogonal partial least-squares discriminate analysis). Based on the retention time, UV spectrum and LC-MS findings of the samples and compared with the authentic standards, eight biomarkers involved in alcohol-induced oxidative stress, namely, malic acid, oxidized glutathione, γ-glutamyl-cysteinyl-glycine, adenosine triphosphate, phenylalanine, adenosine monophosphate, nitrotyrosine and tryptophan, were identified. These biomarkers offered important targets for disease diagnosis and other researches.

EFFECTIVE ON-LINE COMBINATION OF HIGH SHEAR TECHNIQUE AND CONTINUOUS SAMPLE INJECTION IN HIGH-PERFORMANCE COUNTER-CURRENT CHROMATOGRAPHY FOR ISOLATION AND PURIFICATION OF POLYPHENOLS IN GREEN TEA

A new sample preparation method of high shear dispersing emulsifier (HSDE) coupled with continuous sample injection in high-performance counter-current chromatography (HPCCC) was successfully used for the extraction and online isolation of caffeine and two polyphenolic compounds from green tea. The lower phase of hexane-ethyl acetate–methanol–water (1:8:1:8, v/v/v/v) was used as both the HSDE solvent and HPCCC mobile phase. In one time sample loading, 1.5 mg of (-)-epicatechin-3-gallate, 5.0 mg of (-)-epigallocatechin-3-gallate, and 3.1 mg of caffeine with the purity over 95.0% determined by high performance liquid chromatography (HPLC), could be obtained from about 0.1 g of raw material of green tea. Ten time sample injections were realized in HSDE extraction−HPCCC separation process, and the quantity could be magnified about decuple, 13.8 mg of (-)-epicatechin-3-gallate, 46.3 mg of (-)-epigallocatechin-3-gallate, and 28.9 mg of caffeine could obtain from 1.0 g of raw material of green tea. The compounds were analyzed by HPLC and identified by their chromatograms and their retention time compared with that of authentic reference compounds. It was the first time combining HSDE with continuous sample injection in HPCCC for effective isolation and purification of active compounds from natural products. The mechanism of HSDE extraction was illustrated.

Evaluation and Application of a Novel Quantitative Antioxidant Activity Assay Based on Cellular Metabolomics

A novel quantitative antioxidant activity assay based on cellular metabolomics, named cellular metabolomics antioxidant activity (CMAA) assay, was established and applied in this paper. CMAA assay evaluates antioxidant activity by considering the change rules of the cellular metabolites of different treatment groups of human liver carcinoma cell line HepG2 cells subjected to oxidative stress. This assay considers cellular metabolites as the main analytical index, principal components analysis (PCA), and orthogonal projections to latent structures discriminant analysis (OPLS-DA) as the main multi- and megavariate data analysis method and vitamin E (VE) as a standard substance to quantify antioxidant activities. The antioxidant activities of flavonoids extracted from Cynomorium songaricum Rupr. (CS) were measured by the CMAA assay. The results showed that the antioxidant activity of flavonoids extracted from CS was successfully evaluated using the CMAA assay, and the antioxidant activity of flavonoids extracted from CS was about 1/5 of the same concentration of VE. It indicated that the proposed approach, as an effective tool for evaluating the antioxidant capacity, was feasible.