On-line two-dimensional countercurrent chromatography×high performance liquid chromatography system with a novel fragmentary dilution and turbulent mixing interface for preparation of coumarins from Cnidium monnieri

Retention correlation and orthogonality between reversed phase countercurrent chromatography and liquid chromatography based on solvent strength

Correlation of elution performance between reversed phase countercurrent chromatography and liquid chromatography was investigated using five selected natural components. Theoretical guidance for orthogonality of two-dimensional countercurrent chromatography and liquid chromatography was proposed. The difference in retention behavior between countercurrent chromatography and liquid chromatography was studied when the mobile phase was composed of methanol and water by measuring the partition behavior of five selected compounds in two typical biphasic solvent systems composed of n-hexane-ethyl acetate-methanol-water and chloroform-methanol-water. An orthogonal diagram between countercurrent chromatography and liquid chromatography was obtained by normalized treatment of the measured partition coefficients and capacity factors. The experimental results showed that each biphasic solvent system used for countercurrent chromatography had a high orthogonality with liquid chromatography when a specific volume ratio was used.

Multi-dimensional preparation of Thymus quinquecostatus Celak. by normal-phase flash chromatography coupled to counter-current chromatography

In this study, a multi-dimensional chromatography system was developed by integrating normal-phase flash chromatography and counter-current chromatography to isolate flavonoids, phenylpropanoids, and thymol from the aerial parts of Thymus quinquecostatus Celak. In the online multi-dimensional switching system, a normal-phase flash chromatograph packed with 1.2 g of dry homogeneous silica gel mixture (containing 600 mg of methanol extract) was connected to counter-current chromatography via a six-port valve. Two two-dimensional separations were performed using n-heptane-ethyl acetate-methanol-water (6:4:6:4, v/v) and ethyl acetate-water solvent systems sequentially to separate the constituents of Thymus quinquecostatus Celak. The upper phase of the former solvent system was utilized as both elution solvent for flash chromatography and the stationary phase for counter-current chromatography, while the lower phase of the latter solvent system containing 10 mM trifluoroacetic acid was employed as elution solvent for flash chromatography and one mobile phase in pH gradient counter-current chromatography. Thymol (7) and xanthomicrol (8), two hydrophobic ingredients, were purified in the initial two-dimensional separation. The subsequent two-dimensional separation yielded six hydrophilic compounds, namely dihydrokaempferol-7-O-D-glucopyranoside (1), lithospermic acid (2), luteolin-7-O-glucuronide (3), rosmarinic acid (4), messerschmidin (5) and apigenin-7-O-D-glucuronide (6). This study represents the first documented use of online multi-dimensional normal-phase flash chromatography coupled to counter-current chromatography for separating constituents from Thymus quinquecostatus Celak.

Efficient Separation of the Methoxyfuranocoumarins Peucedanin, 8-Methoxypeucedanin, and Bergapten by Centrifugal Partition Chromatography (CPC)

Pure methoxyfuranocoumarins were isolated from a crude petroleum ether extract (CPE; Soxleth extraction efficiency 12.28%) from fruits of Peucedanum tauricum MB. (Apiaceae) by counter-current chromatography in a hydrostatic equilibrium system (centrifugal partition chromatography-CPC). The optimized biphasic solvent system composed of n-heptane-ethyl acetate-methanol-water (5:2:5:2; v/v/v/v) in the ascending mode of elution was used (3 mL/min, 1600 rpm). In the single run, peucedanin (P), 8-methoxypeucedanin (8MP), and bergapten (5MOP) were obtained as pure as 95.6%, 98.1%, and c.a. 100%, respectively. The carefully optimized and developed CPC was effectively transferred from the analytical to the semi-preparative scale (where 20 mg and 150 mg of CPE were loaded, respectively). Identification and quantitative analysis of methoxyfuranocoumarins was carried out in the plant material, in the CPE, and in individual CPC fractions by use of validated high-performance liquid chromatography with diode array detection and mass spectrometry (HPLC-DAD-ESI-MS). For the separation steps, the extraction/isolation recovery was calculated. In this case, CPC proved to be an effective tool for the simultaneous isolation and separation of P, 8MP, and 5MOP from a multicomponent plant matrix, without additional pre-purification steps. The high purity of the obtained plant metabolites makes it possible to consider their use in pharmacological or biological studies.

Fruit extracts to control pathogenic Escherichia coli: A sweet solution

Escherichia coli is a major cause of diarrhea and is as well responsible for extraintestinal infections in humans and animals. Many pathotypes have been defined for this ubiquitous microorganism on the basis of the virulence attributes. For the last 70 years, antibiotics have been used to control infections caused by E. coli. However, with the resistance observed with many strains these drugs are less recommended. Plant extracts, in particular fruit, represent a source of bioactive compounds that could be beneficial in the control of infectious diseases caused by E. coli. These could have bacteriostatic or bactericidal potential or could be used as synergic agents to amplify the activity of antibiotics for which the germs present some level of resistance. Certain studies also revealed that fruit extracts could act directly on virulence characters to attenuate the pathogenic capacity of microorganisms. This review intent to expose the scant but rapidly growing information available that shows that fruit, used as crude extracts or purified molecules, should be considered to manage diverse types of infections caused by E. coli.

Development of an on-line mixed-mode gel liquid chromatography×reversed phase liquid chromatography method for separation of water extract from Flos Carthami

A novel on-line comprehensive two-dimensional liquid chromatography (2D-LC) method by coupling mixed-mode gel liquid chromatography (MMG-LC) with reversed phase liquid chromatography (RPLC) was developed. A mixture of 17 reference compounds was used to study the separation mechanism. A crude water extract of Flos Carthami was applied to evaluate the performance of the novel 2D-LC system. In the first dimension, the extract was eluted with a gradient of water/methanol over a cross-linked dextran gel Sephadex LH-20 column. Meanwhile, the advantages of size exclusion, reversed phase partition and adsorption separation mechanism were exploited before further on-line reversed phase purification on the second dimension. This novel on-line mixed-mode Sephadex LH-20×RPLC method provided higher peak resolution, sample processing ability (2.5mg) and better orthogonality (72.9%) versus RPLC×RPLC and hydrophilic interaction liquid chromatography (HILIC)×RPLC. To the best of our knowledge, this is the first report of a mixed-mode Sephadex LH-20×RPLC separation method with successful applications in on-line mode, which might be beneficial for harvesting targets from complicated medicinal plants.

Comprehensive two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography for analysis of toad skin

An analytical two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography (2D NPLC × RPLC) system was constructed with a newly developed thermal evaporation assisted adsorption (TEAA) interface. This novel TEAA interface with heating temperature above solvent boiling point allowed fast removal of organic NPLC solvent and successfully solved the solvent incompatibility problem between NPLC and RPLC. The system achieved rapid on-line solvent exchange between the two dimensions within a short modulation time of 190 s and was applied in the analysis of an extract from the skin of Bufo bufo gargarizans. This is the first time to realize the on-line comprehensive analysis of a moderate polar natural product by coupling NPLC with reversed phase ultra-high performance liquid chromatography (UHPLC). To be highlighted, with the TEAA interface, the 2D NPLC × RPLC system provided excellent resolution and orthogonality (75.2%), when compared with that of 2D RPLC × RPLC.

Development of small-volume, microfluidic chaotic mixers for future application in two-dimensional liquid chromatography

We report a microfluidic chaotic micromixer with staggered herringbone grooves having a geometry optimized for fast mobile-phase modification at the interface of a two-dimensional liquid chromatography system.

Potential of the Cnidium monnieri fruits as an immune enhancer in Escherichia coli infection model

OBJECTIVES

The Cnidium monnieri fruits (CMF) were studied how they act on immune system as a novel immunostimulator against the infectious disease.

METHODS

Macrophages were treated with CMF, and nitric oxide (NO) and tumour necrosis factor-α (TNF-α) were measured, and phagocytosis of macrophages was detected using FITC-labelled Escherichia coli. The protective effect of CMF against E. coli infection in mice was examined. The survival rate was monitored daily for up to 5 days. And then the viable bacteria count of serum and the immunological mediator (NO, TNF-α, interleukin (IL)-12 and IL-6) of serum, splenocyte and peritoneal macrophages were analysed.

KEY FINDINGS

The CMF significantly enhanced the concentrations of NO and TNF-α and the phagocytosis activity in macrophages. The oral administration of CMF for five consecutive days before infection prolonged the survival rate. Treatment with CMF significantly stimulated the phagocytosis of peritoneal macrophages and induced the immunological mediator of serum, splenocyte and peritoneal macrophages against the E. coli infection.

CONCLUSIONS

The host-protective effects of CMF might be archived by improving immune response, and CMF could act to prevent pathogenic microbial infections with immunomodulation.

New on-line separation workflow of microbial metabolites via hyphenation of analytical and preparative comprehensive two-dimensional liquid chromatography

Microbial metabolites represent an important source of bioactive natural products, but always exhibit diverse of chemical structures or complicated chemical composition with low active ingredients content. Traditional separation methods rely mainly on off-line combination of open-column chromatography and preparative high performance liquid chromatography (HPLC). However, the multi-step and prolonged separation procedure might lead to exposure to oxygen and structural transformation of metabolites. In the present work, a new two-dimensional separation workflow for fast isolation and analysis of microbial metabolites from Chaetomium globosum SNSHI-5, a cytotoxic fungus derived from extreme environment. The advantage of this analytical comprehensive two-dimensional liquid chromatography (2D-LC) lies on its ability to analyze the composition of the metabolites, and to optimize the separation conditions for the preparative 2D-LC. Furthermore, gram scale preparative 2D-LC separation of the crude fungus extract could be performed on a medium-pressure liquid chromatograph×preparative high-performance liquid chromatography system, under the optimized condition. Interestingly, 12 cytochalasan derivatives, including two new compounds named cytoglobosin Ab (3) and isochaetoglobosin Db (8), were successfully obtained with high purity in a short period of time. The structures of the isolated metabolites were comprehensively characterized by HR ESI-MS and NMR. To be highlighted, this is the first report on the combination of analytical and preparative 2D-LC for the separation of microbial metabolites. The new workflow exhibited apparent advantages in separation efficiency and sample treatment capacity compared with conventional methods.

High quantum yield and pH sensitive fluorescence dyes based on coumarin derivatives: fluorescence characteristics and theoretical study

The fluorescence coumarin derivatives were synthesized by an efficient one-pot, three-component reaction in 80–90% yields.