Solid-phase adsorption methodologies of naturally occurring anthraquinones: A review

INTRODUCTION

Solid-phase extraction applied to plant matrices is nowadays a well-validated technique allowing to concentrate and purify different secondary metabolites. Several classes of phytochemicals have been selectively extracted by this methodology. During the last decade attention has been focused on biologically active anthraquinones from numerous sources like edible, healthy, and medicinal plants.

OBJECTIVES

The aim of this review is to provide a detailed literature survey of the solid-phase adsorption methodologies for the extraction of natural anthraquinones reported so far and to discuss and propose future directions in this field of research.

MATERIALS AND METHODS

Substructure search was performed in the SciFinder Scholar, PubMed, Medline, and Scopus databases.

RESULTS

The first report about application of solid-phase adsorption for the purification of anthraquinones appeared in the literature in 2002. From this date, and in particular during recent years, the most notable examples included the use of chitin- and chitosan-based polymers, of molecularly imprinted polymers, of coated magnetic nanoparticles, of miniaturized matrix solid-phase dispersion, of functionalized resins, of differently structured lamellar solids, and finally of vortex-synchronized matrix solid-phase dispersion.

CONCLUSIONS

The herein detailed solid-phase adsorption methodologies are powerful tools to selectively extract natural anthraquinones and/or provide anthraquinone-enriched phytopreparations. Nevertheless, many other important methods have been applied to synthetic anthraquinones (e.g., azo dyes). These could be conveniently employed also for natural anthranoids. Studies in this field are discussed in this review article.

Combination of UPLC-Q-TOF/MS and Network Pharmacology to Reveal the Mechanism of Qizhen Decoction in the Treatment of Colon Cancer

Traditional Chinese medicine (TCM) has been utilized for the treatment of colon cancer. Qizhen decoction (QZD), a potential compound prescription of TCM, possesses multiple biological activities. It has been proven clinically effective in the treatment of colon cancer. However, the molecular mechanism of anticolon cancer activity is still not clear. This study aimed to identify the chemical composition of QZD. Furthermore, a collaborative analysis strategy of network pharmacology and cell biology was used to further explore the critical signaling pathway of QZD anticancer activity. First, ultraperformance liquid chromatography-quadrupole time-of-flight/mass spectrometry (UPLC-Q-TOF/MS) was performed to identify the chemical composition of QZD. Then, the chemical composition database of QZD was constructed based on a systematic literature search and review of chemical constituents. Moreover, the common and indirect targets of chemical components of QZD and colon cancer were searched by multiple databases. A protein-protein interaction (PPI) network was constructed using the String database (https://www.string-db.org/). All of the targets were analyzed by Gene Oncology (GO) bioanalysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and the visual network topology diagram of "Prescription-TCM-Chemical composition-Direct target-Indirect target-Pathway" was constructed by Cytoscape software (v3.7.1). The top molecular pathway ranked by statistical significance was further verified by molecular biology methods. The results of UPLC-Q-TOF/MS showed that QZD had 111 kinds of chemical components, of which 103 were unique components and 8 were common components. Ten pivotal targets of QZD in the treatment of colon cancer were screened by the PPI network. Targets of QZD involve many biological processes, such as the signaling pathway, immune system, gene expression, and so on. QZD may interfere with biological pathways such as cell replication, oxygen-containing compounds, or organic matter by protein binding, regulation of signal receptors or enzyme binding, and affect cytoplasm and membrane-bound organelles. The main antitumor core pathways were the apoptosis metabolic pathway, the PI3K-Akt signal pathway, and so on. Expression of the PI3K-Akt signal pathway was significantly downregulated after the intervention of QZD, which was closely related to the inhibition of proliferation and migration of colon cancer cells by cell biology methods. The present work may facilitate a better understanding of the effective components, therapeutic targets, biological processes, and signaling pathways of QZD in the treatment of colon cancer and provide useful information about the utilization of QZD.

Compensate for or Minimize Matrix Effects? Strategies for Overcoming Matrix Effects in Liquid Chromatography-Mass Spectrometry Technique: A Tutorial Review

In recent decades, mass spectrometry techniques, particularly when combined with separation methods such as high-performance liquid chromatography, have become increasingly important in pharmaceutical, bio-analytical, environmental, and food science applications because they afford high selectivity and sensitivity. However, mass spectrometry has limitations due to the matrix effects (ME), which can be particularly marked in complex mixes, when the analyte co-elutes together with other molecules, altering analysis results quantitatively. This may be detrimental during method validation, negatively affecting reproducibility, linearity, selectivity, accuracy, and sensitivity. Starting from literature and own experience, this review intends to provide a simple guideline for selecting the best operative conditions to overcome matrix effects in LC-MS techniques, to obtain the best result in the shortest time. The proposed methodology can be of benefit in different sectors, such as pharmaceutical, bio-analytical, environmental, and food sciences. Depending on the required sensitivity, analysts may minimize or compensate for ME. When sensitivity is crucial, analysis must try to minimize ME by adjusting MS parameters, chromatographic conditions, or optimizing clean-up. On the contrary, to compensate for ME analysts should have recourse to calibration approaches depending on the availability of blank matrix. When blank matrices are available, calibration can occur through isotope labeled internal standards and matrix matched calibration standards; conversely, when blank matrices are not available, calibration can be performed through isotope labeled internal standards, background subtraction, or surrogate matrices. In any case, an adjusting of MS parameters, chromatographic conditions, or a clean-up are necessary.

Analysis of the chemical components of Qixianqingming granules and their metabolites in rats by UPLC-ESI-Q-TOF-MS

Qixianqingming granules (QXQM) comprise a traditional Chinese medicine (TCM) formula that was developed based on the combination of TCM theory and clinical practice. This formula has been proven to effectively treat asthma. In this study, an analytical procedure using ultraperformance liquid chromatography, coupled with electrospray ionization quadrupole time-of-flight mass spectrometry, was established for the rapid separation and sensitive identification of the chemical components in QXQM and its metabolites in serum of rats. Seventy-two compounds were systematically identified in QXQM, including flavonoids, terpenoids, anthraquinones, phenylethanoid glycosides, stilbenes, alkaloids, and organic acids. Thirteen prototype compounds and 29 metabolites were detected in the serum of rats. The results provided fundamental information for further studying the mechanisms and clinical application of QXQM.

Preparation of two-dimensional magnetic molecularly imprinted polymers based on boron nitride and a deep eutectic solvent for the selective recognition of flavonoids

Two-dimensional (2D) boron nitride (BN) were developed as a 2D scaffold material in preparation of magnetic molecularly imprinted polymers (MMIPs).

A label-free electrochemical aptasensor based on magnetic biocomposites with Pb2+-dependent DNAzyme for the detection of thrombin

Herein, a novel magnetic biocomposite (Fe₃O₄@Au-S1/S2) was applied to analyze thrombin. The Fe₃O₄@Au-S1/S2 consisted of Fe₃O₄@Au nanoparticles (Fe₃O₄@Au NPs) as carriers for magnetic separation and magnetic field-induced self-assembly, thiolated complementary strand (S1) anchored based on Au-S bond and thrombin binding aptamer (S2) as a recognition element. As a redox indicator, methylene blue (MB) can be adsorbed to DNA anchored on the surface of Fe₃O₄@Au NPs by electro-static interaction. In the absence of thrombin, MB were adsorbed on double-stranded DNA (S1/S2) which anchored on Fe₃O₄@Au NPs and a high electrochemical signal of MB was recorded by Differential pulse voltammetry. Conversely, the complementary strand (S1) exposed after thrombin competitively bonded with aptamer. The introduction of Pb²⁺-dependent DNAzyme (S3) split S1 at specific rA site, resulting in the significantly decreased adsorption capacity of MB. Thus, the thrombin detection could be recorded by monitoring the electrochemical signal reduction of MB through incubation of thrombin with S3. This method exhibited a high sensitivity toward thrombin with a broad linear range from 5 pmol L^-1 to 5 nmol L^-1 and a limit of detection of 1.8 pmol L^-1.

Application of novel ternary deep eutectic solvents as a functional monomer in molecularly imprinted polymers for purification of levofloxacin

A series of ecofriendly ternary deep eutectic solvents (DESs) with different molar ratios were prepared as candidate functional monomers. Three of the optimal ternary DESs as functional monomers were applied to the preparation of molecularly imprinted polymers (MIPs). After synthesis, the proposed polymers were characterized by elemental analysis (EA), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller surface area measurements (BET) and Fourier transform infrared spectroscopy (FT-IR). These MIPs based on ternary DESs with different molar ratios exhibited different absorption capacities of levofloxacin. A sample of levofloxacin (500ng) was dissolved in a millet extractive (10mL). All MIPs were used as SPE adsorbents to purify the extracts. According to characterization result, the ternary DES-3 (1:3:1.5) was joined in the synthetic process of MIP-1. The green ternary DES-3-based MIPs had the best selectivity recovery for levofloxacin (91.4%) from the millet extractive. The best selectivity of MIP-1 was attributed to the novel monomer (ternary DES) in the preparation of the materials. Overall, ternary DES-based MIPs have potential applications as media in many research areas.

Identification and characterization of fluvastatin metabolites in rats by UHPLC/Q-TOF/MS/MS and in silico toxicological screening of the metabolites

The present study reports the in vivo and in vitro identification and characterization of metabolites of fluvastatin, the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor, using liquid chromatography-mass spectrometry (LC-MS). In vitro studies were conducted by incubating the drug with human liver microsomes and rat liver microsomes. In vivo studies were carried out by administration of the drug in the form of suspension to the Sprague-Dawley rats followed by collection of urine, faeces and blood at different time points up to 24 h. Further, samples were prepared by optimized sample preparation method, which includes freeze liquid extraction, protein precipitation and solid phase extraction. The extracted and concentrated samples were analysed using ultrahigh-performance liquid chromatography-quadruple time-of-flight tandem mass spectrometry. A total of 15 metabolites were observed in urine, which includes hydroxyl, sulphated, desisopropyl, dehydrogenated, dehydroxylated and glucuronide metabolites. A few of the metabolites were also present in faeces and plasma samples. In in vitro studies, a few metabolites were observed that were also present in in vivo samples. All the metabolites were characterized using ultrahigh-performance liquid chromatography-quadruple time-of-flight tandem mass spectrometry in combination with accurate mass measurement. Finally, in silico toxicity studies indicated that some of the metabolites show or possess carcinogenicity and skin sensitization. Several metabolites that were identified in rats are proposed to have toxicological significance on the basis of in silico evaluation. However, these metabolites are of no human relevance. Copyright © 2017 John Wiley & Sons, Ltd.

Purification of antibiotics from the millet extract using hybrid molecularly imprinted polymers based on deep eutectic solvents

Deep eutectic solvents (DESs) are potential ecofriendly surfactants for the preparation of molecularly imprinted polymers (MIPs).

A novel adduct of ECG fused to piceid and four new dimeric stilbene glycosides from Polygonum cuspidatum

Polyflavanostilbene B (1), an unusual adduct of epicatechin-3-O-gallate fused to piceid through a carbon–carbon bond, four new dimeric stilbene glycosides (2–5), and four new compounds (6–9), were isolated from the rhizome of Polygonum cuspidatum.

Development of hydrophilic magnetic molecularly imprinted polymers by directly coating onto Fe3O4 with a water-miscible functional monomer and application in a solid-phase extraction procedure for iridoid glycosides

Development of hydrophilic magnetic molecularly imprinted polymers by directly coating onto Fe₃O₄ with a water-miscible functional monomer and application in a solid-phase extraction procedure for iridoid glycosides.