Recent advances in bio-affinity chromatography for screening bioactive compounds from natural products

A strategy for inhibitors screening of xanthine oxidase based on colorimetric sensor combined with affinity chromatography technology

The discovery of enzyme inhibitors from natural products is a crucial aspect in the development of therapeutic drugs. However, the complexity of natural products presents a challenge in developing simple and efficient methods for inhibitor screening. Herein, we have developed an integrated analytical model for screening xanthine oxidase (XOD) inhibitors that combines simplicity, accuracy, and efficiency. This model utilizes a colorimetric sensor and affinity chromatography technology with immobilized XOD. The colorimetric sensor procedure can quickly identify whether there are active components in complex samples. Subsequently, the active components in the samples identified by the colorimetric sensor procedure were further captured, separated, and identified through affinity chromatography. The integrated analytical model can significantly enhance the efficiency and accuracy of inhibitor screening. The proposed method was applied to screen for an activity inhibitor of XOD in five natural medicines. As a result, a potential active ingredient for XOD, polydatin, was successfully identified from Polygoni Cuspidati Rhizoma et Radix. This work is anticipated to offer new insights for the screening of enzyme inhibitors from natural medicines.

Immobilized cells on microcarriers for efficient and biomimetic screening of active compounds acting on FGFR4 from Fructus evodiae

Cell membrane coating strategies have been increasingly researched in new drug discovery from complex herb extracts. However, these systems failed to maintain the functionality of the coated cells because cell membranes, not whole cells were used. Original source cells can be used as a vector for active compound screening in a manner that mimics in vivo processes. In this study, we established a novel approach to fabricate high-density fibroblast growth factor receptor 4 (FGFR4)-HEK293 cells on microcarriers covered with collagen through cell culture and covalent immobilization between proteins. This method enables the efficient screening of active compounds from herbs. Two compounds, evodiamine and limonin, were obtained from Fructus evodiae, which were proven to inhibit the FGFR4 target. Enhanced immobilization effects and negligible damage to FGFR4-HEK293 cells treated with paraformaldehyde were successfully confirmed by immunofluorescence assays and transmission electron microscopy. A column was prepared and used to analyze different compounds. The results showed that the method was selective, specific, and reproducible. Overall, the high density of cells immobilized on microcarriers achieved through cell culture and covalent immobilization represents a promising strategy for affinity screening. This approach highlights the potential of the affinity screening method to identify active compounds from an herbal matrix against designed targets and its prospects for use in drug discovery from herbs.

Recent advances in bioaffinity strategies for preclinical and clinical drug discovery: Screening natural products, small molecules and antibodies

Bioaffinity drug screening strategies have gained popularity in preclinical and clinical drug discovery for natural products, small molecules and antibodies owing to their superior selectivity, the large number of compounds to be screened and their ability to minimize the time and expenses of the drug discovery process. This paper provides a systematic summary of the principles of commonly used bioaffinity-based screening methods, elaborates on the success of bioaffinity in clinical drug development and summarizes the active compounds, preclinical drugs and marketed drugs obtained through affinity screening methods. Owing to the high demand for new drugs, bioaffinity-guided screening techniques will play a greater part in clinical drug development.

Novel 3D-Printed Microfluidic Magnetic Platform for Rapid DNA Isolation

This study presents a novel miniaturized device as a 3D-printed microfluidic magnetic platform specifically designed to manipulate magnetic microparticles in a microfluidic chip for rapid deoxyribonucleic acid (DNA) isolation. The novel design enables the movement of the magnetic particles in the same or opposite directions with the flow or suspends them in continuous flow. A computational model was developed to assess the effectiveness of the magnetic manipulation of the particles. Superparamagnetic monodisperse silica particles synthesized in-house are utilized for the isolation of fish sperm DNA and human placenta DNA. It was demonstrated that the proposed platform can perform DNA isolation within 10 min with an isolation efficiency of 50% at optimum operating conditions.

A green, efficient and stable platform based on hyperbranched quaternized hydrothermal magnetic chitosan nanospheres integrated cytomembranes for screening drug candidates from natural products

Compared with traditional tedious organic solvent-assisted separation process in natural medicinal chemistry, cytomembrane (CM) fishing technique became a more appealing and greener choice for screening bioactive components from natural products. However, its large-scale practical value was greatly weakened by the easy fall-off of CMs from magnetic supports, rooted in the instability of common Fe3O4 particles and their insufficient interaction with CMs. In this research, a new green biostable platform was developed for drug screening through the integration of hyperbranched quaternized hydrothermal magnetic carbon spheres (HQ-HMCSs) and CMs. The positive-charged HQ-HMCSs were constructed by chitosan-based hydrothermal carbonization onto Fe3O4 nanospheres and subsequent aqueous hyperbranching quaternization with 1,4-butanediol diglycidyl ether and methylamine. The strong interaction between HQ-HMCSs and CMs was formed via electrostatic attraction of HQ-HMCSs to negative-charged CMs and covalent linkage derived from the epoxy-amine addition reactions. The chemically stable HMCSs and its integration with CMs contributed to dramatically higher stability and recyclability of bionic nanocomposites. With the fishing of osteoblast CMs integrated HQ-HMCSs, two novel potential anti-osteoporosis compounds, narcissoside and beta-ionone, were discovered from Hippophae rhamnoides L. Enhanced osteoblast proliferation, alkaline phosphatase, and mineralization levels proved their positive osteogenesis effects. Preliminary pharmacological investigation demonstrated their potential action on membrane proteins of estrogen receptor alpha and insulin-like growth factor 1. Furthermore, beta-ionone showed apparent therapeutic effects on osteogenic lesions in zebrafish. These results provide a green, stable, cost-efficient, and reliable access to rapid discovery of drug leads, which verifiably benefits the design of nanocarbon-based biocomposites with increasingly advanced functionality.

Review on NMR as a tool to analyse natural products extract directly: Molecular structure elucidation and biological activity analysis

INTRODUCTION

Natural products, the small organic molecules produced by plants, microbes and invertebrates, often present in the form of a mixture, this leads to the structural characterisation of natural extracts often requiring time-consuming multistep purification procedures. Nuclear magnetic resonance (NMR) technology is traditionally utilised as a tool for the structural elucidation of pure compounds. Contemporarily, an up-to-date trend in the application of NMR in natural product research is shifting to the direct NMR analysis of crude mixtures, to obtain molecular structure and biological activity information without performing cumbersome separation.

OBJECTIVE

To review works of literature on the evolution, principle and progress of NMR technologies for analysing mixtures, we focus on the successful application of NMR technologies in direct analysis of natural product extracts.

METHODOLOGY

Based on our research experience, academic tracking and extensive literature search, which involved, but not limited to, the use of various databases, like Web of Knowledge and PubMed. The keywords used, in various combinations, to retrieve recent literature on the successful application of NMR technologies to sheer natural product extracts, and excluded artificially natural product mixture and biofluid.

RESULTS

NMR technologies for direct natural extracts analysis, including two-dimensional J-resolved spectroscopy (2D-JRES), pure shift NMR, diffusion-ordered NMR spectroscopy (DOSY), statistical correlation spectroscopy (STOCSY), concentration-ordered NMR spectroscopy (CORDY), saturation transfer difference (STD) and water-ligand observed via gradient spectroscopy (WaterLOGSY) were illustrated.

CONCLUSIONS

By these methods, molecular structure and biological activity information will be directly obtained from NMR analysis of natural products extract, aiming to save experimental time and expenses.

Deep eutectic solvent extraction combined with magnetic bead ligand fishing for identification of α-glucosidase inhibitors from Pueraria lobata

In this study, a deep eutectic solvent (DES) extraction combined with a magnetic bead ligand affinity analytical method was developed and used for α-glucosidase inhibitor identification from Pueraria lobata. Several critical parameters affecting the analysis performance, including the type of DES, molar ratio, water amount, pH, salt concentration, and volume of DES, were investigated. The selected analytical sample preparation conditions were as follows. The composition of DES is choline chloride-1,4-butanediol (1:3), the water content is 40%, pH is 7.0 and the volume of extraction solution is 2 mL. The obtained sample extraction solution was analyzed directly using α-glucosidase immobilized magnetic beads (GMBs). Three α-glucosidase inhibitors in Pueraria lobata, including puerarin, daidzin, and daidzein, were identified. Luteolin was used as a positive control to evaluate the method's selectivity. Results showed it could selectively bond to the GMBs in the DES. As the affinity analysis was performed directly in a DES, the solution-removing process could be avoided. The intra-day and inter-day precisions of the method are 5.21% and 6.38%, respectively. The solvent amount was 1/50-1/2000 of that used in traditional methods.

Identifying the active ingredients of carbonized Typhae Pollen by spectrum-effect relationship combined with MBPLS, PLS, and SVM algorithms

Typhae Pollen (TP) and its carbonized product (carbonized Typhae Pollen, CTP), as cut-and-dried herbal drugs, have been widely used in the form of slices in clinical settings. However, the two drugs exhibit a great difference in terms of their clinical efficacy, for TP boasts an effect of removing blood stasis and promoting blood circulation, while CTP typically presents a hemostatic function. Since the active ingredients of CTP, so far, still remain unclear, this study aimed at identifying the active ingredients of CTP by spectrum-effect relationship approach coupled with multi-block partial least squares (MBPLS), partial least squares (PLS), and support vector machine (SVM) algorithms. In this study, the chemical profiles of a series of CTP samples which were stir-fried for different duration (denoted as CTP0∼CTP9) were firstly characterized by UHPLC-QE-Orbitrap MS. Then the hemostatic effect of the CTP samples was evaluated from the perspective of multiple parameters-APTT, PT, TT, FIB, TXB2, 6-keto-PGF1α, PAI-1 and t-PA-using established rat models with functional uterine bleeding. Subsequently, MBPLS, PLS and SVM were combined to perform spectrum-effect relationship analysis to identify the active ingredients of CTP, followed by an in vitro hemostatic bioactivity test for verification. As a result, a total of 77 chemical ingredients were preliminarily identified from the CTP samples, and the variations occurred in these ingredients were also analyzed during the carbonizing process. The study revealed that all the CTP samples, to a varying degree, showed a hemostatic effect, among which CTP6 and CTP7 were superior to the others in terms of the hemostatic effect. The block importance in the projection (BIP) indexes of MBPLS model indicated that flavonoids and organic acids made more contributions to the hemostatic effect of CTP in comparison to other ingredients. Consequently, 9 bioactive ingredients, including quercetin-3-O-glucoside, kaempferol-3-O-rutinoside, quercetin, kaempferol, isorhamnetin, 2-methylenebutanedioic acid, pentanedioic acid, benzoic acid and 3-hydroxybenzoic acid, were further identified as the potential active ingredients based on PLS and SVM models as well as the in vitro verification. This study successfully revealed the bioactive ingredients of CTP associated with its hemostatic effect, and also provided a scientific basis for further understanding the mechanism of TP processing. In addition, it proposed a novel path to identify the active ingredients for Chinese herbal medicines.

Immobilization of M3 Muscarinic Receptor to Rapidly Analyze Drug-Protein Interactions and Bioactive Components in a Natural Plant

Despite its increasing application in pursing potential ligands, the capacity of receptor affinity chromatography is greatly challenged as most current research studies lack a comprehensive characterization of the ligand-receptor interaction, particularly when simultaneously determining their binding thermodynamics and kinetics. This work developed an immobilized M3 muscarinic receptor (M3R) affinity column by fixing M3R on amino polystyrene microspheres via the interaction of a 6-chlorohexanoic acid linker with haloalkane dehalogenase. The efficiency of the immobilized M3R was tested by characterizing the binding thermodynamics and kinetics of three known drugs to immobilized M3R using a frontal analysis and the peak profiling method, as well as by analyzing the bioactive compounds in Daturae Flos (DF) extract. The data showed that the immobilized M3R demonstrated good specificity, stability, and competence for analyzing drug-protein interactions. The association constants of (-)-scopolamine hydrochloride, atropine sulfate, and pilocarpine to M3R were determined to be (2.39 ± 0.03) × 10⁴, (3.71 ± 0.03) × 10⁴, and (2.73 ± 0.04) × 10⁴ M^-1, respectively, with dissociation rate constants of 27.47 ± 0.65, 14.28 ± 0.17, and 10.70 ± 0.35 min^-1, respectively. Hyoscyamine and scopolamine were verified as the bioactive compounds that bind to M3R in the DF extract. Our results suggest that the immobilized M3R method was capable of determining drug-protein binding parameters and probing specific ligands in a natural plant, thus enhancing the effectiveness of receptor affinity chromatography in diverse stages of drug discovery.

Advances in receptor chromatography for drug discovery and drug-receptor interaction studies

Receptor chromatography involves high-throughput separation and accurate drug screening based on specific drug-receptor recognition and affinity, which has been widely used to screen active compounds in complex samples. This review summarizes the immobilization methods for receptors from three aspects: random covalent immobilization methods, site-specific covalent immobilization methods and dual-target receptor chromatography. Meanwhile, it focuses on its applications from three angles: screening active compounds in natural products, in natural-product-derived DNA-encoded compound libraries and drug-receptor interactions. This review provides new insights for the design and application of receptor chromatography, high-throughput and accurate drug screening, drug-receptor interactions and more. Teaser: This review summarizes the immobilization methods of receptors and the application of receptor chromatography, which will provide new insights for the design and application of receptor chromatography, rapid drug screening, drug-receptor interactions and more.

Screening of trypsin inhibitors in Cotinus coggygria Scop. extract using at-line nanofractionation coupled with semi-preparative reverse-phase liquid chromatography

In this study, an at-line nanofractionation (ANF) platform was successfully fabricated in parallel with mass spectrometry and trypsin inhibitory bioactivity assessment for rapid screening of trypsin inhibitors (TIs) from natural products for the first time. After systematic optimization, the ANF platform was applied to screen and identify TIs in the extract of a traditional Chinese herb, i.e., Cotinus coggygria Scop. The semi-preparative reverse-phase liquid chromatography was used subsequently to further simplify and enrich the insufficiently separated components. After comprehensive evaluation and validation, the ANF platform successfully identified 12 compounds as potential TIs, including 8 flavonoids and 2 organic acids. Additionally, a comparison study was conducted using two other ligand fishing approaches, i.e., capillary monolithic and magnetic beads-based trypsin-immobilized enzyme microreactors, which successfully identified 8 identical flavonoids as TIs. Importantly, the molecular docking study showed the molecular interactions between enzymes and inhibitors, thus strongly supporting the experimental results. Overall, this work has fully demonstrated the feasibility of the established ANF platform for screening TIs from Cotinus coggygria Scop., and proved its great prospects for screening bioactive components from natural products.

Two-dimensional chromatography in screening of bioactive components from natural products

INTRODUCTION

Screening and analysis of bioactive components from natural products is a fundamental part of new drug development and innovation. Two-dimensional (2D) chromatography has been demonstrated to be an effective method for screening and preparation of specific bioactive components from complex natural products.

OBJECTIVE

To collect details of application of 2D chromatography in screening of natural product bioactive components and to outline the research progress of different separation mechanisms and strategies.

METHODOLOGY

Three screening strategies based on 2D chromatography are reviewed, including traditional separation-based screening, bioactivity-guided screening and affinity chromatography-based screening. Meanwhile, in order to cover these aspects, selections of different separation mechanisms and modes are also presented.

RESULTS

Compared with traditional one-dimensional (1D) chromatography, 2D chromatography has unique advantages in terms of peak capacity and resolution, and it is more effective for screening and identifying bioactive components of complex natural products.

CONCLUSION

Screening of natural bioactive components using 2D chromatography helps separation and analysis of complex samples with greater targeting and relevance, which is very important for development of innovative drug leads.

Ten Years Milestones in Xanthine Oxidase Inhibitors Discovery: Febuxostat-Based Inhibitors Trends, Bifunctional Derivatives, and Automatized Screening Assays

Xanthine oxidase (XO) is an enzyme involved in the oxidative process of hypoxanthine and xanthine to uric acid (UA). This process also produces reactive oxygen species (ROS) as byproducts. Both UA and ROS are dangerous for human health, and some health conditions trigger upregulation of XO activity, which results in many diseases (cancer, atherosclerosis, hepatitis, gout, and others) given the worsened scenario of ROS and UA overproduction. So, XO became an attractive target to produce and discover novel selective drugs based on febuxostat, the most recent XO inhibitor out of only two approved by FDA. Under this context, high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) have been successfully applied to rapidly and easily screen for bioactive compounds, isolated or in complex natural matrixes, that act as enzyme inhibitors through the use of an immobilized enzyme reactor (IMER). This article’s goal is to present advances comprising febuxostat-based XO inhibitors as a new trend, bifunctional moieties capable of inhibiting XO and modulating ROS activity, and in-flow techniques employing an IMER in HPLC and CE to screen for synthetic and natural compounds that act as XO inhibitors.

Efficient screening of pancreatic lipase inhibitors from cod meat hydrolysate through ligand fishing strategy

Obesity has become an increasingly serious public health problem. Pancreatic lipase (PL) is identified as a ideal target for the prevention and treatment of obesity. Orlistat, the only approved PL inhibitor (PLI), is a powerful weight loss drug but has many side effects. Therefore, there is an urgent need to discover powerful PLIs with high safety. Protein hydrolysate has been demonstrated to be a treasure trove of PLIs, but recognizing responsible functional peptides from them is like looking for a needle in a haystack. In this work, we synthesized and optimized a PL ligand fishing model (PLLFM) using magnetic nanoparticles (MNPs), then PLLFM was used to quickly fish out potential PLIs from the Cod meat hydrolysate (CMH). Finally, two new PLIs, GSPPPSG and KLEGDLK were identified with IC₅₀ of 0.60 and 1.08 mg/mL, respectively. The Lineweaver-Burk diagram showed that GSPPPSG is a non-competitively dominant mixed-type PLI, whereas KLEGDLK is a competitive inhibitory-type PLI. Moreover, molecular docking suggested that both peptides can stably bind to the key amino acid residues of the PL active site, mainly through hydrogen bonding, hydrophobic, and electrostatic interactions. In general, we not only established a method to rapidly fish out potential PLIs from protein hydrolysate, but also provided safe and efficient lead compounds for the development of novel diet foods or drugs.

Rapid profiling of potential antitumor polymethoxylated flavonoids in natural products by integrating cell biospecific extraction with neutral loss/diagnostic ion filtering-based high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry

INTRODUCTION

Citri Reticulatae Pericarpium Viride (CRPV, Qing Pi in Chinese) has been widely used in traditional Chinese medicine. Polymethoxylated flavonoids (PMFs), which are a special group of flavonoids with strong antitumor activity, are broadly distributed in citrus peels. However, systematic investigation of antitumor PMFs in CRPV has received little attention to date.

OBJECTIVES

An MCF-7 cell biospecific extraction method integrated with neutral loss/diagnostic ion filtering-based HPLC-QTOF-MS/MS strategy was developed for rapid and specific profiling of antitumor PMFs and systematic identification of PMFs in CRPV.

METHODOLOGY

By incubating MCF-7 cells with CRPV extract, potential antitumor PMFs specifically bound to cells and were isolated. Then, by systematic investigation of fragmentation pathways, neutral loss and diagnostic ion filtering strategies were proposed to comprehensively and accurately identify PMFs.

RESULTS

Sixteen antitumor PMFs were unambiguously or tentatively identified. Among them, minor compound 15 (5-hydroxy-6,7,8,3',4'-pentamethoxyflavone with a free hydroxyl group at C-5) exhibited excellent antitumor activity, with an IC₅₀ value of 2.81 ± 0.76 μg/mL, which is lower than that of 5-fluorouracil (IC₅₀ , 4.92 ± 0.83 μg/mL). Nobiletin (12) and tangeretin (16), two major PMFs, presented moderate antitumor activities with IC₅₀ values of 13.06 ± 1.85 and 17.07 ± 1.18 μg/mL, respectively, and their contents were sensitively and precisely determined.

CONCLUSIONS

To the best of our knowledge, this is the first report on the systematic investigation of antitumor PMFs in CRPV. The study will lay a foundation for the quality control and clinical application of CRPV.

Fisetin Inhibits Trypsin Activity and Suppresses the Growth of Colorectal Cancer in Vitro and in Vivo

Colorectal cancer (CRC) is a malignant tumor with high incidence and bad prognosis. Therapies, which are more safe and effective, are urgently needed. Trypsin is proved to be crucial to cancer proliferation and migration, therefore, it is possible to control cancers by modulating its activity. Fisetin is a flavone with trypsin inhibition properties that was screened from more than 45 compounds derived from traditional Chinese medicine (TCM). However, the effects and mechanisms of fisetin on CRC have not been well investigated. In this study, we evaluated the effects of fisetin on 2 different CRC cell lines. Fisetin remarkably inhibited CRC cell proliferation and migration, as well as induced cell apoptosis and Go/G1 phase arrest in a dose-dependent manner. Mechanistic studies revealed that these effects were mediated partially through signaling pathways involving cell cycle regulators p21, p27, cyclinD1, and NF kappa B (NF-κB) p65. Administration of fisetin also significantly suppressed the tumor growth in tumor-bearing NOD/Shi-scid-IL2R gamma (null) (NOG) mice that had been inoculated with human HCT116 cells. Fisetin at the given dosage did not induce significant acute or chronic toxicity in rats. These data provide a potential therapeutic strategy for CRC.

Chemical characterization and DPP-IV inhibitory activity evaluation of tripeptides from Gynura divaricata (L.) DC

ETHNOPHARMACOLOGICAL RELEVANCE

Gynura divaricata (L.) DC. (GD), a herbal medicine, has been used for the prevention and treatment of hyperglycemia in China. However, hypoglycemic ingredients within GD have not yet been well studied.

AIM OF THE STUDY

The aim of this study was to explore undiscovered compounds with dipeptidyl peptidase IV (DPP-IV) inhibitory activity within GD.

MATERIALS AND METHODS

A four-step strategy was developed to explore undiscovered DPP-IV inhibitors within GD. First, the components were preliminarily characterized using UHPLC-HRMS combined with a library search. Second, preliminarily characterized compounds were searched for potential bioactivity. Third, a mixture of these preliminarily characterized compounds was isolated and thoroughly characterized based on fragmentation patterns associated with molecular networking. Fourth, the activities of these compounds were verified using DPP-IV inhibitory assay and molecular docking.

RESULTS

Diprotin A, a tripeptide inhibitor against DPP-IV, was identified. Thereafter, a mixture of twenty-five diprotin A analogs was isolated and characterized, which exhibited IC₅₀ of 0.40 mg/mL for DPP-IV. Molecular docking results also confirmed the interactions between the tripeptide analogs and DPP-IV mainly via H-bonds and hydrophobic interactions.

CONCLUSIONS

This is the first report of DPP-IV inhibitors within GD. These findings demonstrate that the extract of GD might be beneficial for the treatment of type 2 diabetes mellitus, and is expected to promote further development and utilization of GD in herbal medicine.

Targeting and Covalently Immobilizing the EGFR through SNAP-Tag Technology for Screening Drug Leads

Membrane protein immobilization is particularly significant in in vitro drug screening and determining drug-receptor interactions. However, there are still some problems in the immobilization of membrane proteins with controllable direction and high conformational stability, activity, and specificity. Cell membrane chromatography (CMC) retains the complete biological structure of membrane proteins. However, conventional CMC has the limitation of poor stability, which results in its limited life span and low reproducibility. To overcome this limitation, we propose a method for the specific covalent immobilization of membrane proteins in cell membranes. We used the SNAP-tag as an immobilization tag fused to the epidermal growth factor receptor (EGFR), and Cys145 located at the active site of the SNAP-tag reacted with the benzyl group of O⁶-benzylguanine (BG). The SNAP-tagged EGFR was expressed in HEK293 cells. We captured the SNAP-tagged EGFR from the cell membrane suspension onto a BG-derivative-modified silica gel. Our immobilization strategy improved the life span and specificity of CMC and minimized loss of activity and nonspecific attachment of proteins. Next, a SNAP-tagged EGFR/CMC online HPLC-IT-TOF-MS system was established to screen EGFR antagonists from Epimedii folium. Icariin, magnoflorine, epimedin B, and epimedin C were retained in this model, and pharmacological assays revealed that magnoflorine could inhibit cancer cell growth by targeting the EGFR. This EGFR immobilization method may open up possibilities for the immobilization of other membrane proteins and has the potential to serve as a useful platform for screening receptor-binding leads from natural medicinal herbs.

Rapid Screening for EGFR Inhibitor in Rhei Radix et Rhizoma by HTRF Assay Coupled with HPLC Peak Fractionation

In this paper, an HPLC peak fractionation approach combined with homogeneous time-resolved fluorescence analysis is proposed for screening epidermal growth factor receptor inhibitors from Rhei Radix et Rhizoma. With this approach, the amount of sample used for a single HPLC run is sufficient for performing a multiple assay due to the miniaturization ability of the homogeneous time-resolved fluorescence technology. This allows for improving the stability and repeatability of the activity assay for each fraction. From a total of 26 fractions collected from the Rhei Radix et Rhizoma extract, 13 fractions exhibit inhibitory activity against the epidermal growth factor receptor. The structures of activity compounds were determined by HPLC-LTQ-Orbitrap MS, revealing the presence of gallic acid, rhein, and emodin with IC₅₀ values of 21.5, 5.29, and 10.2 µM, respectively. The ligand epidermal growth factor receptor interactions were explored by molecular docking simulations, and the inhibitory effects of the three compounds on A549 cell growth were tested in vitro by an MTT assay. This study demonstrates the suitability of the present screening method for drug discovery in natural products.

Affinity chromatography: A review of trends and developments over the past 50 years

The field of affinity chromatography, which employs a biologically-related agent as the stationary phase, has seen significant growth since the modern era of this method began in 1968. This review examines the major developments and trends that have occurred in this technique over the past five decades. The basic principles and history of this area are first discussed. This is followed by an overview of the various supports, immobilization strategies, and types of binding agents that have been used in this field. The general types of applications and fields of use that have appeared for affinity chromatography are also considered. A survey of the literature is used to identify major trends in these topics and important areas of use for affinity chromatography in the separation, analysis, or characterization of chemicals and biochemicals.

Recent advances in screening active components from natural products based on bioaffinity techniques

Natural products have provided numerous lead compounds for drug discovery. However, the traditional analytical methods cannot detect most of these active components, especially at their usual low concentrations, from complex natural products. Herein, we reviewed the recent technological advances (2015–2019) related to the separation and screening bioactive components from natural resources, especially the emerging screening methods based on the bioaffinity techniques, including biological chromatography, affinity electrophoresis, affinity mass spectroscopy, and the latest magnetic and optical methods. These screening methods are uniquely advanced compared to other traditional methods, and they can fish out the active components from complex natural products because of the affinity between target and components, without tedious separation works. Therefore, these new tools can reduce the time and cost of the drug discovery process and accelerate the development of more effective and better-targeted therapeutic agents.

Monitoring of phosphorylation using immobilized kinases by on-line enzyme bioreactors hyphenated with High-Resolution Mass Spectrometry

Nucleosides analogues are the cornerstone of the treatment of several human diseases. They are especially at the forefront of antiviral therapy. Their therapeutic efficiency depends on their capacity to be converted to the active nucleoside triphosphate form through successive phosphorylation steps catalyzed by nucleoside/nucleotide kinases. In this context, it is mandatory to develop a rapid, reliable and sensitive enzyme activity test to evaluate their metabolic pathways. In this study, we report a proof of concept to directly monitor on-line nucleotide multiple phosphorylation. The methodology was developed by on-line enzyme bioreactors hyphenated with High-Resolution Mass Spectrometry detection. Human Thymidylate Kinase (hTMPK) and human Nucleoside Diphosphate Kinase (hNDPK) were covalently immobilized on functionalized silica beads, and packed into micro-bioreactors (40 μL). By continuous infusion of substrate into the bioreactors, the conversion of thymidine monophosphate (dTMP) into its di- (dTDP) and tri-phosphorylated (dTTP) forms was visualized by monitoring their Extracted Ion Chromatogram (EIC) of their [M - H]^- ions. Both bioreactors were found to be robust and durable over 60 days (storage at 4 °C in ammonium acetate buffer), after 20 uses and more than 750 min of reaction, making them suitable for routine analysis. Each on-line conversion step was shown rapid (<5 min), efficient (conversion efficiency > 55%), precise and repeatable (CV < 3% for run-to-run analysis). The feasibility of the on-line multi-step conversion from dTMP to dTTP was also proved. In the context of selective antiviral therapy, this proof of concept was then applied to the monitoring of specificity of conversion of two synthesized Acyclic Nucleosides Phosphonates (ANPs), regarding human Thymidylate Kinase (hTMPK) and vaccina virus Thymidylate Kinase (vvTMPK).

Recent applications of immobilized biomaterials in herbal analysis

Immobilization of biomaterials developed rapidly due to the great promise in improving their stability, activity and even selectivity. In this review, the immobilization strategies of biomaterials, including physical adsorption, encapsulation, covalent attachment, cross-linking and affinity linkage, were briefly introduced. Then, the major emphasis was focused on the reported various types of immobilized biomaterials, including proteins, enzymes, cell membrane and artificial membrane, living cells, carbohydrates and bacteria, used in the herbal analysis for bioactive compound screening, drug-target interaction evaluation and chiral separation. In addition, a series of carrier materials applied in biomaterials immobilization, such as magnetic nanoparticles, metal-organic frameworks, silica capillary column, cellulose filter paper, cell membrane chromatography, immobilized artificial membrane chromatography and hollow fiber, were also discussed. Perspectives on further applications of immobilized biomaterials in herbal analysis were finally presented.