Ligand fishing of anti-neurodegenerative components from Lonicera japonica using magnetic nanoparticles immobilised with monoamine oxidase B

Phenolamides from Rootstocks of Lycium ruthenicum Murr by Ligand Fishing and Their Neuroprotective Effects

Lycium ruthenicum Murr is an important edible and medicinal plant widely cultivated in Northwest China. Our previous study found that its fruit possessed rich polyphenols exhibiting significant neuroprotective effects, inspiring us to investigate the active constituents of its rootstocks, which have never been reported. In this study, we rapidly identified four phenolamides (1-4) possessing monoamine oxidase B (MAO-B) inhibitory effect by using MAO-B-functionalized cellulose filter paper-based ligand fishing, and their structures were elucidated with NMR and MS. Compounds 1, 2, and 4 exhibited moderate inhibitory effect on MAO-B with IC50 values of 71.44 ± 1.81, 28.97 ± 1.20, and 25.58 ± 0.74 μM, respectively, and enzyme kinetic analysis, molecular docking, and molecular dynamics further revealed the inhibition mechanism. All four phenolamides displayed a neuroprotective effect against 1-methyl-4-phenylpyridinium -induced SH-SY5Y cells model, among which 2 and 4 significantly reduced intracellular MAO-B activity and improved the ATP content. Western blot revealed that compounds 2 and 4 alleviated the oxidative stress through up-regulation of the expression of Nrf2 and HO-1 protein, promoting mitophagy via activating the PINK1/Parkin pathway. Moreover, compounds 2 and 4 extended the lifespan, dopamine and ATP levels, locomotor behavior, and olfactory ability of the PINK1B9 flies, a drosophila model of Parkinson's disease. Meanwhile, compounds 1-4 showed potent antioxidative activities on DPPH, ABTS+, and PTIO radical scavenging assays. These results revealed the health-promoting effects of the rootstocks in preventing and treating neurodegenerative diseases, laying the scientific foundation for the exploitation of this plant byproduct for the development of functional food formulations and pharmaceutical products.

Screening bioactive compounds from Qianghuo (Notopterygium incisum) volatile oil via COX-2 magnetic ligand fishing

Qianghuo (the rhizomes and radixes of Notopterygium incisum Ting ex H.T. chang) is a traditional Chinese medicine, and widely used as an anti-inflammatory, anodyne, antifebrile agent. Qianghuo volatile oil also exhibits the same properties, and the effects are probably related to the inhibition of cyclooxygenase (COX), but its bioactive components are not clear yet. To figure out the bioactive components of Qianghuo volatile oil target to cyclooxygenase-2 (COX-2), a ligand fishing method using immobilized COX-2 magnetic beads (COX-2-MBS) and gas chromatography-mass spectrometry (GC-MS) were developed to identify the compounds that act on COX-2. Nine ligands, including 3-carene, β-caryophyllene, eucalyptol, α-terpinene, Limonene, δ-terpinene, α-pinene, β-pinene and γ-terpinene, were specifically captured by COX-2-MBS. Among them, 3-carene, β-caryophyllene, and eucalyptol in Qianghuo volatile oil were isolated and confirmed by in vitro inhibition and in vivo anti-inflammatory activity assays as selective inhibitor against COX-2. The IC50 values were 13.5, 10.1, and 7.6 μM, respectively. Compared with the model, 3-carene, β-caryophyllene, and eucalyptol considerably reduced ear swelling and paw edema. Moreover, 3-carene and eucalyptol significantly decreased the changes of COX-2 expression in RAW264.7 cells activated by LPS. Our study validated that the developed ligand-fishing method using COX-2-MBs coupled with GC-MS can be applied to recognize COX-2 inhibitors in Qianghuo volatile oil. In vitro/vivo assay showed 3-carene and eucalyptol in Qianghuo volatile oil had strong inhibition against COX-2. This study may provide novel methods for discovering active components for volatile oil-based drug development or aromatherapy.

Monoamine oxidase and neurodegeneration: Mechanisms, inhibitors and natural compounds for therapeutic intervention

Mammalian flavoenzyme Monoamine oxidase (MAO) resides on the outer mitochondrial membrane (OMM) and it is involved in the metabolism of different monoamine neurotransmitters in brain. During MAO mediated oxidative deamination of relevant substrates, H2O2 is released as a catalytic by-product, thus serving as a major source of reactive oxygen species (ROS). Under normal conditions, MAO mediated ROS is reported to propel the functioning of mitochondrial electron transport chain and phasic dopamine release. However, due to its localization onto mitochondria, sudden elevation in its enzymatic activity could directly impact the form and function of the organelle. For instance, in the case of Parkinson's disease (PD) patients who are on l-dopa therapy, the enzyme could be a concurrent source of extensive ROS production in the presence of uncontrolled substrate (dopamine) availability, thus further impacting the health of surviving neurons. It is worth mentioning that the expression of the enzyme in different brain compartments increases with age. Moreover, the involvement of MAO in the progression of neurological disorders such as PD, Alzheimer's disease and depression has been extensively studied in recent times. Although the usage of available synthetic MAO inhibitors has been instrumental in managing these conditions, the associated complications have raised significant concerns lately. Natural products have served as a major source of lead molecules in modern-day drug discovery; however, there is still no FDA-approved MAO inhibitor which is derived from natural sources. In this review, we have provided a comprehensive overview of MAO and how the enzyme system is involved in the pathogenesis of different age-associated neuropathologic conditions. We further discussed the applications and drawbacks of the long-term usage of presently available synthetic MAO inhibitors. Additionally, we have highlighted the prospect and worth of natural product derived molecules in addressing MAO associated complications.

Screening of monoamine oxidase B inhibitors in Tibetan strawberry by ligand fishing based on enzyme functionalized cellulose filter paper

Tibetan strawberry (Fragaria nubicola) is a wild medicinal and edible plant in Tibet possessing various health benefits such as neuroprotection and anti-oxidation. However, there has been little study reported on its chemical constituents. To investigate the inhibitors of monoamine oxidase B (MAO-B) in Tibetan strawberry, we immobilized the enzyme onto cellulose filter paper for the first time to develop a new screening method. Two known glycosides (compounds 1 and 2) and one new iridoid glucoside (Compound 3) were fished out by this method, which was found to effectively inhibit MAO-B with IC50 values of 16.95 ± 0.93, 24.69 ± 0.20, and 46.77 ± 0.78 μM, respectively. Molecular docking and kinetic analysis were performed to reveal the inhibition mechanism of these compounds. Furthermore, compound 1 exhibited neuroprotective effects against 6-OHDA-induced injury on PC12 cells. The developed method exhibits the advantages of rapidness and effectiveness in screening of MAO-B inhibitors from complex herbal extracts.

Rapid Screening of Chemical Components in Salvia miltiorrhiza with the Potential to Inhibit Skin Inflammation

Hyaluronidase possesses the capacity to degrade high-molecular-weight hyaluronic acid into smaller fragments, subsequently initiating a cascade of inflammatory responses and activating dendritic cells. In cases of bacterial infections, substantial quantities of HAase are generated, potentially leading to severe conditions such as cellulitis. Inhibiting hyaluronidase activity may offer anti-inflammatory benefits. Salvia miltiorrhiza Bunge, a traditional Chinese medicine, has anti-inflammatory properties. However, its effects on skin inflammation are not well understood. This study screened and evaluated the active components of S. miltiorrhiza that inhibit skin inflammation, using ligand fishing, enzyme activity assays, drug combination analysis, and molecular docking. By combining magnetic nanomaterials with hyaluronidase functional groups, we immobilized hyaluronidase on magnetic nanomaterials for the first time in the literature. We then utilized an immobilized enzyme to specifically adsorb the ligand; two ligands were identified as salvianolic acid B and rosmarinic acid by HPLC analysis after desorption of the dangling ligands, to complete the rapid screening of potential anti-inflammatory active ingredients in S. miltiorrhiza roots. The median-effect equation and combination index results indicated that their synergistic inhibition of hyaluronidase at a fixed 3:2 ratio was enhanced with increasing concentrations. Kinetic studies revealed that they acted as mixed-type inhibitors of hyaluronidase. Salvianolic acid B had Ki and Kis values of 0.22 and 0.96 μM, respectively, while rosmarinic acid had values of 0.54 and 4.60 μM. Molecular docking revealed that salvianolic acid B had a higher affinity for hyaluronidase than rosmarinic acid. In addition, we observed that a 3:2 combination of SAB and RA significantly decreased the secretion of TNF-α, IL-1, and IL-6 inflammatory cytokines in UVB-irradiated HaCaT cells. These findings identify salvianolic acid B and rosmarinic acid as key components with the potential to inhibit skin inflammation, as found in S. miltiorrhiza. This research is significant for developing skin inflammation treatments. It demonstrates the effectiveness and broad applicability of the magnetic nanoparticle-based ligand fishing approach for screening enzyme inhibitors derived from herbal extracts.

Antidepressant effects of 70% ethanolic extract of Lonicerae japonicae flos and it contained chlorogenic acid via upregulation of BDNF-TrkB pathway in the hippocampus of mice

Lonicera japonica flos (LJF) is a common clinical herb with outstanding medicinal and nutritional value. This study aimed to evaluate the antidepressant effects of LJF's active extract and compound chlorogenic acid (CGA) around brain-derived neurotrophic factor(BDNF)-tropomyosin receptor kinase B (TrkB) pathway. The results showed that LJF's extracts and CGA had significant antidepressant effects, and the antidepressant effects of different extracts of LJF were highly positively correlated with the content of CGA (forced swimming test, r = 0.998; tail suspension test, r = 0.934). Moreover, LJF-70% ethanolic extract and CGA improved chronic unpredictable mild stress-induced depressive behavior, upregulated protein expression levels of BDNF and p-TrkB in the hippocampus, restored the damage of hippocampal neurons, and protected liver from damage. In summary, this study demonstrated for the first time that LJF-70% ethanolic extract was the active extract of LJF in antidepressant and CGA was its active compound, and the antidepressant mechanisms mainly involved the upregulation of BDNF-TrkB signaling pathway in the hippocampus of mice.

Polyphenolic glycosides with unusual four-membered ring possessing anti-Parkinson's disease potential from black wolfberry

This work reports the isolation of seven undescribed polyphenolic glycosides (1-7) together with fourteen known compounds (8-21) from the fruit of Lycium ruthenicum Murray. The structures of the undescribed compounds were identified based on comprehensive spectroscopic methods including IR, HRESIMS, NMR and ECD, and chemical hydrolysis. Compounds 1-3 possess an unusual four-membered ring, while 11-15 were firstly isolated from this fruit. Interestingly, compounds 1-3 inhibited monoamine oxidase B with IC₅₀ of 25.36 ± 0.44, 35.36 ± 0.54, and 25.12 ± 1.59 μM, respectively, and showed significant neuroprotective effect on PC12 cells injured by 6-OHDA. Moreover, compound 1 improved the lifespan, dopamine level, climbing behaviour, and olfactory ability of the PINK1^B9 flies, a Drosophila model of Parkinson's disease. This work presents the first in vivo neuroprotective evidence of the small molecular compounds in L. ruthenicum Murray fruit, indicating its good potential as neuroprotectant.

Isochlorogenic acid A alleviates dextran sulfate sodium-induced ulcerative colitis in mice through STAT3/NF-кB pathway

Isochlorogenic acid A (ICGA-A) is a dicaffeoylquinic acid widely found in various medicinal plants or vegetables, such as Lonicerae japonicae Flos and chicory, and multiple properties of ICGA-A have been reported. However, the therapeutic effect of ICGA-A on colitis is not clear, and thus were investigated in our present study, as well as the underlying mechanisms. Here we found that ICGA-A alleviated clinical symptoms of dextran sodium sulfate (DSS) induced colitis model mice, including disease activity index (DAI) and histological damage. In addition, DSS-induced inflammation was significantly attenuated in mice given ICGA-A supplementation. ICGA-A reduced the fraction of neutrophils in peripheral blood and the infiltration of neutrophils and macrophages in colon tissue, and reduced pro-inflammatory cytokine production and tight junctions in mouse models. Furthermore, ICGA-A down-regulated expression of STAT3 and up-regulated the protein level of IκBα. Our in vitro studies confirmed that ICGA-A inhibited the mRNA expression of pro-inflammatory cytokines. ICGA-A blocked the phosphorylation of STAT3, p65, and IκBα, suppressed the expression STAT3 and p65. In addition, the present study also demonstrated that ICGA-A had no obvious toxicity on normal cells and organs. Taken together, we conclude that ICGA-A mitigates experimental ulcerative colitis (UC) at least in part by inhibiting the STAT3/NF-кB signaling pathways. Hence, ICGA-A may be a promising and effective drug for treating UC.

Screening of Monoamine Oxidase Inhibitors from Seeds of Nigella glandulifera Freyn et Sint. by Ligand Fishing and Their Neuroprotective Activity

Nigella glandulifera is a traditional medicinal plant used to treat seizures, insomnia, and mental disorders among the Tibetan and Xinjiang people of China. Recent pharmacological research indicates that the seeds of this plant have a neuroprotective effect; however, the chemical components responsible for this effect are unknown. Monoamine oxidase B (MAO-B) has been recognized as a target for developing anti-Parkinson's disease drugs. In this work, MAO-B functionalized magnetic nanoparticles were used to enrich the enzyme's ligands in extracts of N. glandulifera seeds for rapid screening of MAO-B inhibitors coupled with HPLC-MS. Tauroside E and thymoquinone were found to inhibit the enzyme with IC₅₀ values of 35.85 μM and 25.54 μM, respectively. Both compounds exhibited neuroprotective effects on 6-OHDA-induced PC-12 cells by increasing the cell viability to 52% and 58%, respectively, compared to 50% of the injured cells. Finally, molecular docking indicated strong interactions of both inhibitors with the enzyme. This work shows that MAO-B functionalized magnetic nanoparticles are effective for rapid screening of anti-PD inhibitors from complex herbal mixtures and, at the same time, shows the promising potential of this plant's seeds in developing anti-PD drugs.

Screening of Monoamine Oxidase B Inhibitors from Fragaria nubicola by Ligand Fishing and Their Neuroprotective Effects

Fragaria nubicola, known as Tibetan strawberry, is an edible plant possessing various health-promoting effects. However, its functional compositions were rarely studied. In this work, monoamine oxidase B (MAO-B) inhibitors in this plant were rapidly screened using the enzyme-functionalized magnetic nanoparticles coupled with UPLC-QTOF-MS. Two inhibitors, quercetin-3-O-β-d-glucuronide-6″-methyl ester (1) and kaempferol-3-O-β-d-glucuronide-6″-methyl ester (2), were identified from this plant with the IC₅₀ values of 19.44 ± 1.17 and 22.63 ± 1.78 μM, respectively. Enzyme kinetic analysis and molecular docking were carried out to investigate the mechanism of inhibition. Contents of both compounds as well as those of total phenolics and flavonoids were quantified to be 24.76 ± 1.26, 35.59 ± 1.17, 837.67 ± 10.62, and 593.46 ± 10.37 μg/g, respectively. In addition, both compounds exhibited significant neuroprotective effects on 6-hydroxydopamine-induced PC12 cells. This is the first report on the neuroprotective components of F. nubicola, suggesting its potential for developing neuroprotective functional food.

Ligand fishing of monoamine oxidase B inhibitors from Platycodon grandiflorus (Jacq.) A.DC. roots by the enzyme functionalised magnetic nanoparticles

INTRODUCTION

As a famous traditional Chinese medicine, roots of Platycodon grandiflorus (Jacq.) A.DC. have shown multiple effects against neurodegenerative diseases. To investigate the components against Parkinson's disease (PD), the roots of P. grandiflora were selected as the research subject.

OBJECTIVE

Screening and identifying of monoamine oxidase B (MAO-B) inhibitors from the roots of P. grandiflorum via enzyme functionalised magnetic nanoparticles (MNPs)-based ligand fishing combined with high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis.

METHOD

MAO-B functionalised MNPs have been synthesised for screening MAO-B inhibitors from the roots of P. grandiflorum. The ligands were identified by HPLC-MS and nuclear magnetic resonance (NMR) analysis, and their anti-PD activity was evaluated via MAO-B inhibition assay and cell viability assay in vitro.

RESULTS

Two MAO-B inhibitors were fished out and identified by HPLC-MS as protocatechuic aldehyde (1) and coumarin (2), with the half maximal inhibitory concentrations of 28.54 ± 0.39 and 25.39 ± 0.29 μM, respectively. Among them, 1 could also significantly increase the viability of 6-hydroxydopamine-damaged PC12 cells.

CONCLUSION

The results are helpful to elucidate the anti-PD activity of the plant, and the ligand fishing method has shown good potential in discovery of MAO-B inhibitors.

Tyrosinase covalently immobilized on carboxyl functionalized magnetic nanoparticles for fishing of the enzyme's ligands from Prunellae Spica

In this study, tyrosinase was immobilized on carboxyl functionalized silica-coated magnetic nanoparticles for the first time to be used for fishing of tyrosinase's ligands present in complex plant extract. The immobilized tyrosinase was characterized by transmission electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy, thermo-gravimetric analyzer, and atomic force microscopy. The reusability and thermostability of the immobilized tyrosinase were found significantly superior to its free counterpart. Two tyrosinase's ligands, that is, caffeic acid (1) and rosmarinic acid (2), were fished out from extract of the traditional Chinese medicine Prunellae Spica by the immobilized tyrosinase. Compound 1 was found to be an activator of the enzyme with the half maximal effective concentration value of 0.27 ± 0.06 mM, while compound 2 was an inhibitor with the half maximal inhibitory concentration value of 0.14 ± 0.03 mM. Taking advantage of the convenience of magnetic separation and specific extraction ability of ligand fishing, the proposed method exhibited great potential for screening of bioactive compounds from complex matrices.

Polyphenolic Glycosides from the Fruits Extract of Lycium ruthenicum Murr and Their Monoamine Oxidase B Inhibitory and Neuroprotective Activities

The fruits ofLycium ruthenicum Murr have long been consumed as health food and used in folk medicine in China. Apart from the well-known polysaccharides, the active small molecular constituents in this fruit have not been fully studied. In this work, a systematic phytochemical study was carried out to investigate the small molecules and their potential health benefits. Nine new polyphenolic glycosides, lyciumserin A-I (1-9), together with 16 known compounds (10-25), were isolated and elucidated by high-resolution electrospray ionization mass spectrometry and comprehensive NMR analyses in combination with chemical hydrolysis. Compounds 1, 2, and 16 exhibited moderate inhibitory activity of monoamine oxidase B (MAO-B), while compounds 1 (50 μM) and 2 (100 μM) displayed significant neuroprotective effects (69.22 and 72.38% of cell viability, respectively) in the 6-hydroxydopamine-induced injury of the PC12 cell model (54.41%), comparable to the positive drug rasagiline (70.45%). The neuroprotective effect of 1 and 2 was further evidenced by the observation of the morphological change and fluorescein diacetate/propidium iodide staining. In addition, the levels of the major active compounds (1, 3, 5/6, and 16-18) vary from 21.5 to 892.3 μg/g. This is the first report on phenolic glycosides from the fruits ofL. ruthenicum Murr that possess both significant MAO-B inhibitory and neuroprotective effects, indicating the promising potential of the fruits for the development of health care products and even therapeutic agents for the treatment of Parkinson's disease and other neurodegenerative diseases.

Ligand fishing based on tubular microchannel modified with monoamine oxidase B for screening of the enzyme's inhibitors from Crocus sativus and Edgeworthia gardneri

A novel strategy of performing ligand fishing with enzyme-modified open tubular microchannel was proposed for screening bioactive components present in medicinal plants. Monoamine oxidase B was immobilized onto the surface of the microchannel for the first time to specifically extract its ligands when the plant's extracts solution flows through the channel. The thermal and the storage stability of immobilized monoamine oxidase B were significantly enhanced after immobilization. Crocin I and Ⅱ were extracted from Crocus sativus, and tiliroside was extracted from Edgeworthia gardneri. All the three compounds were inhibitors of the enzyme with the half-maximal inhibitory concentration values of 26.70 ± 0.91, 19.88 ± 2.78, and 15.65 ± 0.85 μM, respectively. The enzyme inhibition kinetics and molecular docking were investigated. This is the first report on the inhibitory effects of tiliroside and crocin Ⅱ. The novel ligand fishing method proposed in this work possesses advantages of rapidness, high efficiency, and tiny sample consumption compared to routine ligand fishing, with promising potential for screening active natural products in complex mixtures.

Fast screening of tyrosinase inhibitors from traditional Chinese medicinal plants by ligand fishing in combination with in situ fluorescent assay

A simple and rapid method for screening of tyrosinase (TYR) inhibitors present in traditional Chinese medicines (TCMs) was developed by combining ligand fishing and the fluorescent enzymatic assay based on dopamine-functionalized carbon quantum dots (CQDs-Dopa). Ligands of the enzyme present in the TCM extractions were firstly adsorbed on the enzyme-modified magnetic beads, and then the beads were magnetically separated and subjected directly to the CQDs-Dopa-based fluorescent assay. Finally, compounds were desorbed from the "active" beads and identified with ultra-performance liquid chromatography-triple quadrupole mass spectrometry. A known natural TYR inhibitor quercetin was selected to assess the feasibility and quantification performance of this method, and good linearity in the range of 0.01-0.16 mM (R² = 0.992) with a low detection limit of 0.004 mM was obtained. This method was then applied to screen TYR inhibitors present in Scutellaria baicalensis and Sophora flavescens. Six TYR inhibitors including baicalin (1), baicalein (2), wogonin (3), oroxylin A (4), kurarinone (5), and sophoraflavanone G (6) were found, among which 1-4 were firstly discovered in this work. This is the first report on the in situ assessment of the target compounds obtained by ligand fishing in the form of a mixture, which exhibited the combined advantages of specific extraction ability of ligand fishing and the high sensitivity of CQDs-based fluorescent assay, showing great potential for fast screening of enzyme inhibitors from TCMs.

Fishing of α-Glucosidase's Ligands from Aloe vera by α-Glucosidase Functionalized Magnetic Nanoparticles

α-Glucosidase was immobilized on magnetic nanoparticles (MNPs) for selective solid-phase extraction of the enzyme’s ligands present in Aloe vera, which is a medicinal plant used for the treatment of various diseases and possesses anti-diabetic activity. One new compound, aloeacone (2), together with two known compounds, aloenin aglycone (1) and aloin A (3), were fished out as the enzyme’s ligands. The structure of 2 was determined by HR-MS and comprehensive NMR techniques. Compound 3 exhibited a weak inhibitory effect on α-glucosidase, while compounds 1 and 2 were found to possess activation effects on the enzyme for the first time. It is interesting that both an inhibitor and agonists of α-glucosidase were fished out in one experiment.

Magnetic particles for enzyme immobilization: A versatile support for ligand screening

Enzyme inhibitors represent a substantial fraction of all small molecules currently in clinical use. Therefore, the early stage of drug-discovery process and development efforts are focused on the identification of new enzyme inhibitors through screening assays. The use of immobilized enzymes on solid supports to probe ligand-enzyme interactions have been employed with success not only to identify and characterize but also to isolate new ligands from complex mixtures. Between the available solid supports, magnetic particles have emerged as a promising support for enzyme immobilization due to the high superficial area, easy separation from the reaction medium and versatility. Particularly, the ligand fishing assay has been employed as a very useful tool to rapidly isolate bioactive compounds from complex mixtures, and hence the use of magnetic particles for enzyme immobilization has been widespread. Thus, this review provides a critical overview of the screening assays using immobilized enzymes on magnetic particles between 2006 and 2021.

Rapid Screening and Identification of Antitumor Ingredients from the Mangrove Endophytic Fungus Using an Enzyme-Immobilized Magnetic Nanoparticulate System

As a consequence of recent progression in biomedicine and nanotechnology, nanoparticle-based systems have evolved as a new method with extensive applications in responsive therapy, multimodal imaging, drug delivery and natural product separation. Meanwhile, the magnetic nanoparticulate system has aroused great interest for separation and purification because of its excellent magnetic properties. Phospholipase A₂ (PLA₂) is a highly expressed regulator to promote the growth of various cancers and is an ideal target to treat cancers. In this study, a novel strategy based on ligand–receptor interactions to discover novel PLA₂ inhibitors was established, in which PLA₂-functionalized Fe₃O₄@PLGA-PEG-NH₂ magnetic nanoparticles were used as a supporting material combined with high-performance liquid chromatography–mass spectrometry, aiming to accelerate the discovery of novel PLA₂ inhibitors from natural sources such as mangrove endophytic fungi. Under the optimized ligand fishing conditions, six target compounds were ultimately fished and identified to be cyclic peptides (1–3) and sterols (4–6), which compounds 1, 2 and 4–6 have well-documented cytotoxicities. Compound 3 exerted better inhibitory effect on A549 cells by experiment. In conclusion, PLA₂-functionalized Fe₃O₄@PLGA-PEG-NH₂ magnetic nanoparticles-based ligand fishing provided a feasible, selective and effective platform for the efficient screening and identification of antitumor components from natural products.

Recent applications of magnetic solid phase extraction in sample preparation for phytochemical analysis

Sample preparation such as isolation and pre-concentration is a crucial step for the phytochemical analysis. Magnetic solid-phase extraction (MSPE) has received considerable attention, mainly due to its phase separation more conveniently by facile magnetic decantation as compared to traditional SPE. This review focused on the recent applications of MSPE in sample preparation for the analysis of phytochemical compounds in plants, biological samples and Chinese herbal preparations. In addition, the enzymes immobilized on the magnetic materials and used for the biospecific extraction of enzyme inhibitors were also discussed. The information summarized in this article may provide a reference to the further applications of MSPE in phytochemical analysis.

Ligand Fishing: An Approach for the Discovery of Inhibitors from Complex Biological Mixtures

Ligand fishing is a convenient bioanalytical screening method that is based on the affinity selection of a ligand from a complex biological sample by an immobilized receptor. It is a versatile affinity-based screening approach and it has found application in multiple interacting pairs such as enzyme-inhibitor/activator, antigen-antibody, receptor-ligand, and protein-protein. Important parameters that affect the successful operation of the method are the high specificity and strong binding affinity of the interacting pair (e.g., enzyme-ligand complex) and the elution of the bound ligand from the complex. This chapter provides protocols for the synthesis of affinity adsorbent and its application in off-line ligand-fishing procedure for a 6His-tagged glutathione transferase (GST).

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.