An ultrafiltration and high performance liquid chromatography coupled with diode array detector and mass spectrometry approach for screening and characterizing thrombin inhibitors from Rhizoma Chuanxiong

Magnetic nanoparticles immobilized thrombin ligand fishing to screen thrombin inhibitors in natural products

In this study, thrombin was immobilized with magnetic particles modified by glutaraldehyde. The changes in secondary structures of immobilized enzyme revealed an increment in conformational rigidity and stability, which can be reflected in temperature and pH stability as well as the tolerance of organic reagents. The optimal reutilization times of magnetic particle immobilized thrombin were 7 times, and the half-life of enzyme activity preserved at room temperature was 5 days, which was 2.5 times higher than that of free enzyme. Ligusticum chuanxiong and Anemarrhenae Rhizoma with high enzyme inhibitory activity were selected for primary screening, and six potential inhibitors of thrombin were identified by HPLC/MS. The results showed that three compounds in Anemarrhenae Rhizoma had better predictive thrombin inhibitory activity. Through the in vitro thrombin activity inhibition experiment, it was also verified that mangiferin and neo-mangiferin had an ideal thrombin activity inhibition effect, which was consistent with the results of molecular docking.

Potential anticoagulant of traditional chinese medicine and novel targets for anticoagulant drugs

BACKGROUND

Anticoagulants are the main drugs used for the prevention and treatment of thrombosis. Currently, anticoagulant drugs are primarily multitarget heparin drugs, single-target FXa inhibitors and FIIa inhibitors. In addition, some traditional Chinese drugs also have anticoagulant effects, but they are not the main direction of treatment at present. But the anticoagulant drugs mentioned above, all have a common side effect is bleeding. Many other anticoagulation targets are under investigation. With further exploration of coagulation mechanism, how to further determine new anticoagulant targets and how to make traditional Chinese medicine play anticoagulant role have become a new field of exploration.

PURPOSE

The purpose of the study was to summarize the recent research progress on coagulation mechanisms, new anticoagulant targets and traditional Chinese medicine.

METHODS

A comprehensive literature search was conducted using four electronic databases, including PubMed, Embase, CNKI, Wanfang database and ClinicalTrials.gov, from the inception of the study to 28 Feb 2023. Key words used in the literature search were "anticoagulation", "anticoagulant targets", "new targets", "coagulation mechanisms", "potential anticoagulant", "herb medicine", "botanical medicine", "Chinese medicine", "traditional Chinese medicine", "blood coagulation factor", keywords are linked with AND/OR. Recent findings on coagulation mechanisms, potential anticoagulant targets and traditional Chinese medicine were studied.

RESULTS

The active components extracted from the Chinese medicinal herbs, Salvia miltiorrhiza, Chuanxiong rhizoma, safflower and Panax notoginseng have obvious anticoagulant effects and can be used as potential anticoagulant drugs, but the risk of bleeding is unclear. TF/FVIIa, FVIII, FIX, FXI, FXII, and FXIII have all been evaluated as targets in animal studies or clinical trials. FIX and FXI are the most studied anticoagulant targets, but FXI inhibitors have shown stronger advantages.

CONCLUSION

This review of potential anticoagulants provides a comprehensive resource. Literature analysis suggests that FXI inhibitors can be used as potential anticoagulant candidates. In addition, we should not ignore the anticoagulant effect of traditional Chinese medicine, and look forward to more research and the emergence of new drugs.

Senkyunolide I: A Review of Its Phytochemistry, Pharmacology, Pharmacokinetics, and Drug-Likeness

Senkyunolide I (SI) is a natural phthalide that has drawn increasing interest for its potential as a cardio-cerebral vascular drug candidate. In this paper, the botanical sources, phytochemical characteristics, chemical and biological transformations, pharmacological and pharmacokinetic properties, and drug-likeness of SI are reviewed through a comprehensive literature survey, in order to provide support for its further research and applications. In general, SI is mainly distributed in Umbelliferae plants, and it is relatively stable to heat, acid, and oxygen, with good blood-brain barrier (BBB) permeability. Substantial studies have established reliable methods for the isolation, purification, and content determination of SI. Its pharmacological effects include analgesic, anti-inflammatory, antioxidant, anti-thrombotic, anti-tumor effects, alleviating ischemia-reperfusion injury, etc. Pharmacokinetic parameters indicate that its metabolic pathway is mainly phase Ⅱ metabolism, and it is rapidly absorbed in vivo and widely distributed in the kidneys, liver, and lungs.

Potential Antioxidative and Anti-Hyperuricemic Components Targeting Superoxide Dismutase and Xanthine Oxidase Explored from Polygonatum Sibiricum Red

Polygonatum sibiricum Red. (P. sibiricum) has been used as a traditional Chinese medicine with a wide range of pharmacology effects. However, the responsible bioactive compounds and their mechanisms of action concerning its antioxidative and anti-hyperuricemic activities remain unexplored. In this work, the antioxidant capacity of P. sibiricum was firstly evaluated with the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azinobis-(3ethylbenzthiazoline)-6-sulfonic acid (ABTS) and ferric-reducing antioxidant power (FRAP) assays, from which the ethyl acetate (EA) fraction exhibited the highest DPPH, ABTS radical scavenging, and ferric-reducing capacities. Meanwhile, the EA fraction displayed the highest total phenolic and flavonoid contents among the four fractions. Next, the potential ligands from the EA fraction were screened out by bio-affinity ultrafiltration liquid chromatography-mass spectrometry (UF-LC-MS) with superoxide dismutase (SOD) and xanthine oxidase (XOD). As a result, N-trans-p-coumaroyloctopamine, N-trans-feruloyloctopamine, N-trans-feruloyltyramine were identified as potential SOD ligands, while N-cis-p-coumaroyltyramine was determined as potential XOD ligand. Additionally, these four ligands effectively interact with SOD and XOD in the molecular docking analysis, with binding energies (BEs) ranging from –6.83 to –6.51 kcal/mol, and the inhibition constants (Ki) from 9.83 to 16.83 μM, which were better than the positive controls. In conclusion, our results indicated that P. sibiricum has good antioxidative and anti-hyperuricemic activities, and its corresponding active ligands targeting SOD and XOD could be explored by the UF-LC-MS method.

Potential clinical applications of phytopharmaceuticals for the in-patient management of coagulopathies in COVID-19

Thrombotic complications occur in many cardiovascular pathologies and have been demonstrated in COVID‐19. The currently used antithrombotic drugs are not free of adverse reactions, and COVID‐19 patients in particular, when treated with a therapeutic dose of an anticoagulant do not receive mortality benefits. The clinical management of COVID‐19 is one of the most difficult tasks for clinicians, and the search for safe, potent, and effective antithrombotic drugs may benefit from exploring naturally bioactive molecules from plant sources. This review describes recent advances in understanding the antithrombotic potential of herbal drug prototypes and points to their future clinical use as potent antithrombotic drugs. Although natural products are perceived to be safe, their clinical and therapeutic applications are not always apparent or accepted. More in‐depth studies are necessary to demonstrate the clinical usefulness of plant‐derived, bioactive compounds. In addition, holistic approaches in systematic investigations and the identification of antithrombotic mechanisms of the herbal bioactive molecule(s) need to be conducted in pre‐clinical studies. Moreover, rigorous studies are needed to compare the potency of herbal drugs to that of competitor chemical antithrombotic drugs, and to examine their interactions with Western antithrombotic medicines. We have also proposed a road map to improve the commercialization of phytopharmaceuticals.

Research Advances in Cardio-Cerebrovascular Diseases of Ligusticum chuanxiong Hort

Cardio-cerebrovascular diseases (CVDs) are a serious threat to human health and account for 31% of global mortality. Ligusticum chuanxiong Hort. (CX) is derived from umbellifer plants. Its rhizome, leaves, and fibrous roots are similar in composition but have different contents. It has been used in Japanese, Korean, and other traditional medicine for over 2000 years. Currently, it is mostly cultivated and has high safety and low side effects. Due to the lack of a systematic summary of the efficacy of CX in the treatment of CVDs, this article describes the material basis, molecular mechanism, and clinical efficacy of CX, as well as its combined application in the treatment of CVDs, and has been summarized from the perspective of safety. In particular, the pharmacological effect of CX in the treatment of CVDs is highlighted from the point of view of its mechanism, and the complex mechanism network has been determined to improve the understanding of CX's multi-link and multi-target therapeutic effects, including anti-inflammatory, antioxidant, and endothelial cells. This article offers a new and modern perspective on the impact of CX on CVDs.

Exploring the Potential Mechanism of Chuanxiong Rhizoma Treatment for Migraine Based on Systems Pharmacology

Migraine is a disease whose aetiology and mechanism are not yet clear. Chuanxiong Rhizoma (CR) is employed in traditional Chinese medicine (TCM) to treat various disorders. CR is effective for migraine, but its active compounds, drug targets, and exact molecular mechanism remain unclear. In this study, we used the method of systems pharmacology to address the above issues. We first established the drug-compound-target-disease (D-C-T-D) network and protein-protein interaction (PPI) network related to the treatment of migraine with CR and then established gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The results suggest that the treatment process may be related to the regulation of inflammation and neural activity. The docking results also revealed that PTGS2 and TRPV1 could directly bind to the active compounds that could regulate them. In addition, we found that CR affected 11 targets that were more highly expressed in the liver or heart but were the lowest in the whole brain. It also expounds the description of CR channel tropism in TCM theory from these angles. These findings not only indicate that CR can be developed as a potential effective drug for the treatment of migraine but also demonstrate the application of systems pharmacology in the discovery of herbal-based disease therapies.

Identifying of Anti-Thrombin Active Components From Curcumae Rhizoma by Affinity-Ultrafiltration Coupled With UPLC-Q-Exactive Orbitrap/MS

Recent studies concerning products that originate from natural plants have sought to clarify active ingredients, which both explains the mechanisms of the function and aids in quality control during production. As a traditional functional plant, Curcumae Rhizoma (CR) has been proven to be effective in promoting blood circulation and removing blood stasis. However, the components that play a role in its huge compound library are still unclear. The present study aimed to develop a high-throughput screening method to identify thrombin inhibitors in CR and validate them by in vitro and in vivo experiments. The effect of CR on thrombin in HUVECs cells was determined by ELISA, then an affinity-ultrafiltration-UPLC-Q-Exactive Orbitrap/MS approach was applied. Agatroban and adenosine were used as positive and negative drugs respectively to verify the reliability of the established method. The in vitro activity of the compounds was determined by specific substrate S-2238. The in vivo effect of the active ingredients was determined using zebrafish. Molecular docking was used to understand the internal interactions between compounds and enzymes. ELISA results showed that CR had an inhibitory effect on thrombin. The screening method established in this paper is reliable, by which a total of 15 active compounds were successfully identified. This study is the first to report that C7, 8, and 11 have in vitro thrombin-inhibitory activity and significantly inhibit thrombosis in zebrafish models at a safe dose. Molecular docking studies were employed to analyze the possible active binding sites, with the results suggesting that compound 16 is likely a better thrombin inhibitor compared with the other compounds. Based on the affinity-ultrafiltration-UPLC-Q-Exactive Orbitrap/MS approach, a precisely targeted therapy method using bio-active compounds from CR might be successfully established, which also provides a valuable reference for targeted therapy, mechanism exploration, and the quality control of traditional herbal medicine.

Simultaneously screening multiple UGT1A1 inhibitors from Polygonum multiflorum root using ultrafiltration liquid chromatography-mass spectrometry

The liver injury induced by Polygonum multiflorum root (PMR) is an urgent issue requiring wide spread attention. UDP-glucuronosyltransferase 1A1 (UGT1A1) inhibitors are suspected to additively contribute to the hepatotoxicity of PMR. This study was deliberately designed to simultaneously screen the UGT1A1 inhibitors from PMR and their co-contribution to the hepatotoxicity was evaluated. With ultrafiltration coupled to liquid chromatography-mass spectrometry method, four compounds namely cis-2,3,5,4'-tetrahydroxystilbene-2-O-β-glucoside, trans-2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, emodin-8-O-β-D-glucoside and emodin were screened out, displaying the in vitro inhibitory activities against UGT1A1 with IC₅₀ values of 76.23, 18.70, 62.18, 34.02 μM, respectively. The varying activities of screened UGT1A1 inhibitors were explained by performing a molecular docking simulation. Finally, zebrafish larvae and mice assays demonstrated that the UGT1A1 inhibitors co-contributed to the hepatotoxicity of PMR. Hopefully, these findings are conducive to understand the acting role of UGT1A1 inhibitors in PMR-induced hepatotoxicity.

Rapid screening and identification of anticoagulation component from carthami flos by two-dimensional thrombin affinity chromatography combined with HPLC-MS/MS

Carthami flos, commonly known as Honghua in China, is the dried floret of safflower and widely acknowledged as a blood stasis promoting herb. The study aimed at investigating the relationship between thrombin and carthami flos through a high-performance thrombin affinity chromatography combined with a high-performance liquid chromatography-tandem mass spectrometry system. First, thrombin was immobilized on the glutaraldehyde-modified amino silica gel to prepare the thrombin affinity stationary phase, which was packed into a small column (1.0 × 2.0 mm, id) for recognizing the anticoagulant active components of carthami flos. The target component was enriched and analyzed by the high-performance liquid chromatography-tandem mass spectrometry system. Finally, hydroxysafflor yellow A was screened out and identified as the active component. The anticoagulant effects of hydroxysafflor yellow A were analyzed by anticoagulant experiments in vitro, and the interaction of hydroxysafflor yellow A with thrombin was investigated by the molecular docking method. The results proved that hydroxysafflor yellow A (30 μg/mL, 0.05 mM) and carthami flos extract (30 μg/mL) could prolong activated partial thrombin time and thrombin time by 50 and 11%, respectively. Moreover, hydroxysafflor yellow A exhibits a good hydrogen bond field and stereo field matching with thrombin. Overall, it was concluded that hydroxysafflor yellow A might exert an anticoagulation effect by interacting with thrombin and thus could be potential anticoagulant drugs for the prevention and treatment of venous thrombosis.

Affinity ultrafiltration and UPLC-HR-Orbitrap-MS based screening of thrombin-targeted small molecules with anticoagulation activity from Poecilobdella manillensis

This study aims to screen potential anticoagulant components from leeches, a representative animal-sourced traditional Chinese medicine using thrombin (THR)-targeted ultrafiltration combined with ultrahigh performance liquid chromatography and high-resolution Orbitrap mass spectrometry (UPLC-HR-Orbitrap-MS). As a result, five small molecules in leech extract were discovered to interact with THR for the first time. Among them, two new compounds were isolated and their structures were identified by IR, HR-MS and NMR data. Furthermore, their THR inhibitory activity was confirmed with IC₅₀ values of 4.74 and 8.31 μM, respectively. In addition, molecular docking analysis showed that the active (catalytic) site of THR might be the possible binding site of the two hits. Finally, reverse screening analysis indicated that LTA4-H, ACE and ALOX5AP were potential anticoagulant targets of the two new compounds. This study will broaden our understanding of the medicinal substance basis in leeches and further contribute to the discovery and development of clinical anticoagulant drugs from leeches.

Affinity selection-mass spectrometry for the discovery of pharmacologically active compounds from combinatorial libraries and natural products

Invented to address the high-throughput screening (HTS) demands of combinatorial chemistry, affinity selection-mass spectrometry (AS-MS) utilizes binding interactions between ligands and receptors to isolate pharmacologically active compounds from mixtures of small molecules and then relies on the selectivity, sensitivity, and speed of mass spectrometry to identify them. No radiolabels, fluorophores, or chromophores are required. Although many variations of AS-MS have been devised, three approaches have emerged as the most flexible, productive, and popular, and they differ primarily in how ligand-receptor complexes are separated from nonbinding compounds in the mixture. These are pulsed ultrafiltration (PUF) AS-MS, size exclusion chromatography (SEC) AS-MS, and magnetic microbead affinity selection screening (MagMASS). PUF and SEC AS-MS are solution-phase screening approaches, and MagMASS uses receptors immobilized on magnetic microbeads. Because pools of compounds are screened using AS-MS, each containing hundreds to thousands of potential ligands, hundreds of thousands of compounds can be screened per day. AS-MS is also compatible with complex mixtures of chemically diverse natural products in extracts of botanicals and fungi and microbial cultures, which often contain fluorophores and chromophores that can interfere with convention HTS. Unlike conventional HTS, AS-MS may be used to discover ligands binding to allosteric as well as orthosteric receptor sites, and AS-MS has been useful for discovering ligands to targets that are not easily incorporated into conventional HTS such as membrane-bound receptors.

LABEL-FREE BIO-AFFINITY MASS SPECTROMETRY FOR SCREENING AND LOCATING BIOACTIVE MOLECULES

Despite the recent increase in the development of bioactive molecules in the drug industry, the enormous chemical space and lack of productivity are still important issues. Additional alternative approaches to screen and locate bioactive molecules are urgently needed. Label-free bio-affinity mass spectrometry (BA-MS) provides opportunities for the discovery and development of innovative drugs. This review provides a comprehensive portrayal of BA-MS techniques and of their applications in screening and locating bioactive molecules. After introducing the basic principles, alongside some application notes, the current state-of-the-art of BA-MS-assisted drug discovery is discussed, including native MS, size-exclusion chromatography-MS, ultrafiltration-MS, solid-phase micro-extraction-MS, and cell membrane chromatography-MS. Finally, several challenges and limitations of the current methods are summarized, with a view to potential future directions for BA-MS-assisted drug discovery. © 2019 John Wiley & Sons Ltd. Mass Spec Rev.

Screening of β-secretase inhibitors from Dendrobii Caulis by covalently enzyme-immobilized magnetic beads coupled with ultra-high-performance liquid chromatography

In the present study, to effectively discover potential β-secretase inhibitors from Dendrobii Caulis, β-secretase was immobilized on magnetic beads via direct covalent connection and coupled with ultra-high-performance liquid chromatography. Mechanochemical-assisted extraction was used to extract active ingredients from Dendrobii Caulis. The main reaction conditions, including screening enzyme inhibitors, were evaluated, and the most important enzyme kinetic parameters were also investigated across the UV-vis spectrophotometer. Five compounds (rutin, scoparone, naringenin, dendrophenol, and erianin) with high binding affinity to magnetic beads were removed from the extract. The results indicated that β-secretase was successfully immobilized and screened out five potential inhibitor compounds by ligand fishing. The lowest IC₅₀ values were noted for rutin (5.437 μM) and erianin (2.039 μM). This is the first report on immobilized β-secretase on magnetic beads for the identification of potential active compounds against Alzheimer's disease from complex biological mixtures.

Adsorbed hollow fiber immobilized tyrosinase for the screening of enzyme inhibitors from Pueraria lobata extract

In this study, a method based on adsorbed hollow fiber immobilized tyrosinase (TYR) was developed to screening potential TYR inhibitors from Pueraria lobate extract. Kojic acid and ranitidine were used as positive and negative control to verify the reliability of the proposed method, respectively. Several significant parameters of the screening process, including the amount of P. lobata extract, adsorption time and incubation time, were optimized. After investigating the repeatability of the developed method, seven potential active compounds in P. lobata extract were successfully detected and their chemical structures were tentatively identified by liquid chromatography - mass spectrometry analysis. Furthermore, the inhibitory activity of four identified compounds on TYR was tested in vitro, and three of them, namely, puerarin, puerarin-6″-O-xyloside and puerarin apioside were verified to have good TYR inhibitory activity with IC₅₀ value of 478.5, 513.8, and 877.3 μM, respectively. In addition, the molecular docking results indicated that these compounds could bind to the amino acid residues in TYR catalytic pocket. These results proved that the proposed method is a feasible approach for screening of TYR inhibitors from plant extract.

Characterization of thrombin/factor Xa inhibitors in Rhizoma Chuanxiong through UPLC-MS-based multivariate statistical analysis

Background

The dry root and rhizome of Ligusticum chuanxiong Hort., or Chuanxiong, has been used as a blood-activating and stasis-removing traditional Chinese medicine for 1000 years. Our previous studies have shown the inhibitory activity on platelet and thrombin (THR) of Chuanxiong. THR and factor Xa (FXa) play significant roles in the coagulation cascade and their inhibitors are of valuable in the treatment of thromboembolic diseases. The aim of the present study is to screen THR and FXa inhibitors from Chuanxiong.

Methods

Four extracts [ethyl acetate (EA), butanol (BA) and remained extract (RE) from 75% ethanol extract, and water extract (WE)] of Chuanxiong were prepared, and their THR/FXa inhibitory activities were assessed in vitro. Following silica-gel column chromatography (SC), the active EA extract and BA extract was further partitioned, respectively. Their active fractions (EA-SC1 to EA-SC5; BA-SC1 to BA-SC5) were obtained and analyzed by LC–MS. After modeling by the principal component analysis (PCA) and orthogonal partial least squares discriminate analysis (OPLS-DA), the specific marker compounds were predicted and identified. Their enzyme inhibitory was assessed in vitro and interactions with THR/FXa were investigated by molecular docking analysis.

Results

Chuanxiong EA extract showed strong activity against THR and BA extract was more effective in inhibiting FXa activity, and their fractions exhibited obvious difference in enzyme inhibitory activity. Furthermore, marker compounds a–h were predicted by PCA and OPLS-DA, and their chemical structures were identified. Among them, senkyunolide A, Z-ligustilide, ferulic acid and senkyunolide I (IC₅₀ was determined as 0.77 mM) with potential THR inhibitory activity, as well as isochlorogenic acid A with FXa inhibitory activity were screened out. It was found that the four components could interact with the active site of THR, and the binding energy was lower than − 5 kcal/mol. Isochlorogenic acid A were bound to the active site of FXa, and the binding energy was − 9.39 kcal/mol. The IC₅₀ was determined as 0.56 mM.

Conclusions

THR/FXa inhibitory components in different extracts of Chuanxiong were successfully characterized by the method of enzyme inhibition activity assays with ultra performance liquid chromatography-quadrupole time of flight mass spectrometry-based multivariate statistical analysis.

Sample preparation techniques for protein binding measurement in radiopharmaceutical approaches: A short review

Plasma protein binding (PPB) measurement is a key step in radiopharmaceutical studies for the development of positron emission tomography (PET) radioligands. PPB refers to the binding degree of a radioligand, radiotracer, or drug to blood plasma proteins or tissues after administration into the body. Several techniques have been successfully developed and applied for PPB measurement of PET radioligands. However, there is room for progress among these techniques in relation to duration time, adaptability with nonpolar radioligands, in vivo measurement, specificity, and selectivity. This mini review gives a brief overview of advances, limitations, and prospective applications of commercially-available PPB methods.

A novel thrombin inhibitory peptide discovered from leech using affinity chromatography combined with ultra-high performance liquid chromatography-high resolution mass spectroscopy

Thrombin (THR) inhibitors play an important role in the treatment of thrombotic diseases. This study established a THR-based bio-specific extraction coupled with affinity chromatography and ultra-high performance liquid chromatography-high resolution mass spectroscopy (UPLC-HR-MS) analysis method to screen and identify THR ligands in Leech. After evaluating the reliability of the screening method using positive control drug (hirudin), it was successfully used to screen the potential active constituents in leech. And a comprehensive analysis of the peptides in leech elution was performed by UPLC-HR-MS, a total of 34 peptides were identified. At the same time, anti-THR activity was explored and inferred by searching databases and published literature. As a result, six peptides were discovered to be potential active compounds in leech. Further, the six peptides were synthesized and in vitro enzymatic activity assay was performed. Finally, SYELPDGQVITIGNER was screened as an anti-THR peptide with an IC50 value of 255.75 µM and it was discovered for the first time from Whitmania pigra Whitman and Hirudo nipponica Whitman. The molecular docking study showed that THR inhibitory activity of the polypeptide was mainly attributed to the hydrogen bond interactions, van der Waals forces and electrostatic interactions interaction between polypeptide and THR. These results suggest that the polypeptide is a potential natural THR inhibitor that can be used as anticoagulant.

LC-MS-based multivariate statistical analysis for the screening of potential thrombin/factor Xa inhibitors from Radix Salvia Miltiorrhiza

Background

The dry root and rhizome of Salvia miltiorrhiza Bunge, or Danshen, is a well-known traditional Chinese medicine with anticoagulant activity. Taking into account that thrombin (THR) and factor Xa (FXa) play crucial roles in the coagulation cascade, it is reasonable and meaningful to screening THR and/or FXa inhibitors from Danshen.

Methods

Four extracts [butanol (BA), ethyl acetate (EA) and remained extract (RE) from 75% ethanol extract, and water extract (WE)] of Danshen were prepared, and their THR/FXa inhibitory activities were assessed in vitro. Then, the active EA extract was further separated by silica-gel column chromatography (SC), and its fractions (SC1–SC5) were analyzed by LC–MS. The principal component analysis (PCA) and orthogonal partial least squares discriminate analysis (OPLS-DA) were employed for predicting the specific marker compounds. The chemical structures of targeted compounds were identified by LC–MS/MS and their interactions with THR/FXa were analyzed by the molecular docking analysis.

Results

Danshen EA extract showed strong activity against THR and FXa, and its fractions (SC1–SC5) exhibited obvious difference in inhibitory activity against these two enzymes. Furthermore, four marker compounds with potential THR/FXa inhibitory activity were screened by PCA and OPLS-DA, and were identified as cryptotanshinone, tanshinone I, dihydrotanshinone I and tanshinone IIA. The molecular docking study showed that all these four tanshinones can interact with some key amino acid residues of the THR/FXa active cavities, such as HIS57 and SER195, which were considered to be promising candidates targeting THR and/or FXa with low binding energy (< − 7 kcal mol⁻¹).

Conclusions

LC–MS combined with multivariate statistical analysis can effectively screen potential THR/FXa inhibitory components in Danshen.

Anthraquinones from Cassiae semen as thrombin inhibitors: in vitro and in silico studies

Thrombin inhibitor therapy is one of the most effective therapeutic strategies for the prevention and treatment of cardiovascular and thrombotic diseases. Although several marketed direct thrombin inhibitors (DTIs) have been widely used in clinic, the potentially serious complications of these DTIs prompted the researchers to find more DTIs with improved safety profiles. Herein, we report that natural anthraquinones in Cassiae semen (the seed of Cassia obtusifolia L. or C. tora L.), including obtusifolin, obtusin, aurantio-obtusin and chryso-obtusin, display strong to moderate inhibition on human thrombin, with the IC₅₀ values ranging from 9.08 μM to 27.88 μM. Further investigation on the inhibition kinetics demonstrates that these anthraquinones are mixed inhibitors against thrombin-mediated Z-GGRAMC acetate hydrolysis, while obtusifolin and aurantio-obtusin show strong thrombin inhibition capacity, with the K_i values of 9.63 μM and 10.30 μM, respectively. Docking simulations demonstrate that both obtusifolin and aurantio-obtusin can simultaneously bind on the catalytic cavity and the two anion binding exosites (ABE1 and ABE2), while the hydroxyl group at the C-7 site and the methoxyl group at the C-8 site can create key interactions with the amino acids surrounding the catalytic cavity via hydrogen bonding. All these findings suggest that obtusifolin and aurantio-obtusin are strong thrombin inhibitors possessing a unique anthraquinone skeleton, and could be used as lead compounds for the development of new thrombin inhibitors with improved properties.

Rapid screening and identification of bioactive compounds specifically binding to beta 2-adrenoceptor from San-ao decoction using affinity magnetic fine particles coupled with high-performance liquid chromatography-mass spectrometry

Background

San-ao decoction (SAD) has been widely used in Chinese medicine against respiratory diseases, such as asthma and rhinallergosis. The bioactive compounds for such pharmacological action remain unknown.

Methods

We developed a methodology to isolate the bioactive compounds of SAD. The assay involved the immobilization of beta 2-adrenoceptor (β ₂-AR) onto magnetic fine particles, the capture of target compounds by the immobilized receptor, the identification of the receptor bound compounds by reversed-phase high-performance liquid chromatography coupled with tandem mass spectrometry.

Results

Vicenin, shaftoside, isoshaftoside, liquiritin apioside and isoliquiritin apioside were identified as β ₂-AR ligands in SAD extract. The binding of these compounds to β ₂-AR occurred on serine¹⁶⁹, serine¹⁷⁰ and phenylalanine²⁵⁶ of the receptor.

Conclusions

The developed methodology has high stability and specificity for recognizing and isolating target compounds. It is an alternative method for rapidly screening bioactive compounds of immobilized receptor from Chinese prescriptions.

MS methods to study macromolecule-ligand interaction: Applications in drug discovery

The interaction of small compounds (i.e. ligands) with macromolecules or macromolecule assemblies (i.e. targets) is the mechanism of action of most of the drugs available today. Mass spectrometry is a popular technique for the interrogation of macromolecule-ligand interactions and therefore is also widely used in drug discovery and development. Thanks to its versatility, mass spectrometry is used for multiple purposes such as biomarker screening, identification of the mechanism of action, ligand structure optimization or toxicity assessment. The evolution and automation of the instruments now allows the development of high throughput methods with high sensitivity and a minimized false discovery rate. Herein, all these approaches are described with a focus on the methods for studying macromolecule-ligand interaction aimed at defining the structure-activity relationships of drug candidates, along with their mechanism of action, metabolism and toxicity.

Investigation of Interactions between Thrombin and Ten Phenolic Compounds by Affinity Capillary Electrophoresis and Molecular Docking

Thrombin plays a vital role in blood coagulation, which is a key process involved in thrombosis by promoting platelet aggregation and converting fibrinogen to form the fibrin clot. In the receptor concept, drugs produce their therapeutic effects via interactions with the targets. Therefore, investigation of interaction between thrombin and small molecules is important to find out the potential thrombin inhibitor. In this study, affinity capillary electrophoresis (ACE) and in silico molecular docking methods were developed to study the interaction between thrombin and ten phenolic compounds (p-hydroxybenzoic acid, protocatechuic acid, vanillic acid, gallic acid, catechin, epicatechin, dihydroquercetin, naringenin, apigenin, and baicalein). The ACE results showed that gallic acids and six flavonoid compounds had relative strong interactions with thrombin. In addition, the docking results indicated that all of optimal conformations of the six flavonoid compounds were positioned into the thrombin activity centre and had interaction with the HIS57 or SER195 which was the key residue to bind thrombin inhibitors such as argatroban. Herein, these six flavonoid compounds might have the potential of thrombin inhibition activity. In addition, the developed method in this study can be further applied to study the interactions of other molecules with thrombin.