Flavonoids inhibit the amidolytic activity of human thrombin

Carbonization of quercetin into nanogels: a leap in anticoagulant development

Quercetin, a flavonoid abundantly found in onions, fruits, and vegetables, is recognized for its pharmacological potential, especially for its anticoagulant properties that work by inhibiting thrombin and coagulation factor Xa. However, its clinical application is limited due to poor water solubility and bioavailability. To address these limitations, we engineered carbonized nanogels derived from quercetin (CNGsQur) using controlled pyrolysis and polymerization techniques. This led to substantial improvements in its anticoagulation efficacy, water solubility, and biocompatibility. We generated a range of CNGsQur by subjecting quercetin to varying pyrolytic temperatures and then assessed their anticoagulation capacities both in vitro and in vivo. Coagulation metrics, including thrombin clotting time (TCT), activated partial thromboplastin time (aPTT), and prothrombin time (PT), along with a rat tail bleeding assay, were utilized to gauge the efficacy. CNGsQur showed a pronounced extension of coagulation time compared to uncarbonized quercetin. Specifically, CNGsQur synthesized at 270 °C (CNGsQur270) exhibited the most significant enhancement in TCT, with a binding affinity to thrombin exceeding 400 times that of quercetin. Moreover, variants synthesized at 310 °C (CNGsQur310) and 290 °C (CNGsQur290) showed the most substantial delays in PT and aPTT, respectively. Our findings indicate that the degree of carbonization significantly influences the transformation of quercetin into various CNGsQur forms, each affecting distinct coagulation pathways. Additionally, both intravenous and oral administrations of CNGsQur were found to extend rat tail bleeding times by up to fivefold. Our studies also demonstrate that CNGsQur270 effectively delays and even prevents FeCl3-induced vascular occlusion in a dose-dependent manner in mice. Thus, controlled pyrolysis offers an innovative approach for generating quercetin-derived CNGs with enhanced anticoagulation properties and water solubility, revealing the potential for synthesizing self-functional carbonized nanomaterials from other flavonoids for diverse biomedical applications.

Effects of Rheum rhaponticum and Rheum rhabarbarum extracts on haemostatic activity of blood plasma components and endothelial cells in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional medicine recommends the use of Rheum rhaponticum L. and R. rhabarbarum L. to treat over thirty complaints, including disorders related to the cardiovascular system such as heartache, pains in the pericardium, epistaxis and other types of haemorrhage, blood purification as well as disorders of venous circulation.

AIM OF THE STUDY

This work was dedicated to examining for the first time the effects of extracts from petioles and roots of R. rhaponticum and R. rhabarbarum, as well as two stilbene compounds (rhapontigenin and rhaponticin) on the haemostatic activity of endothelial cells and functionality of blood plasma components of the haemostatic system.

MATERIALS AND METHODS

The study was based on three main experimental modules, including the activity of proteins of the human blood plasma coagulation cascade and the fibrinolytic system as well as analyses of the haemostatic activity of human vascular endothelial cells. Additionally, interactions of the main components of the rhubarb extracts with crucial serine proteases of the coagulation cascade and fibrinolysis (i.e. thrombin, the coagulation factor Xa and plasmin) were analyzed in silico.

RESULTS

The examined extracts displayed anticoagulant properties and significantly reduced the tissue factor-induced clotting of human blood plasma (by about 40%). Inhibitory effects of the tested extracts on thrombin and the coagulation factor Xa (FXa) were found as well. For the extracts, the IC₅₀ was ranging from 20.26 to 48.11 μg/ml. Modulatory effects on the haemostatic response of endothelial cells, including the release of von Willebrand factor, tissue-type plasminogen activator and the plasminogen activator inhibitor-1, have been also found.

CONCLUSIONS

Our results indicated for the first time that the examined Rheum extracts influenced the haemostatic properties of blood plasma proteins and endothelial cells, with the prevalence of the anticoagulant action. The anticoagulant effect of the investigated extracts may be partly attributed to the inhibition of the FXa and thrombin activities, the key serine proteases of the blood coagulation cascade.

Plant-Derived Compounds and Extracts as Modulators of Plasmin Activity-A Review

Functionality of the fibrinolytic system is based on activity of its central enzyme, plasmin, responsible for the removal of fibrin clots. Besides the hemostasis, fibrinolytic proteins are also involved in many other physiological and pathological processes, including immune response, extracellular matrix degradation, cell migration, and tissue remodeling. Both the impaired and enhanced activity of fibrinolytic proteins may result in serious physiological consequences: prothrombotic state or excessive bleeding, respectively. However, current medicine offers very few options for treating fibrinolytic disorders, particularly in the case of plasmin inhibition. Although numerous attempts have been undertaken to identify natural or to develop engineered fibrinolytic system modulators, structural similarities within serine proteases of the hemostatic system and pleiotropic activity of fibrinolytic proteins constitute a serious problem in discovering anti- or profibrinolytic agents that could precisely affect the target molecules and reduce the risk of side effects. Therefore, this review aims to present a current knowledge of various classes of natural inhibitors and stimulators of the fibrinolytic system being well-defined low-molecular plant secondary metabolites or constituents of plant extracts as well as plant peptides. This work also discusses obstacles caused by low specificity of most of natural compounds and, hence, outlines recent trends in studies aimed at finding more efficient modulators of plasmin activity, including investigation of modifications of natural pharmacophore templates.

A critical evaluation of risk to reward ratio of quercetin supplementation for COVID-19 and associated comorbid conditions

The interim results of the large, multinational trials on coronavirus disease 2019 (COVID‐19) using a combination of antiviral drugs appear to have little to no effect on the 28‐day mortality or the in‐hospital course. Therefore, there is a still vivid interest in finding alternate re‐purposed drugs and nutrition supplements, which can halt or slow the disease severity. We review here the multiple preclinical studies, partially supported by clinical evidence showing the quercetin's possible therapeutic/prophylaxis efficacy against severe acute respiratory syndrome coronavirus (SARS‐CoV) as well as comorbidities like chronic obstructive pulmonary disease (COPD), diabetes mellitus, obesity, coagulopathy, and hypertension. Currently, 14 interventional clinical trials are underway assessing the efficacy of quercetin along with other antiviral drugs/nutritional supplements as prophylaxis/treatment option against COVID‐19. The present review is tempting to suggest that, based on circumstantial scientific evidence and preliminary clinical data, the flavonoid quercetin can ameliorate COVID‐19 infection and symptoms acting in concert on two parallel and independent paths: inhibiting key factors responsible for SARS‐CoV‐2 infections and mitigating the clinical manifestations of the disease in patients with comorbid conditions. Despite the broad therapeutic properties of quercetin, further high power randomized clinical trials are needed to firmly establish its clinical efficacy against COVID‐19.

The Bioflavonoids Rutin and Rutin Succinate Neutralize the Toxins of B. jararaca Venom and Inhibit its Lethality

The venom of the Brazilian pit viper Bothrops jararaca (BjV) is a complex mixture of molecules, and snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) are the most abundant protein families found therein. Toxins present in BjV trigger most of the deleterious disturbances in hemostasis observed in snakebites, i.e., thrombocytopenia, hypofibrinogenemia and bleedings. The treatment of patients bitten by snakes still poses challenges and the bioflavonoid rutin has already been shown to improve hemostasis in an experimental model of snakebite envenomation. However, rutin is poorly soluble in water; in this study, it was succinylated to generate its water-soluble form, rutin succinate (RS), which was analyzed comparatively regarding the chemical structure and characteristic features of rutin. Biological activities of rutin and RS were compared on hemostatic parameters, and against toxic activities of crude BjV in vitro. In vivo, C57BL/6 mice were injected i.p. with either BjV alone or pre-incubated with rutin, RS or 1,10-phenanthroline (o-phe, an SVMP inhibitor), and the survival rates and hemostatic parameters were analyzed 48 h after envenomation. RS showed the characteristic activities described for rutin - i.e., antioxidant and inhibitor of protein disulfide isomerase - but also prolonged the clotting time of fibrinogen and plasma in vitro. Differently from rutin, RS inhibited typical proteolytic activities of SVMP, as well as the coagulant activity of BjV. Importantly, both rutin and RS completely abrogated the lethal activity of BjV, in the same degree as o-phe. BjV induced hemorrhages, falls in RBC counts, thrombocytopenia and hypofibrinogenemia in mice. Rutin and RS also improved the recovery of platelet counts and fibrinogen levels, and the development of hemorrhages was totally blocked in mice injected with BjV incubated with RS. In conclusion, RS has anticoagulant properties and is a novel SVMP inhibitor. Rutin and RS showed different mechanisms of action on hemostasis. Only RS inhibited directly BjV biological activities, even though both flavonoids neutralized B. jararaca toxicity in vivo. Our results showed clearly that rutin and RS show a great potential to be used as therapeutic compounds for snakebite envenomation.

In vitro and in vivo anti-inflammatory and anticoagulant activities of Myrciaria plinioides D. Legrand ethanol leaf extract

Myrciaria plinioides D. Legrand (Myrtaceae) is a native plant of Southern Brazil, which have potential in the food industry due to its edible fruits. Many plants belonging to this genus have been used for a variety of illnesses, including inflammatory disorders due to antioxidant properties. However, therapeutic uses of M. plinioides have been poorly studied. The aim of study was to assess the anti-inflammatory and anticoagulant activities of the ethanol leaf extract of M. plinioides. In M. plinioides extract-treated RAW 264.7 cells, assessments of cell viability, TNF-α release and p38 MAPK pathway-dependent protein expression were detected. In addition, rat paw edema models were used to analyze the anti-inflammatory effect of the extract. Macrophages cell line treated with M. plinioides extract showed a slight decrease in cell viability. In LPS-stimulated macrophages treated with different concentrations of the extract for 24 h, TNF-α release was inhibited, while modulation of p38 signaling pathway and inhibition of NF-κB p65 protein expression were dose-dependent. In rats, the extract inhibited the formation of paw edema, while an inhibitory effect on trypsin-like enzymes derived from mast cells was seen. Furthermore, the extract presented anticoagulant activity via extrinsic pathway, being able to block specifically factor Xa and thrombin. The study suggests that extract possess potent anti-inflammatory and anticoagulant effects. M. plinioides present great biological potential as a source for the development of anti-inflammatory and anticoagulant drugs. Additional studies can be proposed to better elucidate the mechanism by which M. plinioides exerts its effects.

Structural characterization of anticoagulant and antithrombotic polysaccharides isolated from Caesalpinia ferrea stem barks

This study aimed to isolate, characterize chemical-structurally and evaluate the effects of polysaccharides from Caesalpinia (Libidibia) ferrea stem barks in the haemostatic system. The deproteinated-polysaccharide extract (PE-Cf) after being fractionated by ion exchange chromatography-DEAE-cellulose resulted in three fractions (FI, FII, FIII) containing total carbohydrates (14.3-38%), including uronic acid (5-16%), and polyphenols (0.94-1.7 mg/g GAE). The polysaccharide fractions presented polydisperse profile in polyacrylamide gel electrophoresis (detected by Stains-All) and molecular masses (9.5 × 10⁴ Da-1.5 × 10⁵ Da) identified by gel permeation chromatography. FT-IR showed absorption bands (1630 cm^-1, 1396-1331 cm^-1), indicative of uronic acid, and a band at 1071 cm^-1, typical of COO^- groups of galacturonic acid. The NMR spectra of C. ferrea polysaccharides revealed a central core composed mainly by 5-linked α-Araf and minority components as α-Rhap and α-GalAp. UV spectra of fractions revealed discrete shoulders at 269-275 nm, characteristic of polyphenolic compounds. In vitro, polysaccharides inhibited the intrinsic and/or common coagulation pathway (aPTT test) (2.0-3.7 fold) and the platelet aggregation induced by 3 μM adenosine diphosphate (25-48%) and 5 μg/mL collagen (24%), but not that induced by arachidonic acid. In vivo, the polysaccharides inhibited (36-69%) venous thrombosis induced by hypercoagulability and stasis, showing discrete hemorrhagic effect. In conclusion, the polysaccharides of C. ferrea barks, containing arabinose, galactose, rhamnose and uronic acid, possess anticoagulant, antiplatelet and antithrombotic properties of low hemorrhagic risk, suggesting potential applicability in thromboembolic disorders.

Impact of epicatechin on fibrin clot structure

Fibrin clot structure and function are major determinants of thromboembolic diseases. The study aim was to determine the impact of epicatechin (a flavonoid with cardiovascular protective effects) on fibrin clot structure and permeability. Plasma samples from 12 healthy subjects were incubated with increasing concentrations of epicatechin. Turbidity of fibrin clot was analyzed by absorbance measurement at 405 nm. The fibrin clot nanostructure was determined by scanning spectrometry (wavelength from 500 to 800 nm) and fibrin fiber size by electron microscopy. Permeability was analyzed to assess the fibrin clot functional properties. Epicatechin addition increased the maximum absorbance from 0.34 ± 0.066 (vehicle) to 0.35 ± 0.077 (P = 0.1), 0.35 ± 0.072 (P < 0.05) and 0.34 ± 0.065 (P = 0.5) for 1, 10 and 100 μM epicatechin, respectively. Epicatechin increased the fibrin clot fiber radius (nm) from 109.2 ± 3.2 (vehicle) to 108.9 ± 4.3 (P = 0.9), 110.0 ± 3.6 (P < 0.05) and 109.5 ± 3.3 (P = 0.4), and the distance between protofibrils (nm) from 22.2 ± 1.5 (vehicle) to 22.1 ± 2.3 (P = 0.9), 22.6 ± 1.8 (P < 0.05) and 22.3 ± 1.8 (P = 0.9) for 1, 10 and 100 μM epicatechin respectively. Electron microscopy confirmed these changes. Fibrin clot permeability, expressed as Darcy's constant (Ks, cm²), increased from 2.97 ± 1.17 (vehicle) to 3.36 ± 1.21 (P < 0.05), 3.81 ± 1.41 (P < 0.01) and 3.38 ± 1.33 (P = 0.9). Upon epicatechin addition, the fibrin clot structure became less dense and more permeable.

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.

Epicatechin influences primary hemostasis, coagulation and fibrinolysis

The different stages of hemostasis (i.e., primary hemostasis, coagulation and fibrinolysis) are involved in the early atherothrombosis steps. The aim of this study was to investigate the effect of epicatechin, a major flavonoid compound, on the hemostasis phenotype using clinically relevant in vitro global assays that mimic the complexity of the in vivo hemostasis systems. Plasma samples from 10 healthy volunteers were spiked with increasing concentrations of epicatechin (1 to 100 μM). Epicatechin effect on primary hemostasis, coagulation and fibrinolysis was assessed by measuring platelet aggregation using light transmission aggregometry, thrombin generation and clot lysis time (CLT), respectively. Epicatechin (100 μM) significantly decreased the maximal platelet aggregation induced by adenosine diphosphate (-39%), thrombin receptor activating peptide (-48%), epinephrine (-30%), and collagen (-30%). The endogenous thrombin potential was significantly reduced starting from 1 μM epicatechin (1332 ± 230 versus 1548 ± 241 nM min for control) (p < 0.01). Fibrinolysis was promoted by epicatechin, as indicated by CLT decrease by 16 and 33% with 10 and 100 μM epicatechin respectively, compared with control (1271 ± 775 s). These findings show that epicatechin reduces platelet function and leads to an anticoagulant and pro-fibrinolytic profile, providing new evidence of its interest for cardiovascular disease prevention.

Critical pharmacokinetic and pharmacodynamic drug-herb interactions in rats between warfarin and pomegranate peel or guava leaves extracts

BACKGROUND

In-depth information of potential drug-herb interactions between warfarin and herbal compounds with suspected anticoagulant blood thinning effects is needed to raise caution of concomitant administration. The current study aimed to investigate the impact of co-administration of pomegranate peel and guava leaves extracts, including their quality markers namely; ellagic acid and quercetin, respectively, on warfarin's in vivo dynamic activity and pharmacokinetic actions, in addition to potential in vitro cytochrome P450 enzymes (CYP) inhibition.

METHODS

Influence of mentioned extracts and their key constituents on warfarin pharmacodynamic and kinetic actions and CYP activity were evaluated. The pharmacodynamic interactions were studied in Sprague Dawley rats through prothrombin time (PT) and International Normalized Ratio (INR) measurements, while pharmacokinetic interactions were detected in vivo using a validated HPLC method. Furthermore, potential involvement in CYP inhibition was also investigated in vitro on isolated primary rat hepatocytes.

RESULTS

Preparations of pomegranate peel guava leaf extract, ellagic acid and quercetin in combination with warfarin were found to exert further significant increase on PT and INR values (p < 0.01) than when used alone (p < 0.05). Pomegranate peel extract showed insignificant effects on warfarin pharmacokinetics (p > 0.05), however, its constituent, namely, ellagic acid significantly increased warfarin Cmax (p < 0.05). Guava leaves extract and quercetin resulted in significant increase in warfarin Cmax when compared to control (p < 0.01). Furthermore, guava leaves extract showed a significant effect on changing the AUC, CL and Vz. Significant reduction in CYP2C8, 2C9, and 3A4 was seen upon concomitant use of warfarin with ellagic acid, guava leaves and quercetin, unlike pomegranate that insignificantly affected CYP activities.

CONCLUSION

All combinations enhanced the anticoagulant activity of warfarin as the results of in vivo and in vitro studies were consistent. The current investigation confirmed serious drug herb interactions between warfarin and pomegranate peel or guava leaf extracts. Such results might conclude a high risk of bleeding from the co-administration of the investigated herbal drugs with warfarin therapy. In addition, the results raise attention to the blood-thinning effects of pomegranate peel and guava leaves when used alone.

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.

Marine Diterpenes: Molecular Modeling of Thrombin Inhibitors with Potential Biotechnological Application as an Antithrombotic

Thrombosis related diseases are among the main causes of death and incapacity in the world. Despite the existence of antithrombotic agents available for therapy, they still present adverse effects like hemorrhagic risks which justify the search for new options. Recently, pachydictyol A, isopachydictyol A, and dichotomanol, three diterpenes isolated from Brazilian marine brown alga Dictyota menstrualis were identified as potent antithrombotic molecules through inhibition of thrombin, a key enzyme of coagulation cascade and a platelet agonist. Due to the biotechnological potential of these marine metabolites, in this work we evaluated their binding mode to thrombin in silico and identified structural features related to the activity in order to characterize their molecular mechanism. According to our theoretical studies including structure-activity relationship and molecular docking analysis, the highest dipole moment, polar surface area, and lowest electronic density of dichotomanol are probably involved in its higher inhibition percentage towards thrombin catalytic activity compared to pachydictyol A and isopachydictyol A. Interestingly, the molecular docking studies also revealed a good shape complementarity of pachydictyol A and isopachydictyol A and interactions with important residues and regions (e.g., H57, S195, W215, G216, and loop-60), which probably justify their thrombin inhibitor effects demonstrated in vitro. Finally, this study explored the structural features and binding mode of these three diterpenes in thrombin which reinforced their potential to be further explored and may help in the design of new antithrombotic agents.

Interaction between wheat alpha-amylase/trypsin bi-functional inhibitor and mammalian digestive enzymes: Kinetic, equilibrium and structural characterization of binding

Alpha-amylase/trypsin bi-functional inhibitors (ATIs) are non-gluten protein components of wheat and other cereals that can hypersensitise the human gastrointestinal tract, eventually causing enteropathies in predisposed individuals. These inhibitory proteins can act both directly by targeting specific pro-inflammatory receptors, and indirectly by impairing the activity of digestive enzymes, the latter event causing the accumulation of undigested peptides with potential immunogenic properties. Herein, according to a concerted approach based on in vitro and in silico methods we characterized kinetics, equilibrium parameters and modes of binding of the complexes formed between wheat ATI and two representative mammalian digestive enzymes, namely trypsin and alpha-amylase. Interestingly, we demonstrated ATI to target both enzymes with independent binding sites and with moderately high affinity.

Mangiferin blocks proliferation and induces apoptosis of breast cancer cells via suppression of the mevalonate pathway and by proteasome inhibition

Mangiferin is a natural xanthone glycoside with therapeutic potential.

Investigation into the effects of antioxidant-rich extract of Tamarindus indica leaf on antioxidant enzyme activities, oxidative stress and gene expression profiles in HepG2 cells

The leaf extract of Tamarindus indica L. (T. indica) had been reported to possess high phenolic content and showed high antioxidant activities. In this study, the effects of the antioxidant-rich leaf extract of the T. indica on lipid peroxidation, antioxidant enzyme activities, H₂O₂-induced ROS production and gene expression patterns were investigated in liver HepG2 cells. Lipid peroxidation and ROS production were inhibited and the activity of antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase was enhanced when the cells were treated with the antioxidant-rich leaf extract. cDNA microarray analysis revealed that 207 genes were significantly regulated by at least 1.5-fold (p < 0.05) in cells treated with the antioxidant-rich leaf extract. The expression of KNG1, SERPINC1, SERPIND1, SERPINE1, FGG, FGA, MVK, DHCR24, CYP24A1, ALDH6A1, EPHX1 and LEAP2 were amongst the highly regulated. When the significantly regulated genes were analyzed using Ingenuity Pathway Analysis software, “Lipid Metabolism, Small Molecule Biochemistry, Hematological Disease” was the top biological network affected by the leaf extract, with a score of 36. The top predicted canonical pathway affected by the leaf extract was the coagulation system (P < 2.80 × 10⁻⁶) followed by the superpathway of cholesterol biosynthesis (P < 2.17 × 10⁻⁴), intrinsic prothrombin pathway (P < 2.92 × 10⁻⁴), Immune Protection/Antimicrobial Response (P < 2.28 × 10⁻³) and xenobiotic metabolism signaling (P < 2.41 × 10⁻³). The antioxidant-rich leaf extract of T. indica also altered the expression of proteins that are involved in the Coagulation System and the Intrinsic Prothrombin Activation Pathway (KNG1, SERPINE1, FGG), Superpathway of Cholesterol Biosynthesis (MVK), Immune protection/antimicrobial response (IFNGR1, LEAP2, ANXA3 and MX1) and Xenobiotic Metabolism Signaling (ALDH6A1, ADH6). In conclusion, the antioxidant-rich leaf extract of T. indica inhibited lipid peroxidation and ROS production, enhanced antioxidant enzyme activities and significantly regulated the expression of genes and proteins involved with consequential impact on the coagulation system, cholesterol biosynthesis, xenobiotic metabolism signaling and antimicrobial response.

Evaluation of Potential Thrombin Inhibitors from the White Mangrove (Laguncularia racemosa (L.) C.F. Gaertn.)

The aim of this work was to verify the effects of methanol (MeOH) and hydroalcoholic (HA) extracts and their respective partition phases obtained from white mangrove (Laguncularia racemosa (L.) C.F. Gaertn.) leaves on human thrombin activity. Among the extracts and phases tested, only the ethyl acetate and butanolic partitions significantly inhibited human thrombin activity and the coagulation of plasma in the presence of this enzyme. Chromatographic analyses of the thrombin samples incubated with these phases revealed that different compounds were able to interact with thrombin. The butanolic phase of the MeOH extract had the most potent inhibitory effects, reducing enzymatic activity and thrombin-induced plasma coagulation. Two glycosylated flavonoids in this partition were identified as the most potent inhibitors of human thrombin activity, namely quercetin-3-O-arabinoside (QAra) and quercetin-3-O-rhamnoside (Qn). Chromatographic analyses of thrombin samples incubated with these flavonoids demonstrated the chemical modification of this enzyme, suggesting that the MeOH extract contained other compounds that both induced structural changes in thrombin and diminished its activity. In this article, we show that despite the near absence of the medical use of mangrove compounds, this plant contains natural compounds with potential therapeutic applications.

Anticoagulant Activity of Polyphenolic-Polysaccharides Isolated from Melastoma malabathricum L

Melastoma malabathricum Linn. is a perennial traditional medicine plants that grows abundantly throughout Asian countries. In this study, M. malabathricum Linn. leaf hot water crude extract with anticoagulant activity was purified through solid phase extraction cartridge and examined for the bioactive chemical constituents on blood coagulation reaction. The SPE purified fractions were, respectively, designated as F1, F2, F3, and F4, and each was subjected to the activated partial thromboplastin time (APTT) anticoagulant assay. Active anticoagulant fractions (F1, F2, and F3) were subjected to chemical characterisation evaluation. Besides, neutral sugar for carbohydrate part was also examined. F1, F2, and F3 were found to significantly prolong the anticoagulant activities in the following order, F1 > F2 > F3, in a dose dependent manner. In addition, carbohydrate, hexuronic acid, and polyphenolic moiety were measured for the active anticoagulant fractions (F1, F2, and F3). The characterisation of chemical constituents revealed that all these three fractions contained acidic polysaccharides (rhamnogalacturonan, homogalacturonan, and rhamnose hexose-pectic type polysaccharide) and polyphenolics. Hence, it was concluded that the presence of high hexuronic acids and polysaccharides, as well as polyphenolics in traditional medicinal plant, M. malabathricum, played a role in prolonging blood clotting in the intrinsic pathway.

Polyphenol compounds belonging to flavonoids inhibit activity of coagulation factor X

Blood coagulation consists of series of zymogens which can be converted by limited proteolysis to active enzymes leading to the generation of thrombin and conversion of fibrinogen into fibrin by this enzyme. The activated factor X (FXa) forms prothrombinase complex on phosphatidylserine containing surface which is responsible for conversion of prothrombin to thrombin. One molecule of FXa generates more than 1000 thrombin molecules. Therefore FXa is a novel target for modern anticoagulant therapy. The aim of our present study is to examine the effects of the well-known plant polyphenolic compounds on factor Xa amidolytic activity and characterization of these interactions using bioinformatic ligand docking method. We observed that only four polyphenols belonging to flavonoids group: procyanidin B2, cyanidin, quercetin and silybin, had inhibitory effect on FXa activity. Bioinformatic analyses revealed that procyanidin B2, cyanidin, quercetin and silybin bound in the S1-S4 pockets located in vicinity of the FXa active site and blocked access of substrates to Ser195. The results presented here showed that flavonoids might be potential structural bases for design of new nature-based, safe, orally bioavailable direct FXa inhibitors.

Thrombin inhibitory activity of some polyphenolic compounds

Thrombin, also known as an active plasma coagulation factor II, belongs to the family of serine proteases and plays a crucial role in blood coagulation process. The process of thrombin generation is the central event of the hemostatic process and regulates blood coagulant activity. For this reason, thrombin inhibition is key to successful novel antithrombotic pharmacotherapy. The aim of our present study was to examine the effects of the well-known polyphenolic compounds on the activity of thrombin, by characterization of its interaction with selected polyphenols using different biochemical methods and biosensor BIAcore analyses. Only six compounds, cyanidin, quercetin, silybin, cyanin, (+)-catechin and (-)-epicatechin, of all examined in this study polyphenols caused the inhibition of thrombin amidolytic activity. But only three of the six compounds (cyanidin, quercetin and silybin) changed thrombin proteolytic activity. BIAcore analyses demonstrated that cyanidin and quercetin caused a strong response in the interaction with immobilized thrombin, while cyanin and (-)-epicatechin induced a low response. Lineweaver-Burk curves show that used polyphenol aglycones act as competitive thrombin inhibitors. Our results suggest that polyphenolic compounds might be potential structural bases and source to find and project nature-based, safe, orally bioavailable direct thrombin inhibitors.

Antithrombin effect of polyphenol-rich extracts from black chokeberry and grape seeds

Thrombin is a serine protease that cleaves the peptide bonds in proteins located on the carboxyl side of arginine. Thrombin plays a central role in thromboembolic diseases, which are the major cause of mortality. The aim of the study was to estimate the effects of plant extracts on proteolytic properties of thrombin. Thrombin was incubated with polyphenol-rich extracts from berries of Aronia melanocarpa or seeds of Vitis vinifera (0.5, 5, 50 µg/mL) and with polyphenols ((+)-catechin, (-)-epicatechin, gallic acid, chlorogenic acid, procyanidin B1, cyanidin, cyanidin 3-glucoside, quercetin). The in vitro experiments showed that both extracts in all used concentrations inhibited proteolytic activity of thrombin observed as inhibition of thrombin-induced fibrinogen polymerization, stabilized fibrin formation, and platelet aggregation. Moreover, thrombin amidolytic activity was inhibited by polyphenols belonging to the flavonoid class. Results presented in this study indicate that polyphenol-rich extracts from berries of A. melanocarpa and seeds of V. vinifera may become promising dietary supplements in the prevention of thrombotic states.

Sanguisorba minor extract suppresses plasmin-mediated mechanisms of cancer cell migration

BACKGROUND

Sanguisorba minor, as well as several other edible herbs and vegetables, has been used extensively in traditional medicine. The observed beneficial effects can be attributed at least in part to the direct modulation of several enzymatic activities by its polyphenolic constituents.

METHODS

The ethanol extract of Sanguisorba minor was characterized by reversed-phase liquid chromatography, and most relevant analytes were identified by multiple stage mass spectrometry. The whole extract and the most relevant isolated constituents were tested for their ability to modulate the activity of human plasmin both toward a synthetic substrate and in human breast cancer cell culture models. Kinetic and equilibrium parameters were obtained by a concerted spectrophotometric and biosensor-based approach.

RESULTS

Quercetin-3-glucuronide was recognized as the compound mainly responsible for the in vitro plasmin inhibition by S. minor extract, with an inhibition constant in the high nanomolar range; in detail, our approach based on bioinformatic, enzymatic and binding analyses classified the inhibition as competitive. Most interestingly, cell-based assays showed that this flavonoid was effective in suppressing plasmin-induced loss of cancer cell adhesion.

GENERAL SIGNIFICANCE

Our results show that the extract from Sanguisorba minor limits plasmin-mediated tumor cell motility in vitro, mostly due to quercetin-3-glucuronide. This glucuronated flavonoid is a promising template for rational designing of anticancer drugs to be used in the treatment of pathological states involving the unregulated activity of plasmin.

Polyphenol fatty acid esters as serine protease inhibitors: a quantum-chemical QSAR analysis

We investigated the ability of polyphenol fatty acid esters to inhibit the activity of serine proteases trypsin, thrombin, elastase and urokinase. Potent protease inhibition in micromolar range was displayed by rutin and rutin derivatives esterified with medium and long chain, mono- and polyunsaturated fatty acids (1e-m), followed by phloridzin and esculin esters with medium and long fatty acid chain length (2a-d, 3a-d), while unmodified compounds showed only little or no effect. QSAR study of the compounds tested provided the most significant parameters for individual inhibition activities, i.e. number of hydrogen bond donors for urokinase, molecular volume for thrombin, and solvation energy for elastase. According to the statistical analysis, the action of elastase inhibitors is opposed to those of urokinase and thrombin. Cluster analysis showed two groups of compounds: original polyphenols together with rutin esters with short fatty acid chain length and rutin esters with long fatty acid chain length.

The polyphenol-rich extract from grape seeds inhibits platelet signaling pathways triggered by both proteolytic and non-proteolytic agonists

Mechanisms involved in the reduction of blood platelet functions by various plant extract, including the grape seeds extract (rich in phenolic compounds, a mixture of about 95% oligomeric phenols; GSE) are still unclear. In the literature there are few papers describing studies on the effects of GSE on selected element of hemostasis. The aim of our study was to establish and compare the influence of GSE (at final dose of 0.625-50 µg/ml) and resveratrol (3,4',5 - trihydroxystilben), a phenolic compound synthesized in grapes and vegetables and presents in wine, which has been supposed to be beneficial for the prevention of cardiovascular events, on different steps of platelet activation. We measured the effects of GSE and resveratrol on platelet aggregation, the surface expression of P-selectin, platelet microparticle formation (PMP), and superoxide anion radicals ([Formula: see text]) production in blood platelets stimulated by TRAP and thrombin. P-selectin expression and PMP formation were measured by a flow cytometer. In gel-filtered platelets activated by thrombin or TRAP and treated with different concentrations of GSE (1.25-50 µg/ml) a significant decrease of P-selectin expression, PMP formation and platelet aggregation was observed. GSE caused also a dose-dependent reduction of [Formula: see text] produced in platelets activated by TRAP or thrombin. Our present results indicate that GSE inhibits platelet signaling pathways trigged by both proteolytic (thrombin) and non-proteolytic agonist (TRAP). In the comparative studies, GSE was found to be more effective antiplatelet factor, than the solution of pure resveratrol. Thus, the polyphenol-rich extract from grape seeds can be useful as the protecting factor against cardiovascular diseases.

Anticoagulant effect of polyphenols-rich extracts from black chokeberry and grape seeds

Blood coagulation consists of a series of zymogens that can be converted by limited proteolysis to active enzymes leading to the generation of thrombin. Fresh plasma and human thrombin was incubated with extracts from berries of Aronia melanocarpa or seeds of Vitis vinifera (0.5; 5; 50 μg/ml). The in vitro experiments showed that both extracts prolonged clotting time and decreased the maximal velocity of fibrin polymerization in human plasma. Moreover thrombin incubation with both extracts results in the inhibition of amidolytic activity of this enzyme. It gives hopes for development of diet supplements, which may be preventing thrombosis in pathological states.

Natural occurring polyphenols as template for drug design. Focus on serine proteases

Several major physio-pathological processes, including cancer, inflammatory states and thrombosis, are all strongly dependent upon the fine regulation of proteolytic enzyme activities, and dramatic are the consequences of unbalanced equilibria between enzymes and their cognate inhibitors. In this perspective, the discovery of small-molecule ligands able to modulate catalytic activities has a massive therapeutic potential and is a stimulating goal. Numerous recent experimental evidences revealed that proteolytic enzymes can be opportunely targeted, reporting on small ligands capable of binding to these biological macromolecules with drug-like potencies, and primarily with comparable (or even higher) efficiency with respect to their endogenous binding partner. In particular, natural occurring polyphenols and their derivatives recently disclosed these intriguing abilities, making them promising templates for drug design and development. In this review, we compared the inhibitory capacities of a set of monomeric polyphenols toward serine proteases activity, and finally summarized the data with an emphasis on the derivation of a pharmacophore model.

Aflatoxin B1 misregulates the activity of serine proteases: possible implications in the toxicity of some mycotoxin

Aflatoxins are highly hazardous contaminants of common food and feed. Aflatoxin B1 in particular, the most predominant among aflatoxins, was thoroughly demonstrated to be highly toxic, mutagenic, teratogenic and carcinogenic in many animal species. Besides its established targets and effects, this work investigates on the possible direct interaction between aflatoxin B1 and three major serine proteases, namely elastase, thrombin and trypsin. These proteases belongs to a class of structurally and functionally related proteins pivotal in both direct and indirect regulation of a number of cellular events. Additionally, several pathological processes, including cancer, inflammatory processes and thrombosis, rely upon the subtle equilibrium between these enzymes and their potential modulators: in fact, their misregulation, caused by foreign molecules, could facilitate (or be the cause for) the occurrence of these pathologies. Our results provide the evidence for a reversible binding between AFB1 and these enzymes, likely to have profound implications in the manifestation of aflatoxicosis. Precisely, the toxin behaved as a moderate competitive inhibitor toward the enzymatic activity of the serine proteases in the low micromolar range.

Homology modeling and docking analysis of the interaction between polyphenols and mammalian 20S proteasomes

Molecular docking of small ligands to biologically active macromolecules has become a valuable strategy to predict the stability of complexes between potential partners and their binding modes. In this perspective, we applied this computational procedure to rationalize the reported role of polyphenols as inhibitors of the mammalian 20S proteasomes. In particular, polyphenols were shown to modulate each proteasomal activity at different extents both in the constitutive and the inducible enzyme. We performed a flexible molecular docking analysis between a set of polyphenols previously demonstrated to have the highest binding affinity and both the constitutive (from deposited PDB structures) and homology modeled active subunits of the IFN-gamma inducible proteasome, to provide insight into the possible mechanism of interaction. Among the tested polyphenols, (-)-epigallocatechin-3-gallate showed the highest affinity for the proteasome subunits, both in terms of intermolecular energy and predicted equilibrium constants, in particular for beta5 and beta5i subunits (E(total) = -66 kcal/mol, Ki = 81.3 microM and E(Total) = -83.9 kcal/mol, Ki = 0.29 microM, respectively), known to be related to the chymotrypsin-like and BrAAP activities. Collectively, polyphenols showed a higher affinity for the inducible subunits, in agreement with previous in vitro studies. Additionally, different contributions to the interaction energy (van der Waals, electrostatic, H-bond) of proteasome-polyphenols complexes were dissected.

Influence of aromatic and aliphatic moieties on thrombin inhibitors potency

Thrombin is a plasma serine protease that plays a key role in coagulation and hemostasis but also in thromboembolic diseases. Direct thrombin inhibitors could be beneficial for future anticoagulant therapy in the prophylaxis of venous and arterial thrombosis as well as myocardial infarction. To design the efficient thrombin inhibitors we have synthesized and studied peptide-based inhibitors resistant to enzymatic degradation. Compounds with general formula X-DArg-D-Phe-OMe, where X = residue of 3-[6-ethyl-7-hydroxy-3-(4-methyl-thiazol-2-yl)-4-oxo-4H-chromen-2-yl]-propionic acid (chromone) and lauric acid were synthesized by classic methods of peptides synthesis in solution. The comparative inhibitory analysis of prepared compounds in relation to thrombin was conducted. The analysis of the inhibition effect of the peptide with retro-D-sequence modified by residues of natural organic compounds (chromone or fatty acid moiety) has demonstrated that modification with the fatty acid residue appeared to be the most successful one. Introduction of lauric acid residue (Ki = 1,76 muM) maximally increased the inhibition effect. These findings establish an important role of fatty moiety in structure of inhibitors in preferential binding and inhibition of thrombin active side.

Mechanism of inhibition of wt-dihydrofolate reductase from E. coli by tea epigallocatechin-gallate

Dihydrofolate reductase (DHFR) is a ubiquitous enzyme involved in major biological process, including DNA synthesis and cancer inhibition, and its modulation is the object of extensive structural, kinetic, and pharmacological studies. In particular, earlier studies showed that green tea catechins are powerful inhibitors of bovine liver and chicken liver DHFR. In this article, we report the results of inhibition kinetics for the enzyme from another source (DHFR from E. coli) exerted by (-)-epigallocatechingallate (EGCG). Using different analytical techniques, we reported that EGCG acts as a bisubstrate inhibitor on the bacterial DHFR. Moreover, the combined approach of biosensor, kinetic, and molecular modelling analysis disclosed the ability of EGCG to bind to the enzyme both on substrate (DHF) and cofactor (NADPH) site. Collectively, our data have confirmed the selectivity of antifolate compounds with respect to the different source of enzyme (bacterial or mammalian DHFR) and the possible role of tea catechins as chemopreventive agents.

Antiplasmin activity of natural occurring polyphenols

The equilibrium between proteolytic enzymes and their cognate inhibitors is crucial in a number of physiological as well as pathological processes, including cancer, inflammatory processes and thrombosis. Therefore, both synthetic and natural small molecule inhibitors are object of extensive studies as drugs in the treatment of these pathologies. Two natural occurring polyphenolic compounds, representative of glycosylated and unglycosylated flavonoid structures, namely quercetin and rutin, were thereby tested as potential ligands of plasmin(ogen), a serine (pro)protease, whose role in tumor cell invasion and migration has been reported. Quercetin showed a ten folds higher affinity with plasmin with respect to rutin in terms of equilibrium dissociation constant, both compounds acting as in vitro moderate reversible inhibitors; additionally, quercetin and rutin prevented plasmin-incubated BB1 cells from releasing E-cadherin fragment to a different extent, respectively. Furthermore, a feasible mechanism of interaction was analyzed and discussed using a molecular modeling approach.