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

Potential for application of direct thrombin inhibitors isolated from Euphorbia resinifera O.Berg latex in fibrin clot formation

Direct thrombin inhibitors (designated as EuRL-DTIs) were partially purified from ethanol extracts of Euphorbia resinifera O.Berg latex. The obtained EuRL-DTIs comprised four major compounds: two isomers of phenolic compounds (C19H26O12) and two amide compounds (tentatively identified as C24H44N4O4 and C36H66N6O6), as identified by liquid chromatography and electrospray ionisation quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS/MS), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and/or nuclear magnetic resonance (NMR) spectroscopy. The effects of EuRL-DTIs on human thrombin-induced fibrin clot production were analysed using thrombin time, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), synchrotron radiation X-ray tomographic microscopy (SRXTM), and scanning electron microscopy (SEM). Kinetic studies revealed that EuRL-DTIs inhibited human thrombin from cleaving the chromogenic substrate S2238, with a Ki of 3.7 μg/mL, in a non-competitive inhibition manner. All results supported the hypothesis that the EuRL-DTIs directly abolished thrombin activity in the production of fibrin clots without requiring a cofactor. The cytotoxicity test showed that EuRL-DTIs were nontoxic to normal human foetal lung fibroblasts (IMR-90). Thus, EuRL-DTIs have potential as antithrombotic agents for application as drugs for thrombosis treatments or in medical devices such as coating surgical sutures.

Winery By-Products In Vitro and In Vivo Effects on Atherothrombotic Markers: Focus on Platelet-Activating Factor

Platelet aggregation and inflammation play a crucial role in atherothrombosis. Wine contains micro-constituents of proper quality and quantity that exert cardioprotective actions, partly through inhibiting platelet-activating factor (PAF), a potent inflammatory and thrombotic lipid mediator. However, wine cannot be consumed extensively due to the presence of ethanol. Alternatively, winery by-products are abundant in similar-to-wine micro-constituents that could be used in food fortification and dietary supplements. Also, the vinification process produces millions of tons of by-products worldwide, posing an environmental matter of waste management. Therefore, the purpose of this literature review is to update the existing data concerning the in vitro anti-platelet and anti-inflammatory properties of winery by-product extracts and their possible health effects through controlled clinical trials in humans, specifically focused on their effects on PAF's actions. Data from in vitro studies report that winery by-product compounds are able to inhibit platelet aggregation against several aggregation factors, as well as to downregulate inflammatory markers. Among their actions, extracts or phenolic compounds present in winery by-products inhibit PAF's actions, a potent inflammatory and thrombotic mediator. Similar conclusions have been drawn from human supplementation studies, which suggest that winery by-product extracts may have beneficial biological effects on the cardiovascular system. Evidence from long-term studies shows that consumption may lower total and low density lipoprotein (LDL) cholesterol, improve insulin sensitivity, decrease lipid and protein oxidative damage, enhance antioxidant capacity, and have mild anti-inflammatory action toward reducing cytokine expression and levels. Data from the limited postprandial studies report that the acute consumption of winery by-product extracts improves glycemic response and reduces platelet reactivity to aggregatory stimuli. Although wine extracts and phenolic compounds have been reported to inhibit PAF's actions and reduce the activity of its biosynthetic enzymes, no data exist concerning the influence of winery by-product extracts. In the future, additional long-term randomized controlled trials or postprandial studies are needed to draw definitive conclusions and establish a viable cardioprotective strategy that incorporates the sustainable use of winery by-products.

The Effects of Sorbus aucuparia L. Fruit Extracts on Oxidative/Nitrative Modifications of Human Fibrinogen, Impact on Enzymatic Properties of Thrombin, and Hyaluronidase Activity In Vitro

Sorbus aucuparia L. fruits (rowanberries) are food products with acknowledged nutritional value, high phenolic content, and traditional application in diabetes. In this study, the effects of rowanberry extracts (phytochemically standardised, i.a., by LC-MS/MS) on some aspects of plasma haemostasis and vascular conditions were evaluated in vitro as possible mechanisms connected with cardiovascular complications of diabetes. The analyses of structural modifications of human fibrinogen under oxidative stress conditions (C-ELISA, SDS-PAGE and Western blot) revealed that the extracts (at a concentration of 1-5 µg/mL) considerably reduced the nitration of tyrosine residues and formation of high-molecular-weight aggregates. Moreover, they inhibited the enzymatic activity of thrombin (both amidolytic and proteolytic). Additionally, some promising outcomes might be expected regarding endothelial functions from the extracts ability to inhibit hyaluronidase. Parallel experiments on model polyphenols and correlation studies formed the basis for determining the contribution of different compounds, including hydroxycinnamic acid derivatives, flavonols, and low- or high-molecular-weight flavan-3-ols derivatives (proanthocyanidins), to the observed effects. The possible synergistic activity of individual constituents was also noticed. These results broaden the knowledge on the biological activity of rowanberries, partly confirming their health-promoting properties, and indicating that their functional applications might be promising.

Thermally driven formation of polyphenolic carbonized nanogels with high anticoagulant activity from polysaccharides

We have demonstrated that alginate with negligible anticoagulant activity can be converted into carbonized nanogels with potent anticoagulant activity through a solid-state heating process. The conversion of alginate into graphene-like nanosheet (GNS)-embedded polyphenolic-alginate nanogels (GNS/Alg-NGs) has been carried out through condensation and carbonization processes. The GNS/Alg-NGs exhibit much stronger anticoagulant activity (>520-fold) compared to untreated alginate, mainly because their polyphenolic structures have a high binding affinity [dissociation constant (K_d) = 2.1 × 10^-10 M] toward thrombin. In addition, the thrombin clotting time delay caused by the GNS/Alg-NGs is 10-fold longer than that of natural polyphenolic compounds, such as quercetin, catechin, naringenin, caffeic acid, and ferulic acid. The thrombin- or kaolin-activated thromboelastography of whole-blood coagulation reveals that the GNS/Alg-NGs display a much stronger anticoagulant ability than that of untreated alginate and naturally sulfated polysaccharides (fucoidan). The GNS/Alg-NGs exhibit superior biocompatibility and anticoagulant activity, as observed with an in vivo rat model, revealing their potential as a blood thinner for the treatment of thrombotic disorders.

Evaluation of anti-platelet activity of grape pomace extracts

Platelets aggregation plays a crucial role in atherothrombosis. Therefore, the aim of the present study was to examine the anti-platelet activity of winery by-products extracts, to find the most potent one and to be further analyzed in order to be used for food fortification. For this purpose, grape pomace from four red varieties was extracted with four solvents of different polarity. The extracts' phenolic content, antioxidant capacity and their ability to inhibit human platelet aggregation against PAF, ADP, TRAP were determined by Light Transmission Aggregometry. The ethanolic extract was further analyzed concerning its anti-platelet effect and its chemical composition by LC-MS/MS and GC-MS. The ethanolic and Bligh-Dyer water phase extracts showed the highest phenolic compounds/anthocyanin content and the best antioxidant activity. However, the most potent inhibition of platelet aggregation was revealed by ethanol extracts, followed by the Bligh-Dyer lipoid phase extracts. Ethanolic extract, found to contain micro-constituents such as phospho-compounds, phenolic compounds and fatty acids. The most abundant phenolic compounds were catechin, epicatechin and quercetin and the most abundant fatty acids were linoleic acid (C18:2n6), linolenic acid (C18:3n3) and palmitic acid (C16:0). Ethanolic extract was capable of inhibiting platelets aggregation in a wide range of agonist concentrations and it also seems that its action is sustained when platelets from coronary heart disease patient were used. Ethanol extract of winery by-products exerts a potent anti-platelet effect and its valorization could lead to the production of functional foods with cardioprotective properties.

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.

Dual Anticoagulant/Antiplatelet Activity of Polyphenolic Grape Seeds Extract

Because of the side-effects of commonly used anti-platelet and anticoagulant drugs, investigations into plant substances with similar activities are very common. Based on our own studies in recent years, we estimate that it is possible to use natural compounds to both inhibit coagulation pathway enzymes and to reduce blood platelets’ activation. As such, in our current study we wanted to verify the anti-platelet and anticoagulant properties of grape seed extract (GSE) using in vitro models. During our analysis, the following parameters were analyzed: Coagulation times, thromboelastometry assays (coagulation time, clot formation time and maximum clot firmness), aggregation of platelets and phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Adenosine diphosphate (ADP)-induced aggregation was lower in GSE 7.5 µg/mL as well as in GSE 15.0 µg/mL. A similar dependence was observed in VASP assays for GSE 7.5 µg/mL and GSE 15 µg/mL. The effect on plasma coagulation tests was distinct only with GSE 15 µg/mL. All of the thromboelastometry variables were statistically significant with 15.0 µg/mL GSE concentration. Our results show, for the first time, the multi-potential effect of grape seed extract on coagulation systems, and clearly suggest that grape seed extract could be considered a promising nutraceutical in the prevention of cardiovascular thrombotic events caused by different mechanisms.

Phenolic fractions from nine Trifolium species modulate the coagulant properties of blood plasma in vitro without cytotoxicity towards blood cells

OBJECTIVE

The study covers an evaluation of the influence of extracts (1-50 μg/ml), isolated from aerial parts of nine Trifolium L. species (i.e. T. alexandrinum, T. fragiferum, T. hybridum, T. incarnatum, T. pallidum, T. pratense, T. resupinatum var. majus, T. resupinatum var. resupinatum and T. scabrum) on haemostatic properties of blood plasma.

METHODS

The clot formation and fibrinolysis assay (CFF), blood clotting times, the extrinsic and intrinsic coagulation pathway-dependent polymerization of plasma fibrin were measured. The effects of plant extracts on amidolytic activity of thrombin were also evaluated and compared with argatroban, an antithrombotic drug. Cytotoxicity was assessed in a model of blood platelets and as the viability of peripheral blood mononuclear cells.

KEY FINDINGS

While no changes in blood clotting times or fibrinolytic properties of blood plasma were found, some fractions impaired the blood plasma coagulation induced by the intrinsic coagulation pathway. Reduction in the maximal velocity of fibrin polymerization was also observed in the clot formation and fibrinolysis assay. No cytotoxicity of Trifolium extracts towards the investigated cells was recorded.

CONCLUSIONS

The most efficient anticoagulant activity in plasma was found for T. fragiferum and T. incarnatum extracts, while the T. alexandrinum fraction was the most effective inhibitor of thrombin amidolytic activity.

Haplotype analysis of the germacrene A synthase gene and association with cynaropicrin content and biological activities in Cynara cardunculus

Cynara cardunculus: L. represents a natural source of terpenic compounds, with the predominant molecule being cynaropicrin. Cynaropicrin is gaining interest since it has been correlated to anti-hyperlipidaemia, antispasmodic and cytotoxicity activity against leukocyte cancer cells. The objective of this work was to screen a collection of C. cardunculus, from different origins, for new allelic variants in germacrene A synthase (GAS) gene involved in the cynaropicrin biosynthesis and correlate them with improved cynaropicrin content and biological activities. Using high-resolution melting, nine haplotypes were identified. The putative impact of the identified allelic variants in GAS protein was evaluated by bioinformatic tools and polymorphisms that putatively lead to protein conformational changes were described. Additionally, cynaropicrin and main pentacyclic triterpenes contents, and antithrombin, antimicrobial and antiproliferative activities were also determined in C. cardunculus leaf lipophilic-derived extracts. In this work we identified allelic variants with putative impact on GAS protein, which are significantly associated with cynaropicrin content and antiproliferative activity. The results obtained suggest that the identified polymorphisms should be explored as putative genetic markers correlated with biological properties in Cynara cardunculus.

Impact of novel SNPs identified in Cynara cardunculus genes on functionality of proteins regulating phenylpropanoid pathway and their association with biological activities

BACKGROUND

Cynara cardunculus L. offers a natural source of phenolic compounds with the predominant molecule being chlorogenic acid. Chlorogenic acid is gaining interest due to its involvement in various biological properties such as, antibacterial, antifungal, antioxidant, hepatoprotective, and anticarcinogenic activities.

RESULTS

In this work we screened a Cynara cardunculus collection for new allelic variants in key genes involved in the chlorogenic acid biosynthesis pathway. The target genes encode p-coumaroyl ester 3'-hydroxylase (C3'H) and hydroxycinnamoyl-CoA: quinate hydroxycinnamoyl transferase (HQT), both participating in the synthesis of chlorogenic acid. Using high-resolution melting, the C3'H gene proved to be highly conserved with only 4 haplotypes while, for HQT, 17 haplotypes were identified de novo. The putative influence of the identified polymorphisms in C3'H and HQT proteins was further evaluated using bioinformatics tools. We could identify some polymorphisms that may lead to protein conformational changes. Chlorogenic acid content, antioxidant and antithrombin activities were also evaluated in Cc leaf extracts and an association analysis was performed to assess a putative correlation between these traits and the identified polymorphisms.

CONCLUSION

In this work we identified allelic variants with putative impact on C3'H and HQT proteins which are significantly associated with chlorogenic acid content and antioxidant activity. Further study of these alleles should be explored to assess putative relevance as genetic markers correlating with Cynara cardunculus biological properties with further confirmation by functional analysis.

Investigation of the anticoagulant and antithrombotic effects of chlorogenic acid

Thrombosis is a leading cause of morbidity and mortality throughout the world. Thrombolytic agents are important for both the prevention and treatment of thrombosis. Fibrin clot and turbidity assays revealed that it was able to inhibit the formation of fibrin clot. Chlorogenic acid degraded blood clot and inhibited the enzymatic activity of procoagulant proteases, thrombin, activated factor X (FXa), and activated factor XIII (FXIIIa). Chlorogenic acid was found to delay activated partial thromboplastin time, prothrombin time, and thrombin time. PFA-100 assays showed that it prolonged the closure time of citrated whole human blood. It demonstrated the antithrombotic effect in collagen and epinephrine-induced acute thromboembolism mice model. These antithrombotic profiles together with its anticoagulant and platelet disaggregation properties, and lack of toxicity to NIH-3T3 and 3T3-L1 cells, make it a potential agent for thrombotic treatment and prevention.

Popular naturally occurring antioxidants as potential anticoagulant drugs

Blood coagulation is a physiological process whose main task is prevention of blood loss from injured vessels. This process consists of a series of zymogens proteolytic activation leading to the generation of the main coagulation enzyme - thrombin. Besides its important role in blood coagulation process, thrombin is involved in many cardiovascular diseases, which are responsible for almost half of fatalities in economically developed countries. The evidence for the increased generation and in vivo activity of thrombin was observed in the plasma of individuals at high risk for clinically significant venous and arterial thromboembolic complications. Antioxidants activity of plants extracts has been well known for many years and was confirmed by many publications. However, during the last decade many research centers presented results suggesting anticoagulant potential of various plant extracts. Many researchers have also provided evidence that polyphenol compounds are able to inhibit the activity of many enzymes, including serine proteases. All research described in this review clearly indicate that polyphenols and polyphenol-rich extracts possess not only antioxidative but also anticoagulant properties and may be useful in creation of new therapeutic agents or dietary supplements. Based on described properties polyphenols would be very helpful with both prevention and treatment of thromboembolic complications associated with multiple failures of haemostasis, because the available therapeutic agents do not offer such double-effects (antioxidant and anticoagulant).

A chemical family-based strategy for uncovering hidden bioactive molecules and multicomponent interactions in herbal medicines

Two concepts involving natural products were proposed and demonstrated in this paper. (1) Natural product libraries (e.g. herbal extract) are not perfect for bioactivity screening because of the vast complexity of compound compositions, and thus a library reconstruction procedure is necessary before screening. (2) The traditional mode of “screening single compound” could be improved to “screening single compound, drug combination and multicomponent interaction” due to the fact that herbal medicines work by integrative effects of multi-components rather than single effective constituents. Based on the two concepts, we established a novel strategy aiming to make screening easier and deeper. Using thrombin as the model enzyme, we firstly uncovered the minor lead compounds, potential drug combinations and multicomponent interactions in an herbal medicine of Dan-Qi pair, showing a significant advantage over previous methods. This strategy was expected to be a new and promising mode for investigation of herbal medicines.

Antioxidant and protease-inhibitory potential of extracts from grains of oat

The most of important crops cultivated for production of foods and feeds could be considered as plants possessing nutraceutical or medically interesting compounds, especially if can be eaten without processing. Chemical and biological parameters that were evaluated in 100 oat (Avena sativa L.) genotypes were others than those that are important in food and feed production. Contents of polyphenols and flavonoids, radical scavenging activity (DPPH), and inhibitory activities against five proteases (trypsin, thrombin, urokinase, elastase, cathepsin B) were analyzed in extracts from mature grains. The antioxidant activity (DPPH) correlated to the content of total polyphenols. Only a minority (15 from 100) of analyzed genotypes created separate subgroup with a high content of polyphenols, flavonoids, and high antioxidant activity. The best in these parameters were genotypes CDC-SOL-FI, Saul, and Avesta, respectively. Fifteen other genotypes assembled another minority subgroup (also 15 from 100) on the basis of their high inhibitory activities against tested proteases. The highest trypsin-, urokinase-, and elastase-inhibitory activities were in genotype Racoon, the best in thrombin-, and cathepsin B-inhibitory activities were genotypes Expression and SW Kerstin, respectively. Three oats genotypes – Rhea, AC Percy, and Detvan appeared in both subgroups.

Screening of direct thrombin inhibitors from Radix Salviae Miltiorrhizae by a peak fractionation approach

Thrombin plays a significant role in thromboembolic disease. In this work, a peak fractionation approach combined with an activity assay method was used to screen direct thrombin inhibitors from Radix Salviae Miltiorrhizae (RSM), a famous herbal remedy for the treatment of cardiovascular diseases in China. A total of 91 fractions were collected from the RSM extract, and 19 fractions out of them showed thrombin inhibitory effects with dose-effect relationship. Among them, three compounds were unambiguously identified as 15, 16-dihydrotanshinone I, cryptotanshinone and tanshinone IIA with IC50 values of 29.39, 81.11 and 66.60μM, respectively. The three compounds were reported with direct thrombin inhibition activities for the first time and their ligand-thrombin interactions were explored by a molecular docking research. These results may contribute to explain the medical benefit of RSM for the prevention and treatment of cardiovascular diseases.

Effects of dark chocolate consumption on the prothrombotic response to acute psychosocial stress in healthy men

Flavanoid-rich dark chocolate consumption benefits cardiovascular health, but underlying mechanisms are elusive. We investigated the acute effect of dark chocolate on the reactivity of prothrombotic measures to psychosocial stress. Healthy men aged 20-50 years (mean ± SD: 35.7 ± 8.8) were assigned to a single serving of either 50 g of flavonoid-rich dark chocolate (n=31) or 50 g of optically identical flavonoid-free placebo chocolate (n=34). Two hours after chocolate consumption, both groups underwent an acute standardised psychosocial stress task combining public speaking and mental arithmetic. We determined plasma levels of four stress-responsive prothrombotic measures (i. e., fibrinogen, clotting factor VIII activity, von Willebrand Factor antigen, fibrin D-dimer) prior to chocolate consumption, immediately before and after stress, and at 10 minutes and 20 minutes after stress cessation. We also measured the flavonoid epicatechin, and the catecholamines epinephrine and norepinephrine in plasma. The dark chocolate group showed a significantly attenuated stress reactivity of the hypercoagulability marker D-dimer (F=3.87, p=0.017) relative to the placebo chocolate group. Moreover, the blunted D-dimer stress reactivity related to higher plasma levels of the flavonoid epicatechin assessed before stress (F=3.32, p = 0.031) but not to stress-induced changes in catecholamines (p's=0.35). There were no significant group differences in the other coagulation measures (p's≥0.87). Adjustments for covariates did not alter these findings. In conclusion, our findings indicate that a single consumption of flavonoid-rich dark chocolate blunted the acute prothrombotic response to psychosocial stress, thereby perhaps mitigating the risk of acute coronary syndromes triggered by emotional stress.

Comparison of cytotoxic and anti-platelet activities of polyphenolic extracts from Arnica montana flowers and Juglans regia husks

Polyphenolic compounds of plant origin are well known to be beneficial to human health: they exert protective effects on haemostasis and have a particular influence on blood platelets. However, the anti-platelet properties of polyphenolic compounds observed so far have not been weighed against their potential cytotoxic action against platelets. The aim of this study was to demonstrate that anti-platelet and cytotoxic effects on blood platelets may interfere and therefore, may often lead to confusion when evaluating the properties of plant extracts or other agents towards blood platelets. The anti-platelet and cytotoxic in vitro effects of plant extracts obtained from the husks of walnuts (J. regia) and flowers of arnica (A. montana) on platelet reactivity and viability were examined. Platelet function was assessed using standard methods (flow cytometry: P-selectin expression, activation of GPIIbIIIa complex, vasodilator-stimulated phosphoprotein, VASP index; turbidimetric and impedance aggregometry) and newly set assays (flow cytometric monitoring of platelet cytotoxicity). The results reveal that none of the studied plant extracts demonstrated cytotoxicity towards blood platelets. The phenolic acid-rich extract of A. montana (7.5 and 15 µg/ml) significantly reduced the ADP-induced aggregation in both whole blood and PRP, and decreased the platelet reactivity index (PRI; VASP phosphorylation) in whole blood, while showing excellent antioxidant capacity. The extract of J. regia husks significantly reduced ADP-induced platelet aggregation in whole blood when applied at 7.5 µg/ml, and only slightly decreased the PRI at 15 µg/ml. Both examined extracts suppressed platelet hyper-reactivity, and such influence did not interfere with cytotoxic effects of the extracts. Thus, its high polyphenol content, excellent antioxidant capacity and distinct anti-platelet properties, in combination with its lack of toxicity, make the extract of A. montana flowers a possible candidate as an anti-platelet agent or a compounding diet supplement.

Extract of Aronia melanocarpa-modified hemostasis: in vitro studies

Purpose

Aronia melanocarpa has an extremely high content of procyanidins and anthocyanins. The multidirectional benefits of consumption of these berries are widely reported. Although numerous studies confirmed the influence of polyphenols on various stages of hemostasis, the exact mechanism of this phenomenon is not understood. The aim of our study was to evaluate the in vitro effect of A. melanocarpa extract on various parameters of hemostasis.

Methods

Adenosine 5′-diphosphate (ADP)-induced aggregation was measured with turbidimetric method. Spontaneous and ADP-activated platelet adhesion were investigated using a colorimetric method. The global assay of coagulation and fibrinolysis was performed with the use of optical clotting and lysis (CL) test. Thrombin (0.5 IU/mL) and tissue plasminogen activator (60 ng/mL) were used to obtain a CL curve. The activity of thrombin and plasmin was determined by means of chromogenic substrate (S-2238, S-2251)

Results

The aronia extract contributed to the reduction in spontaneous and ADP-activated platelet adhesion. A significant increase in overall potential of CL as well as significant changes in key parameters of these processes (T_t—thrombin time, F_vo—initial plasma clotting velocity, and L_max—maximum lysis) was reported. Chokeberry extract significantly inhibited the amidolytic activity of thrombin and plasmin.

Conclusion

Our in vitro findings indicate a complex mechanism of influence of chokeberry polyphenols on platelet activity and the overall potential of CL. We confirmed that chokeberry inhibits the amidolytic activity of thrombin. It was demonstrated for the first time that chokeberry polyphenols inhibit the amidolytic activity of another serine protease, i.e., plasmin, which is the main fibrinolytic enzyme. Furthermore, our research points out a significant contribution of other plasma components and fibrinogen in the modulation of hemostasis by polyphenols.

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.

Chlorogenic acid inhibits human platelet activation and thrombus formation

BACKGROUND

Chlorogenic acid is a potent phenolic antioxidant. However, its effect on platelet aggregation, a critical factor in arterial thrombosis, remains unclear. Consequently, chlorogenic acid-action mechanisms in preventing platelet activation and thrombus formation were examined.

METHODS AND RESULTS

Chlorogenic acid in a dose-dependent manner (0.1 to 1 mmol/L) inhibited platelet secretion and aggregation induced by ADP, collagen, arachidonic acid and TRAP-6, and diminished platelet firm adhesion/aggregation and platelet-leukocyte interactions under flow conditions. At these concentrations chlorogenic acid significantly decreased platelet inflammatory mediators (sP-selectin, sCD40L, CCL5 and IL-1β) and increased intraplatelet cAMP levels/PKA activation. Interestingly, SQ22536 (an adenylate cyclase inhibitor) and ZM241385 (a potent A2A receptor antagonist) attenuated the antiplatelet effect of chlorogenic acid. Chlorogenic acid is compatible to the active site of the adenosine A2A receptor as revealed through molecular modeling. In addition, chlorogenic acid had a significantly lower effect on mouse bleeding time when compared to the same dose of aspirin.

CONCLUSIONS

Antiplatelet and antithrombotic effects of chlorogenic acid are associated with the A2A receptor/adenylate cyclase/cAMP/PKA signaling pathway.

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.

Evaluating the antioxidative activity of diselenide containing compounds in human blood

This study was designed to determine and compare the antioxidant effects of synthetic organoselenium compounds. In experimental trials three different diselenides were used: bis(2-hydroxyphenyl) diselenide, bis{[2-(4-hydroxybenzyl)imino]phenyl} diselenide and bis[2-(4-methylphenylsulfonylamino)phenyl] diselenide. The compounds were screened for antioxidant activities in human blood under oxidation stress conditions. Oxidative stress was induced in vitro in human blood platelet samples and in plasma by 0.1 mM peroxynitrite (ONOO(-)) or by Fe(2+). In experimental trials the levels of chosen oxidative stress markers (TBARS, O2(-), and protein carbonyl groups) were significantly decreased by the action of the tested compounds. The antioxidative properties and the changes in proteins and lipids in the presence of new synthesized selenoorganic compounds were studied in vitro and compared with activity of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one)--a classical antioxidant, well known as the most important glutathione peroxidase mimetic agent. Our results indicate that the tested diselenides have distinctly protective effects against oxidative alterations of biomolecules caused by ONOO(-) and Fe(2+) in blood platelets and in plasma. Therefore it seems that not only ebselen with a wide spectrum of therapeutic actions but also other organoselenium compounds can be considered in the future as active pharmacological agents.

The influence of conjugates isolated from Matricaria chamomilla L. on platelets activity and cytotoxicity

Cardiovascular diseases (CVD) remain the principal cause of death in both advanced and developing countries of the world. Blood platelets are involved in the pathogenesis of atherosclerosis and thrombosis. Platelet adhesion and aggregation are critical events that occur in unstable coronary syndromes. The current research is focused on the role of polysaccharide-polyphenolic conjugates isolated from chamomile (Matricaria chamomilla L.) at concentrations of 10, 25, 50 and 100 μg/mL on blood platelets (obtained from healthy donors and from patients received combined anti-platelet therapy complex with clopidogrel and acetylsalicylic acid) aggregation and experimentally induced cell toxicity. The treatment of PRP obtained from healthy donors with polyphenolic-polysaccharide conjugates from M. chamomilla (L.) (MC) resulted in a dose-dependent, decrease of platelet aggregation induced by multiple agonists (ADP, collagen and arachidonic acid). In this study we also observed that the MC reduced platelet aggregation in PRP obtained from patients with cardiovascular disorders. The result of testing the MC on human blood platelets, mouse fibroblast cultures L929 and human lung cells A549 did not show any cytotoxicity effects. Compounds obtained from M. chamomilla L. are potential composite to the development of a new anti-platelet agent, which could be an alternative to the currently used anti-platelet drugs.

Aronia melanocarpa as a protector against nitration of fibrinogen

Fibrinogen (Fg) also known as coagulation factor I represents about 4% of the total human plasma proteins. The main function of Fg is its involvement in last phase of blood coagulation cascade, when thrombin-induced conversion of dissolved plasma fibrinogen into an insoluble fibrin clot occurs. The reaction of fibrinogen with peroxynitrite causes both structural modifications and changes of the biological properties of this plasma glycoprotein. Recently, there is an increased interest in the screening of natural products present in fruits, vegetables and herbs for their possible antioxidative activities. Therefore, the aim of our study was to estimate the effect of extract from berries of Aronia melanocarpa against nitrative and oxidative damage induced by peroxynitrite. The extract from A. melanocarpa (0.5-50 μg/ml) added to Fg 10 min before peroxynitrite (100 μM) significantly inhibited both the formation of the high molecular weight protein aggregates and nitration of Fg molecule. The extract also abolished peroxynitrite-induced inhibition of fibrinogen polymerization (by 95% at 50 μg/ml). The obtained results indicate that natural extract from berries of A. melanocarpa has protective effects against peroxynitrite-induced nitrative damage of plasma fibrinogen, and therefore may contribute in the prevention of peroxynitrite-related cardiovascular or inflammatory diseases.