In Vivo Anticoagulant and Thrombolytic Activities of a Fibrinolytic Serine Protease (Brevithrombolase) With the k-Carrageenan-Induced Rat Tail Thrombosis Model

Studies on in vivo antithrombotic activity of quercetin, a natural flavonoid isolated from a traditional medicinal plant, African eggplant (Solanum indicum)

ETHNOPHARMACOLOGICAL RELEVANCE

Every year, cardiovascular diseases (CVDs) account for about 17.9 million deaths, making them the primary cause of both morbidity and mortality. Conventional drugs, which are often prescribed to treat cardiovascular diseases, are costly and have adverse effects. Consequently, dietary modifications and other medications are needed. Traditional use of Solanum indicum as cardiotonic to treat hypertension and anticoagulant potency has been reported but poorly evaluated scientifically.

AIM OF THE STUDY

This study investigated the in vivo anticoagulant activity and mechanism of anticoagulation of quercetin (QC), a bioactive compound isolated from S. indicum (SI) hydroethanolic fruit extract.

MATERIALS AND METHODS

Bioassay-guided fractionation (anticoagulant activity) extracted QC from hydroethanolic SI extract. QC was extensively characterized biochemically and pharmacologically. The interaction between QC and thrombin was investigated using spectrofluorometric and isothermal calorimetric methods. Cytotoxicity, antiplatelet, and thrombolytic studies were carried out in vitro. The Swiss albino mice were used to assess the in vivo, anticoagulant, and antithrombotic activities of QC.

RESULTS

QC exhibits anticoagulant activity via (i) uncompetitive inhibition of thrombin but not FXa with a Ki value of 33.11 ± 4.2 μM and (ii) a partial inhibition of thrombin-catalyzed platelet aggregation with an IC50 value of 13.2 ± 1.2 μM. The experimental validation of the in silico study's prediction of QC's binding to thrombin was confirmed by spectrofluorometric and isothermal calorimetric analyses. QC was nontoxic to mammalian, non-hemolytic cells and demonstrated thrombolytic activity by activating plasminogen. QC demonstrated in vivo anticoagulant efficacy, preventing k-carrageen-induced thrombus formation in mice's tails. In the acute circulatory stasis paradigm in mice, QC reduces thromboxane B2 (TXB2) and endothelin-1 (ET-1) while increasing nitric oxide synthase (eNOS) and 6-keto prostaglandin F1α (6-keto-PGF1 α).

CONCLUSION

Effective in vivo anticoagulant and antithrombotic properties of S. indicum's bioactive component QC point to the plant's potential use as a herbal anticoagulant medication for preventing and treating cardiovascular diseases linked to thrombosis.

Toxicological assays in the evaluation of safety assessment of fibrinolytic enzymes

Cardiovascular diseases (CVDs) cause 30% of deaths each year, and in 2030, around 23.6 million people will die due to CVDs. The major challenge is to obtain molecules with minimal adverse reactions that can prevent and dissolve blood clots. In this context, fibrinolytic enzymes from diverse microorganism sources have been extensively investigated due to their potential to act directly and specifically on the fibrin clot, preventing side effects and performing potential thrombolytic effects. However, most researches focus on the purification and characterization of proteases, with little emphasis on the mechanism of action and pharmacological characteristics, including toxicity assays which are essential to assess safety and side effects. Therefore, this work aims to emphasize the importance of evaluations indicating the toxicological profile of fibrinolytic proteases through in vitro and in vivo tests. Both types of assays contribute as preclinical stage in drug development and are crucial for clinical applications. This scarcity creates arbitrary barriers to further studies. This work should further encourage the development of studies to ensure the safety and effectivity of fibrinolytic proteases.

Computational analysis to comprehend the structure-function properties of fibrinolytic enzymes from Bacillus spp for their efficient integration into industrial applications

Background

The fibrinolytic enzymes from Bacillus sp. are proposed as therapeutics in preventing thrombosis. Computational-based analyses of these enzymes' amino acid composition, basic physiological properties, presence of functional domain and motifs, and secondary and tertiary structure analyses can lead to developing a specific enzyme with improved catalytic activity and other properties that may increase their therapeutic potential.

Methods

The nucleotide sequences of fibrinolytic enzymes produced by the genus Bacillus and its corresponding protein sequences were retrieved from the NCBI database and aligned using the PRALINE programme. The varied physiochemical parameters and structural and functional analysis of the enzyme sequences were carried out with the ExPASy-ProtParam tool, MEME server, SOPMA, PDBsum tool, CYS-REC tool, SWISS-MODEL, SAVES servers, TMHMM program, GlobPlot, and peptide cutter software. The assessed in-silico data were compared with the published experimental results for validation.

Results

The alignment of sixty fibrinolytic serine protease enzymes (molecular mass 12-86 kDa) sequences showed 49 enzymes possess a conserved domain with a catalytic triad of Asp196, His242, and Ser569. The predicted instability and aliphatic indexes were 1.94-37.77, and 68.9-93.41, respectively, indicating high thermostability. The random coil means value suggested the predominance of this secondary structure in these proteases. A set of 50 amino acid residues representing motif 3 signifies the Peptidase S8/S53 domain that was invariably observed in 56 sequences. Additionally, 28 sequences have transmembrane helices, with two having the most disordered areas, and they pose 25 enzyme cleavage sites. A comparative analysis of the experimental work with the results of in-silico study put forward the characteristics of the enzyme sequences JF739176.1 and MF677779.1 to be considered when creating a potential mutant enzyme as these sequences are stable at high pH with thermostability and to exhibit αβ-fibrinogenase activity in both experimental and in-silico studies.

Ion-Exchange Resin/Carrageenan-Copper-Based Nanocomposite: Artificial Neural Network, Advanced Thermodynamic Profiling, and Anticoagulant Studies

Carrageenan (CG) and ion exchange resins (IERs) are better metal chelators. Kappa (κ) CG and IERs were synthesized and subjected to copper ion (Cu2+) adsorption to obtain DMSCH/κ-Cu, DC20H/κ-Cu, and IRP69H/κ-Cu nanocomposites (NCs). The NCs were studied using statistical physics formalism (SPF) at 315-375 K and a multilayer perceptron with five input nodes. The percentage of Cu2+ uptake efficiency was used as an outcome variable. Via the grand canonical ensemble, SPF gives models for both monolayer and multilayer sorption layers. For in vitro anticoagulant activity (ACA), the activated partial thromboplastin time were calculated using 100 μL of rabbit plasma incubated at 37 °C. After 2 min, 100 L of 0.025 M CaCl2 was added, and the clotting time was recorded for each group (n = 6). The results demonstrated that the key covariables for the adsorption process were pH and concentration. The results of artificial neural network models were comparable with the experimental findings. The error rates varied between 4.3 and 1.0%. The prediction analysis results ranged from 43.6 to 89.2. The ΔG and ΔS values for IRP69H/κ-Cu obtained were -18.91 and -16.32 and 26.21 and 22.74 kJ/mol for the temperatures 315 and 345 K, respectively. Adsorbate species were perpendicular to the adsorbent surfaces, notwithstanding the apparent importance of macro- and micropore volumes. These adsorbents typically fluctuate with temperature changes and contain one or more layers of sorption. Negative and positive sorption energies correspond to endothermic and exothermic processes. The biosorption energy (E1 and E2) values in this experiment have a value of less than 23 kJ mol-1. Complex SPF models' energy distributions validate surface properties and interactions with adsorbates. At a concentration of 100 μg/mL, DC20H/κ-Cu2+ exhibited an ACA of only 8 s. These NCs demonstrated better greater ACA with the order DC20H/κ < DMSCH/κ < IRP69H/κ. More research is needed to rule out the chemical processes behind the ACA of CG/IER-Cu NCs.

Water-soluble tomato concentrate modulates shear-induced platelet aggregation and blood flow in vitro and in vivo

Water-soluble tomato concentrate (WSTC), extracted from mature tomatoes, is the first health product in Europe that has been approved “to help maintain normal platelet activity to maintain healthy blood flow.” We hypothesized that WSTC might exert an influence on blood flow shear stress-induced platelet aggregation (SIPA) and in turn maintains healthy blood flow. We used a microfluidic system to measure the effects of WSTC on SIPA in vitro. We also used the strenuous exercise rat model and the κ-carrageenan-induced rat tail thrombosis model to demonstrate the effects of WSTC on blood flow. WSTC significantly inhibited platelet aggregation at pathological high shear rate of 4,000 s–1 and 8,000 s–1in vitro (P &lt; 0.05 or P &lt; 0.01). WSTC reduced the platelet adhesion rate and increased the rolling speed of platelets by inhibiting binding to Von Willebrand Factor (vWF) (P &lt; 0.05 or P &lt; 0.01). The oral administration of WSTC for 4 weeks in strenuous exercise rats alleviated hyper-reactivity of the platelets and led to a significant reduction in the plasma levels of catecholamine and IL-6. WSTC treatment also led to a reduction in black tail length, reduced blood flow pulse index (PI) and vascular resistance index (RI), and ameliorated local microcirculation perfusion in a rat model of thrombosis. WSTC exerted obvious inhibitory effects on the platelet aggregation induced by shear flow and alleviated the blood flow and microcirculation abnormities induced by an inflammatory reaction.

Microbial Fibrinolytic Enzymes as Anti-Thrombotics: Production, Characterisation and Prodigious Biopharmaceutical Applications

Cardiac disorders such as acute myocardial infarction, embolism and stroke are primarily attributed to excessive fibrin accumulation in the blood vessels, usually consequential in thrombosis. Numerous methodologies including the use of anti-coagulants, anti-platelet drugs, surgical operations and fibrinolytic enzymes are employed for the dissolution of fibrin clots and hence ameliorate thrombosis. Microbial fibrinolytic enzymes have attracted much more attention in the management of cardiovascular disorders than typical anti-thrombotic strategies because of the undesirable after-effects and high expense of the latter. Fibrinolytic enzymes such as plasminogen activators and plasmin-like proteins hydrolyse thrombi with high efficacy with no significant after-effects and can be cost effectively produced on a large scale with a short generation time. However, the hunt for novel fibrinolytic enzymes necessitates complex purification stages, physiochemical and structural-functional attributes, which provide an insight into their mechanism of action. Besides, strain improvement and molecular technologies such as cloning, overexpression and the construction of genetically modified strains for the enhanced production of fibrinolytic enzymes significantly improve their thrombolytic potential. In addition, the unconventional applicability of some fibrinolytic enzymes paves their way for protein hydrolysis in addition to fibrin/thrombi, blood pressure regulation, anti-microbials, detergent additives for blood stain removal, preventing dental caries, anti-inflammatory and mucolytic expectorant agents. Therefore, this review article encompasses the production, biochemical/structure-function properties, thrombolytic potential and other surplus applications of microbial fibrinolytic enzymes.

Thrombolytic Enzymes of Microbial Origin: A Review

Enzyme therapies are attracting significant attention as thrombolytic drugs during the current scenario owing to their great affinity, specificity, catalytic activity, and stability. Among various sources, the application of microbial-derived thrombolytic and fibrinolytic enzymes to prevent and treat vascular occlusion is promising due to their advantageous cost-benefit ratio and large-scale production. Thrombotic complications such as stroke, myocardial infarction, pulmonary embolism, deep venous thrombosis, and peripheral occlusive diseases resulting from blood vessel blockage are the major cause of poor prognosis and mortality. Given the ability of microbial thrombolytic enzymes to dissolve blood clots and prevent any adverse effects, their use as a potential thrombolytic therapy has attracted great interest. A better understanding of the hemostasis and fibrinolytic system may aid in improving the efficacy and safety of this treatment approach over classical thrombolytic agents. Here, we concisely discuss the physiological mechanism of thrombus formation, thrombo-, and fibrinolysis, thrombolytic and fibrinolytic agents isolated from bacteria, fungi, and algae along with their mode of action and the potential application of microbial enzymes in thrombosis therapy.

Role of Fibrinolytic Enzymes in Anti-Thrombosis Therapy

Thrombosis, a major cause of deaths in this modern era responsible for 31% of all global deaths reported by WHO in 2017, is due to the aggregation of fibrin in blood vessels which leads to myocardial infarction or other cardiovascular diseases (CVDs). Classical agents such as anti-platelet, anti-coagulant drugs or other enzymes used for thrombosis treatment at present could leads to unwanted side effects including bleeding complication, hemorrhage and allergy. Furthermore, their high cost is a burden for patients, especially for those from low and middle-income countries. Hence, there is an urgent need to develop novel and low-cost drugs for thrombosis treatment. Fibrinolytic enzymes, including plasmin like proteins such as proteases, nattokinase, and lumbrokinase, as well as plasminogen activators such as urokinase plasminogen activator, and tissue-type plasminogen activator, could eliminate thrombi with high efficacy rate and do not have significant drawbacks by directly degrading the fibrin. Furthermore, they could be produced with high-yield and in a cost-effective manner from microorganisms as well as other sources. Hence, they have been considered as potential compounds for thrombosis therapy. Herein, we will discuss about natural mechanism of fibrinolysis and thrombus formation, the production of fibrinolytic enzymes from different sources and their application as drugs for thrombosis therapy.

Novel Hyp-Gly-containing antiplatelet peptides from collagen hydrolysate after simulated gastrointestinal digestion and intestinal absorption

Bioactive components causing the antiplatelet activity upon collagen hydrolysate (CH) ingestion have not been clarified yet. This study aimed to identify antiplatelet peptides from CH after simulated gastrointestinal digestion and intestinal absorption. Four antiplatelet peptides containing the Hyp-Gly (OG) sequence including OG, Hyp-Gly-Glu (OGE), Pro-Gly-Glu-Hyp-Gly (PGEOG) and Val-Gly-Pro-Hyp-Gly-Pro-Ala (VGPOGPA) were successfully identified. All four peptides exhibited antiplatelet activity, but OGE and PGEOG exerted stronger activity than OG and VGPOGPA. The IC50 value of OGE and PGEOG was 1.076 mM and 1.167 mM, respectively. These four antiplatelet peptides could survive simulated gastrointestinal digestion and be absorbed intact by Caco-2 cells. Furthermore, plasma stability experiments showed that OG and OGE showed a good stability in human plasma, but PGEOG and VGPOGPA showed a relatively poor stability. In vivo studies indicated that OG and OGE were present in blood after the oral administration of CH. Meanwhile, OGE exerted significant in vivo anti-thrombotic activity after its ingestion. The present study clarifies the antiplatelet components causing the CH activity and highlights the potential application of CH or these four peptides as functional foods to combat thrombosis by inhibiting platelet aggregation.

Cloning, purification and characterization of a recombinant protease with novel thrombolytic activity in human plasma and rat thrombosis models

BACKGROUND

There is a need to identify and develop novel thrombolytic agents that can directly digest fibrin clots from various biological resources.

OBJECTIVE

To clone, express, purify, and characterize a recombinant protease named rvFMP capable of cleaving fibrinogen, fibrin polymer, and cross-linked fibrin in human plasma milieu and rat thrombosis model systems.

RESULTS

We cloned a vFMP-encoding gene from the genomic DNA of V. furnissii KCCM41679 using polymerase chain reaction (PCR), expressed in Escherichia coli, and purified rvFMP (stands for recombinant vibrio furnissii metalloprotease). The proteolytic activity of purified rvFMP enzyme could be clearly inhibited by 1,10-phenanthroline and ethylene glycol tetraacetic acid, but not by diisopropyl fluorophosphate, suggesting that it can be a typical metalloprotease. rvFMP showed an effective proteolytic activity in cleaving cross-linked fibrins in human plasma milieu. Remarkably, rvFMP exhibited a clear thrombolytic activity in rat thrombosis models such as ferric chloride-exposed rat carotid artery and carrageenan-treated rat tail. However, rvFMP (1.5 mg/kg) evoked no internal bleeding and also showed no lethal effect in mice. The recombinant enzyme also showed no cytotoxicity and had an inability to induce tumour necrosis factor-α (TNF-α) in Raw264.7 cells.

CONCLUSION

rvFMP can be a candidate enzyme capable of being developed as a novel direct-acting thrombolytic agent.

Characterization of active anticoagulant fraction and a fibrin(ogen)olytic serine protease from leaves of Clerodendrum colebrookianum, a traditional ethno-medicinal plant used to reduce hypertension

ETHNOPHARMACOLOGICAL RELEVANCE

Cardiovascular diseases are the major cause of mortality and morbidity, causing over 17.9 million deaths a year worldwide. Currently used therapy is often having side effects and expensive, dietary interventions and alternative medicines are required. Clerodendrum colebrookianum has been used to treat cardiac hypertension but anticoagulant potency was not evaluated.

AIM OF THE STUDY

To characterize an active anticoagulant fraction (AAFCC) and a 30 kDa fibrin(ogen)olytic serine protease (clerofibrase) isolated from aqueous leave extract of C. colebrookianum.

MATERIALS AND METHODS

AAFCC/clerofibrase was subjected to extensive biochemical and pharmacological characterization including LC-MS/MS, amino acid compositional and GC-MS analyses. Interaction between clerofibrase with fibrinogen was studied by spectrofluorometric analysis. In vitro thrombolytic, antiplatelet and cytotoxicity assay were performed. In vivo toxicity, anticoagulant, defibrinogen and antithrombotic activities were determined on Swiss albino mice.

RESULTS

The in vitro anticoagulant activity of AAFCC was found to be superior to heparin and clerofibrase and comparable to Nattokinase and warfarin. The proteomics and amino acid composition analyses suggest that clerofibrase is a previously uncharacterized novel plant protease capable of degrading the -αβ chains of fibrinogen/fibrin. AAFCC/clerofibrase exerts their anticoagulant action via fibrinogenolytic activity and partially by antiplatelet activity albeit they have no effect on thrombin and FXa inhibition. The spectrofluorometric analysis revealed the binding of clerofibrase to fibrinogen but not to thrombin and FXa. The phytochemical constituents and bioactive components of AAFCC were characterized by biochemical, and GC-MS analyses. The AAFCC and clerofibrase inhibited collagen/ADP-induced mammalian platelet aggregation, showed in vitro thrombolytic activity, and non-cytotoxic to mammalian cells. The AAFCC showed and dose-dependent in vivo plasma defibrinogenating and anticoagulant activities and inhibited k-carrageen-induced thrombus formation in the tails of mice.

CONCLUSION

The potent in vivo anticoagulant and antithrombotic effects of AAFCC suggests its pharmacological significance as herbal anticoagulant drug for the prevention and/or treatment of hyperfibrinogenemia- and thrombosis associated cardiovascular disorders.

Antithrombotic Effect of Artemisia princeps Pampanini Extracts in Vitro and in FeCl3 -Induced Thrombosis Rats

Extracts of several plants possess antithrombotic effects. Herein, we examined the antithrombotic effects of different extracts of Artemisia princeps Pampanini prepared using distilled water, hot distilled water, 70% ethanol, or subcritical water. The antithrombotic effects were determined using a co-culture system consisting of tumor necrosis factor-alpha (TNF-α)-treated EA.hy926 cells and THP-1 cells. In addition, the coagulation time of plasma collected from healthy volunteers was evaluated in terms of the prothrombin time and activated partial thromboplastin time. A carotid arterial thrombosis model was induced by ferric chloride in Sprague Dawley rats. The rats were treated with either sterile water or three different doses of the subcritical water extract for 2 weeks. The thrombus weight, gene expression of cell adhesion molecules, and histological characteristics were assessed. The results of in vitro studies revealed a significant inhibition in the adhesion of monocytes to EA.hy926 cells stimulated by TNF-α in the subcritical water extract-treated group. We also observed considerable suppression of the occlusion and mRNA expression of cell adhesion molecules in the in vivo experiments. This study suggests that Artemisia princeps Pampanini may have the potential to improve blood coagulation.

First Report of Plant-Derived β-Sitosterol with Antithrombotic, in Vivo Anticoagulant, and Thrombus-Preventing Activities in a Mouse Model

Inhibitors of thrombin, a key enzyme in the blood coagulation cascade, are of great interest because of their selective specificity and effectiveness in anticoagulation therapy against cardiovascular disorders. The natural soybean phytosterol, β-sitosterol (BSS) demonstrated anticoagulant activity by dose-dependent inhibition of thrombin in an uncompetitive manner with a K_i value of 0.267 μM as well as by partial inhibition of thrombin-catalyzed platelet aggregation with a half-maximal inhibitory concentration (IC₅₀) value of 10.45 ± 2.88 μM against platelet-rich plasma and 9.2 ± 1.2 μM against washed platelets. An in silico study indicated binding of BSS to thrombin, which was experimentally verified by spectrofluorometric and isothermal calorimetric analyses. Under in vitro conditions, BSS demonstrated thrombolytic activity by activating plasminogen, albeit it is devoid of protease (fibrinogenolytic) activity. BSS was noncytotoxic to mammalian cells, nonhemolytic, demonstrated its in vivo anticoagulant activity when administered orally, and inhibited k-carrageen-induced thrombus formation in the tails of mice. Our results suggest that dietary supplementation of BSS may help to prevent thrombosis-associated cardiovascular disorders.

Anticoagulant mechanism, pharmacological activity, and assessment of preclinical safety of a novel fibrin(ogen)olytic serine protease from leaves of Leucas indica

The harnessing of medicinal plants containing a plethora of bioactive molecules may lead to the discovery of novel, potent and safe therapeutic agents to treat thrombosis-associated cardiovascular diseases. A 35 kDa (m/z 34747.5230) serine protease (lunathrombase) showing fibrin(ogen)olytic activity and devoid of N- and O- linked oligosaccharides was purified from an extract of aqueous leaves from L. indica. The LC-MS/MS analysis, de novo sequencing, secondary structure, and amino acid composition determination suggested the enzyme’s novel characteristic. Lunathrombase is an αβ-fibrinogenase, demonstrating anticoagulant activity with its dual inhibition of thrombin and FXa by a non-enzymatic mechanism. Spectrofluorometric and isothermal calorimetric analyses revealed the binding of lunathrombase to fibrinogen, thrombin, and/or FXa with the generation of endothermic heat. It inhibited collagen/ADP/arachidonic acid-induced mammalian platelet aggregation, and demonstrated antiplatelet activity via COX-1 inhibition and the upregulation of the cAMP level. Lunathrombase showed in vitro thrombolytic activity and was not inhibited by endogenous protease inhibitors α₂ macroglobulin and antiplasmin. Lunathrombase was non-cytotoxic to mammalian cells, non-hemolytic, and demonstrated dose-dependent (0.125–0.5 mg/kg) in vivo anticoagulant and plasma defibrinogenation activities in a rodent model. Lunathrombase (10 mg/kg) did not show toxicity or adverse pharmacological effects in treated animals.

The N-terminal-truncated recombinant fibrin(ogen)olytic serine protease improves its functional property, demonstrates in vivo anticoagulant and plasma defibrinogenation activity as well as pre-clinical safety in rodent model

An N-terminal truncated fibrino(geno)lytic serine protease gene encoding a ~42kDa protein from Bacillus cereus strain AB01 was produced by error prone PCR, cloned into pET19b vector, and expressed in E5 coli BL21 DE3 cells. The deletion of 24 amino acid residues from N-terminal of wild-type Bacifrinase improves the catalytic activity of [Bacifrinase (ΔN24)]. The anticoagulant potency of [Bacifrinase (ΔN24)] was comparable to Nattokinase and Warfarin and results showed that its anticoagulant action is contributed by progressive defibrinogenation and antiplatelet activities. Nonetheless, at the tested concentration of 2.0μM [Bacifrinase (ΔN24)] did not show in vitro cytotoxicity or chromosomal aberrations on human embryonic kidney cells-293 (HEK-293) and human peripheral blood lymphocytes (HPBL) cells. [Bacifrinase (ΔN24)], at a dose of 2mg/kg, did not show toxicity, adverse pharmacological effects, tissue necrosis or hemorrhagic effect after 72h of its administration in Swiss albino mice. However, at the tested doses of 0.125 to 0.5mg/kg, it demonstrated significant in anticoagulant effect as well as defibrinogenation after 6h of administration in mice. We propose that [Bacifrinase (ΔN24)] may serve as prototype for the development of potent drug to prevent hyperfibrinogenemia related disorders.

Global deregulation of ginseng products may be a safety hazard to warfarin takers: solid evidence of ginseng-warfarin interaction

Recent global deregulation of ginseng as the table food raises our concern about the possible ginseng-warfarin interaction that could be life-threatening to patients who take warfarin for preventing fatal strokes and thromboembolism while using ginseng products for bioenergy recovery. Here we show that quality-control ginsenosides, extracted from ginseng and containing its major active ingredients, produce dose- and time-dependent antagonism in rats against warfarin's anti-coagulation assessed by INR and rat thrombosis model. The interactions between ginsenosides and warfarin on thrombosis, pharmacokinetics, activities of coagulation factors and liver cytochrome P450 isomers are determined by using thrombosis analyzer, UPLC/MS/MS, ELISA and real-time PCR, respectively. The antagonism correlates well with the related pharmacokinetic interaction showing that the blood plateaus of warfarin reached by one-week warfarin administration are significantly reduced after three-week co-administration of warfarin with ginsenosides while 7-hydroxywarfarin is increased. The one-week warfarin and three-week warfarin-ginsenosides regimen result in restoring the suppressed levels by warfarin of the coagulating factors II, VII and protein Z, and significantly enhance activities of P450 3A4 and 2C9 that metabolize warfarin. The present study, for the first time, provides the solid evidence to demonstrate the warfarin-ginsenoside interaction, and warns the warfarin users and regulation authorities of the dangerous interaction.

Evaluation on antithrombotic effect of aspirin eugenol ester from the view of platelet aggregation, hemorheology, TXB2/6-keto-PGF1α and blood biochemistry in rat model

Background

Based on the prodrug principle, aspirin and eugenol, as starting precursors, were esterified to synthesize aspirin eugenol ester (AEE). The aim of the present study was to evaluate the antithrombotic effect of AEE in an animal disease model. In order to compare the therapeutic effects of AEE and its precursors, aspirin, eugenol and a combination of aspirin and eugenol were designed at the same molar quantities as the AEE medium dose in the control group.

Methods

After oral administration of AEE (dosed at 18, 36 and 72 mg/kg) for seven days, rats were treated with k-carrageenan to induce tail thrombosis. Following the same method, aspirin (20 mg/kg), eugenol (18 mg/kg) and 0.5 % CMC-Na (30 mg/kg) were administered as control drug. Different drug effects on platelet aggregation, hemorheology, TXB₂/6-keto-PGF_1α ratio and blood biochemistry were studied.

Results

AEE significantly inhibited ADP and AA-induced platelet aggregation in vivo. AEE also significantly reduced blood and plasma viscosity. Moreover, AEE down-regulated TXB₂ and up-regulated 6-keto-PGF_1α, normalizing the TXB₂/6-keto-PGF_1α ratio and blood biochemical profile. In comparison with aspirin and eugenol, AEE produced more positive therapeutic effects than its precursors under the same molar quantity.

Conclusion

It may be concluded that AEE was a good candidate for new antithrombotic and antiplatelet medicine. Additionally, this study may help to understand how AEE works on antithrombosis in different ways.