Anticoagulant, anti-aggregation and antithrombotic effects of a novel hexapeptide

Objectives Hexapeptide is a novel synthetic oligopeptide with a structure similar to that of eptifibatide. This study was designed to investigate the anticoagulant, anti‐aggregation, disaggregation and anti‐thrombogenesis effects of hexapeptide. Methods The effects of antiplatelet aggregation induced by adenosine diphosphate (ADP), arachidonic acid (AA) and thrombin, and the effect of disaggregation of platelet aggregation induced by ADP were determined. The anticoagulation indexes were determined by different kits. Key findings Hexapeptide 1 × 10^?5–1 × 10^?4m could significantly prolong rabbit blood clotting time, thrombin time, prothrombin time and activated partial thromboplastin enzyme time, and reduce the length, wet weight, dry weight and the index of thrombus in a concentration‐dependent manner. Hexapeptide 1 × 10^?4m decreased platelet adhesion rate by 40.2%. The platelet aggregation inhibition of hexapeptide in dogs and humans was more obvious than in rabbits and rats. The aggregation inhibition rate of 1 × 10^?5m hexapeptide in dogs, rabbits, rats and humans induced by ADP was 93.9 ± 1.3%, 66.2 ± 1.4%, 76.1 ± 3.2% and 99.8 ± 0.2%, respectively; the 50% inhibitory concentration (IC50) of hexapeptide was 7.24 × 10^?8, 3.24 × 10^?6, 6.61 × 10^?6 and 8.91 × 10^?8m , respectively. For the aggregation inhibition rate of hexapeptide in dogs, rabbits and humans induced by AA, the IC50 was 1.29 × 10^?9, 1.32 × 10^?6 and 9.33 × 10^?8m , respectively; the IC50 of aggregation inhibition rates induced by thrombin was 2.88 × 10^?6, >1 × 10^?5 and 4.17 × 10^?6m , respectively. The disaggregation rate of 1 × 10^?4m hexapeptide in dog induced by ADP was 68.8 ± 7.4%. Conclusions Hexapeptide has anticoagulant, antiplatelet aggregation, disaggregation and antithrombotic effects in vitro.     

Antiplatelet effects of piplartine,an alkamide isolated from Piper tuberculatum: possible involvement of cyclooxygenase blockade and antioxidant activity

Objectives Piplartine (piperlongumine; 5,6‐dihydro‐1‐[1‐oxo‐3‐(3,4,5‐trimethoxyphenyl]‐2(1H) pyridinone) is an alkaloid amide isolated from Piper species (Piperaceae). It has been reported to show multiple pharmacological activities in vitro and in vivo. Methods We evaluated the in‐vitro antiplatelet effect of piplartine isolated from the roots of P. tuberculatum, on human platelet aggregation induced in platelet‐rich plasma by the agonists collagen, adenosine 5′‐diphosphate (ADP), arachidonic acid (AA) and thrombin. Key findings Piplartine (100μg/ml) caused a 30% inhibition in platelet aggregation when collagen was the agonist. At 200 μg/ml, piplartine significantly inhibited the aggregation induced by arachidonic acid (100%), collagen (59%) or ADP (52%) but not that induced by thrombin. The highest concentration of piplartine (300 μg/ml) inhibited thrombin‐ (37%), ADP‐ (71%) and collagen‐ (98%) induced aggregation. The inhibitory effect of piplartine on ADP‐induced platelet aggregation was not modified by pretreatment with pentoxifylline (a phosphodiesterase inhibitor), l ‐arginine (a substrate for nitric oxide synthase) or ticlopidine (a P2Y₁₂ purinoceptor antagonist). However, aspirin, a well‐known inhibitor of cyclooxygenase, greatly increased the inhibitory effect of piplartine on arachidonic‐acid‐induced platelet aggregation. Conclusions The mechanism underlying the piplartine antiplatelet action is not totally clarified. It could be related to the inhibition of cyclooxgenase activity and a decrease in thromboxane A₂ formation, similar to that occurring with aspirin. This and other possible mechanisms require further study.     

Synthesis,Antiplatelet and Vasorelaxing Activities of Xanthone Derivatives

A series of ω‐aminoalkoxylxanthones was synthesized and tested in vitro for their ability to inhibit platelet aggregation and cause vasorelaxing action. Compounds 4 , 5 , 12 , 17 , and 18 showed significant antiplatelet effects on thrombin‐, arachidonic acid (AA)‐, collagen‐, and platelet activating factor (PAF)‐induced washed rabbit platelet aggregation and exhibited inhibition of primary and secondary aggregation induced by adenosine‐5'‐diphosphate (ADP) in human platelet‐rich‐plasma (PRP). Compounds 4 , 17 , and 18 revealed vasorelaxing activities in rat thoracic aorta. We concluded that these compounds may be developed as new antithrombotic agents.     

Antiplatelet action of ilexoside D,a triterpenoid saponin fromIlex pubescens

The anti-platelet activity of ilexoside D isolated from the roots ofIlex pubescens Hook. et Arn. was investigated inin vitro andex vivo models of platelet aggregation induced by ADP, thrombin or collagen in rats.In vitro ilexoside D inhibited more effectively platelet aggregation induced by ADP and thrombin than by collagen as compared with aspirin.Ex vivo ilexoside D also inhibited platelet aggregation induced by ADP and collagen, but not by thrombin, and the inhibitory action of ilexoside D was more effective than that of aspirin. However,in vitro ilexoside D inhibited very poorly the generation of malonyldialdehyde, which is known to be concomitantly released with thromboxane A₂ during platelet aggregation. These results suggest that the anti-platelet activity of ilexoside D may not be responsible for prostaglandin synthesis in platelets.     

Bakkenolide G,a Natural PAF-receptor Antagonist

Because platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) participates in many physiopathological responses, including inflammatory reaction, endotoxic shock, allergic diseases and platelet aggregation, PAF-receptor antagonists are important in the treatment of these diseases. A biologically active compound, bakkenolide G, extracted from the plant Petasites formosanus selectively and concentration-dependently inhibited PAF-induced platelet aggregation and ATP release. The IC50 of bakkenolide G for PAF (2 ng mL^?1)-induced platelet aggregation was 5.6 ± 0.9 μm . Bakkenolide G also concentration-dependently inhibited PAF-induced intracellular signal transductions, including thromboxane B₂ formation, and increased intra-cellular calcium concentration and phosphoinositide breakdown without affecting those caused by thrombin (01 units mL^?1), collagen (10 μg mL^?1), arachidonic acid (100 μm ) and U46619 (1 μm ). Bakkenolide G shifted the concentration-response curves of PAF-induced platelet aggregation parallel to the right; the Schild plot slope and the pA₂ value were 1.31 ± 0.31 and 6.21 ± 0.75, respectively. Moreover, bakkenolide G concentration-dependently competed with [³H]PAF binding to platelets, with an IC50 value of 2.5 ± 0.4 μm . These data strongly indicate that bakkenolide G is a specific PAF-receptor antagonist as an antiplatelet aggregatory agent.     

Antithrombotic effects of Huanglian Jiedu decoction in a rat model of ischaemia-reperfusion-induced cerebral stroke

ContextHuanglian Jiedu Decoction (HLJJD) has a variety of pharmacological activities, such as anti-inflammatory and neuroprotection against ischaemic brain injury.ObjectivesThis ex vivo study explores its antithrombosis activity and inhibition of platelet aggregation.Material and methodsTo study the antithrombosis activity of HLJJD ex vivo, saline, or HLJDD (100, 200, and 500 mg/kg) was treated prophylactically by gavage for 3 days in Wistar rats (n = 4). Based on the rat model of transient middle cerebral artery infarction (MCAO) or normal rats (n = 4), the antithrombotic activity in the normal group and HLJDD subgroups on prothrombin time, thrombus weight, platelet aggregation, and others was evaluated, followed by the antiplatelet aggregation of its main components (n = 4).ResultsThe weight of the thrombus increased significantly at 24 h after MCAO onset. HLJJD did not influence the change of PT, but significantly inhibited thrombosis by 12.5, 20.0, and 20.5% in reducing the dry weight of thrombus, and blocked collagen-induced platelet aggregation by 25.5, 39.0, and 42.7% and adhesion of blood platelet by 17.3, 26.2, and 27.3%. The IC₅₀ value of HLJJD on collagen-induced platelet aggregation was 670 mg/kg. Geniposide only facilitated antiplatelet aggregation induced by collagen, but not AA or ADP. Both baicalin and berberine showed markedly antiplatelet aggregation induced by all activators. The antithrombotic activity of baicalin was relatively higher than that of berberine (35.0–47.8% vs. 20.6–33.5%).ConclusionOur results indicated that HLJDD regulated blood circulation by inhibiting platelet aggregation and thrombosis, which might also extensively contribute to the clinical prevention and treatment of cerebrovascular diseases.     

Antiplatelet Effects of Some Aporphine and Phenanthrene Alkaloids in Rabbits and Man

Two aporphines (boldine and laurolitsine) and five phenanthrene alkaloids (litebamine, secoboldine, N-cyanosecoboldine, N-methylsecoglaucine and N-methylsecopredicentrine) were evaluated in-vitro for their ability to inhibit platelet aggregation. All seven alkaloids inhibited aggregation of rabbit platelets and inhibited the release of ATP induced by arachidonic acid and collagen in rabbit platelets. Those aggregations induced by platelet-activating factor (PAF), thrombin, U46619 and ADP were inhibited by the three N-substituted secoboldine derivatives only. Thromboxane B₂ formation caused by arachidonic acid was also suppressed by these compounds. They did not affect the generation of [³H]inositol monophosphate caused by collagen, PAF and thrombin in the presence of indomethacin. Platelet cyclic AMP level was unaffected by litebamine, but was increased by N-methyl-secoglaucine. Litebamine suppressed the secondary aggregation, but not the primary aggregation, induced by ADP and adrenaline in platelet-rich plasma from man, whereas N-methylsecoglaucine inhibited both primary and secondary aggregation. It is concluded that the antiplatelet effect of these seven aporphine and phenanthrene alkaloids is mainly a result of inhibition of thromboxane A₂ formation; N-methylsecoglaucine has additional antiplatelet activity as a result of increasing the levels of platelet cyclic AMP.     

Antiplatelet aggregation activity of compounds isolated from Guttiferae species in human whole blood

Twenty compounds isolated from Calophyllum inophyllum L., C. inophylloides King, Garcinia opaca King, G. bancana Miq., and G. parvifolia Miq. (Guttiferae) were evaluated for their ability to inhibit platelet aggregation in human whole blood induced by arachidonic acid (AA), collagen, and adenosine diphosphate (ADP). The compounds inhibited platelet aggregation in a dose-dependent manner. Among the compounds tested, 2-(3-methylbut-2-enyl)-1,3,5-trihydroxyxanthone and 2-(3-methylbut-2-enyl)-1,3,5,6- tetrahydroxyxanthone showed strong inhibitory activity on platelet aggregation induced by AA with IC₅₀ values of 115.9 and 113.0?μM, respectively. Rubraxanthone showed inhibitory activity against aggregation caused by the three inducers, and was the most effective antiplatelet compound against collagen-induced platelet aggregation with an IC₅₀ value of 47.0?μM. Macluraxanthone, GB-1a, pyranoamentoflavone, and a neoflavonoid showed selective inhibitory activity on platelet aggregation induced by ADP.     

Effect of 2(1-piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (AP155) on human platelets in vitro

The effect on human platelets of 2-(1-piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (AP155) was tested in vitro by measuring cyclic adenosine monophosphate (cAMP) level, cytosolic Ca⁺⁺, [¹²⁵I]fibrinogen binding as well as aggregation induced by several agonists. AP155 dose-dependently inhibited aggregation both in platelet rich plasma (PRP) and in washed platelets (WP), exerting its maximal power in the presence of collagen, ADP and platelet activating factor (PAF). It specifically inhibited the activity of cAMP high affinity phosphodiesterase (PDE), resulting in a sufficient increase in cAMP levels to activate cAMP-dependent protein kinase. AP155 was able to inhibit aggregation, the increase in cytosolic Ca⁺⁺ induced by thrombin, and fibrinogen binding to ADP or thrombin-stimulated platelets. Thus, this new pyridopyrimidine derivative exerts its antiplatelet activity by increasing cAMP intracellular concentration.     

Mechanism of Action of p-Chlorobiphenyl on the Inhibition of Platelet Aggregation

p-Chlorobiphenyl (1–50 μm ) concentration-dependently inhibited the aggregation and release reaction of rabbit washed platelets induced by arachidonic acid and collagen, but not those induced by platelet-activating factor (PAF), U46619 and thrombin. The IC50 values of p-chlorobiphenyl on the arachidonic acid and collagen-induced platelet aggregation were 2.9 ± 0.5 and 12.8 ± 2.3 μm , respectively. The formation of both platelet thromboxane B₂ and prostaglandin D₂ caused by arachidonic acid was inhibited by p-chlorobiphenyl concentration-dependently. In myo-[³H]inositol-labeled and fura-2-loaded platelets, [³H]inositol monophosphate generation and the rise in intracellular Ca²⁺ stimulated by arachidonic acid were inhibited by p-chlorobiphenyl. In human platelet-rich plasma, p-chlorobiphenyl and indomethacin prevented the secondary aggregation and blocked ATP release from platelets induced by adenosine 5′-diphosphate and adrenaline without affecting the primary aggregation. It is concluded that p-chlorobiphenyl may be a cyclo-oxygenase inhibitor and its antiplatelet action is mainly due to the inhibition of thromboxane formation.     

Antiplatelet Mechanism of 2‐Chloro‐3‐(4‐hexylphenyl)‐amino‐1,4‐naphthoquinone (NQ304), an Antithrombotic Agent

Abstract: The effects of 2‐chloro‐3‐(4‐hexylphenyl)‐amino‐1,4‐naphthoquinone (NQ304), an antithrombotic agent, on aggregation, binding of fibrinogen to glycoprotein IIb/IIIa and intracellular signals were investigated using human platelets. NQ304 inhibited thrombin‐, arachidonic acid‐ and thapsigargin‐induced aggregation of washed human platelets with the IC₅₀ values of 22.2±0.7, 6.5±0.2, and 7.6±0.1 μM, respectively. NQ304 significantly inhibited fluorescein isothiocyanate‐conjugated fibrinogen binding to human platelet surface glycoprotein IIb/IIIa receptor by 75%, but failed to inhibit the fibrinogen binding to purified glycoprotein IIb/IIIa receptor. This result suggests that NQ304 inhibit platelet aggregation by suppression of an intracellular pathway that involves exposure of the glycoprotein IIb/IIIa receptor, rather than by direct inhibition of fibrinogen‐glycoprotein IIb/IIIa binding. NQ304 significantly inhibited thrombin‐induced increase in intracellular Ca²⁺ mobilization at the dose of 30 μM and ATP secretion in a dose‐dependent manner. It also inhibited thrombin‐ and arachidonic acid‐induced thromboxane A₂ formation in human platelet dose‐dependently. In conclusion, the antiplatelet mechanism of NQ304 may be due to the reduction of the thromboxane A₂ formation, inhibition of adenosine triphosphate release and intracellular calcium mobilization.     

NP-184[2-(5-methyl-2-furyl) benzimidazole], a novel orally active antithrombotic agent with dual antiplatelet and anticoagulant activities

The established antiplatelet and anticoagulant agents show beneficial effects in the treatment of thromboembolic diseases; however, these drugs still have considerable limitations. The effects of NP-184, a synthetic compound, on platelet functions, plasma coagulant activity, and mesenteric venule thrombosis in mice were investigated. NP-184 concentration-dependently inhibited the human platelet aggregation induced by collagen, arachidonic acid (AA), and U46619, a thromboxane (TX)A₂ mimic, with IC₅₀ values of 4.5 ± 0.2, 3.9 ± 0.1, and 9.3 ± 0.5 μM, respectively. Moreover, NP-184 concentration-dependently suppressed TXA₂ formations caused by collagen and AA. In exploring effects of NP-184 on enzymes involved in TXA₂ synthesis, we found that NP-184 selectively inhibited TXA₂ synthase activity with an IC₅₀ value of 4.3 ± 0.2 μM. Furthermore, NP-184 produced a right shift of the concentration–response curve of U46619, indicating a competitive antagonism on TXA₂/prostaglandin H₂ receptor. Intriguingly, NP-184 also caused a concentration-dependent prolongation of the activated partial thromboplastin time (aPTT) with no changes in the prothrombin and thrombin time, indicating that it selectively impairs the intrinsic coagulation pathway. Oral administration of NP-184 significantly inhibited thrombus formation of the irradiated mesenteric venules in fluorescein sodium-treated mice without affecting the bleeding time induced by tail transection. However, after oral administration, NP-184 inhibited the ex vivo mouse platelet aggregation triggered by collagen and U46619 and also prolonged aPTT. Taken together, the dual antiplatelet and anticoagulant activities of NP-184 may have therapeutic potential as an oral antithrombotic agent in the treatment of thromboembolic disorders.     

Effects of pentobarbital on pharmacokinetics and pharmacodynamics of a potent fibrinogen receptor antagonist,L-734 217, in dogs

Effects of pentobarbital on pharmacokinetics and pharmacodynamics of L-734 217, a potent fibrinogen receptor antagonist, were studied in male dogs. L-734 217 was given intravenously at 0·01 mg kg⁻¹, in a cross-over fashion, to conscious dogs or to dogs anesthetized with pentobarbital. Plasma concentrations of L-734 217 were measured using a radioimmunoassay and inhibitory effects on ex vivo platelet aggregation induced by ADP or collagen were determined. In pentobarbital-treated dogs, L-734 217 plasma concentrations during the first 3 h collection period were significantly higher than those in the control animals. Corresponding to the increased plasma levels, the mean ex vivo inhibitory effects on ADP- or collagen-induced platelet aggregation in dogs under anesthesia appeared greater than in those without the anesthetic treatment. Pharmacokinetic analysis revealed a modest, but significant (up to 40%) elevation in the area under the plasma concentration–time curve during 6 h of the drug administration, and a reduction in L-734 217 plasma clearance and volumes of distribution, in the anesthetized dogs. Analysis of pharmacodynamic data indicated that the EC₅₀ and the Hill coefficient of the platelet aggregation response–plasma concentration curve were not altered by pentobarbital treatment. The results are in agreement with the findings that the administration of pentobarbital alone (in the absence of L-734 217) did not affect appreciably the ex vivo platelet aggregatory responses. In a separate group of dogs, L-734 217 was found to be metabolically stable, and was eliminated unchanged renally (64±4%) and hepatically (32±6%). In addition, L-734 217 did not bind substantially to canine plasma proteins or blood cellular components. It is possible that alterations of regional hemodynamics, reportedly mediated by pentobarbital, contributed to changes observed in the present study. That is, alterations occurred in L-734 217 elimination and distribution processes which resulted in an increase in drug plasma levels. Since pentobarbital anesthesia influenced only the pharmacokinetics, and not the pharmacodynamics, of L-734 217, the apparent increases in the inhibition of platelet aggregation responses observed following L-734 217 administration to the anesthetized dogs were probably sequential effects of the pharmacokinetic interactions. © 1997 John Wiley & Sons, Ltd.     

Inhibition of platelet aggregation by 2-(p-chlorophenyl)-4-thiazoleacrylic acid (Wy-23,049)--comparison with acetylsalicylic acid

2-(p-Chlorophenyl)-4-thiazoleacrylic acid (Wy-23,049) inhibited the first phase of adenosine diphosphate (ADP) and epinephrine-induced platelet aggregation, while acetylsalicylic acid (ASA) had little effect on the first but effectively inhibited the second phase. ASA was more effective than Wy-23,049 in inhibiting collagen-induced platelet aggregation. An ex vivo guinea-pig experiment demonstrated that Wy-23,049 inhibited the first phase and prevented the appearance of the second phase of ADP-induced platelet aggregation, while ASA inhibited the second phase. Oral administration of Wy-23,049 to rats was much more effective than ASA in protecting the animal against ADP-induced platelet loss. At an oral dose of 40mg/kg, Wy-23,049 prolonged the Lee-White clotting time in rats; ASA did not prolong it.     

Inhibition of rat platelet aggregation by a Prudhoe Bay crude oil and its aliphatic,aromatic, and heterocyclic fractions

Wasjed platelets isolated from rats 24 hr after oral treatment with a Prudhoe Bay crude oil (PBCO) showed a substantial inhibition of aggregation induced by ADP, arachidonic acid, or epinephrine. In vitro addition of a dimethyl sulfoxide extract of PBCO or its aliphatic, aromatic, or heterocyclic fractions to washed platelets also resulted in an inhibition of aggregation. ADP release was inhibited in platelets to which an extract of PBCO or its fractions were added in vitro or in platelets isolated from rats treated in vivo with PBCO. Thromboxane B₂ release was increased in platelets isolated from rats intubated with PBCO or in platelets to which a dimethyl sulfoxide extract of the aromatic or heterocyclic fraction was added. However, thromboxane B₂ release was inhibited in platelets to which PBCO or the aliphatic fraction extracts were added. The results indicate that PBCO inhibits platelet aggregation presumably by bringing about alterations in the platelet plasma membrane. Inhibition of ADP release could contribute to the inhibition of aggregation but thromboxane B₂ is believed not to play a significant role.     

In Vitro Antiplatelet Activity of Flavonoids from Leuzea Carthamoides

Plants and their secondary metabolites, including flavonoids, exhibit a wide range of biological effects. Consequently, natural substances are receiving an increased attention in medicinal research. Owing to these facts, in vitro antiplatelet activity of ethanol summary extract and four flavonoids from Leuzea carthamoides was determined in human platelet-rich plasma. Arachidonic acid (AA), adenosine diphosphate (ADP), collagen (COL), and thrombin were used as agonists of platelet aggregation. The summary extract showed a significant inhibition of the aggregation induced by COL and ADP. Of the tested flavonoids, eriodictyol (1) and patuletin (2) influenced COL- and AA-induced aggregation. Their IC₅₀ values are presented. Flavonoid glycosides eriodictyol-7-β-glucopyranoside (3) and 6-hydroxykaempferol-7-O-(6″-O-acetyl-β-D[small cap]-glucopyranoside) (4) were found to be weak antiplatelet agents. These results confirmed the fact that glucosylation decreases the antiplatelet activity. Quantitative composition of tested flavonoids in L. carthamoides extract was also determined. Though two of the tested flavonoids inhibited platelet aggregation, further evaluation of L. carthamoides, in order to discover other antiplatelet active compounds and possible adverse health effects, is needed.     

Nα-乙酰-精氨酰-甘氨酰-天冬氨酰-对甲氧基苯乙胺对血小板聚集的抑制

N^α-乙酰-精氨酰-甘氨酰-天冬氨酰-对甲氧基苯乙胺(W2002)是精-甘-天冬氨酸(Arg-Gly-Asp)肽类血小板聚集抑制剂. 为探讨其抗血小板聚集的活性, 分别用比浊法和血小板计数的方法测定二磷酸腺苷(ADP)及高剪切速率诱导的血小板聚集,并用放射性配体分析法测定血小板表面结合［¹²⁵I］纤维蛋白原(FGN)的含量, 以了解W2002竞争性抑制［¹²⁵I］FGN与血小板糖蛋白(GP)Ⅱb/Ⅱa结合的生物活性. 结果显示 : W2002有明显的抑制ADP诱导血小板聚集的活性, 除最低终浓度(9 μmol·L^-1)外, 其余各浓度点(270, 135, 45 μmol·L^-1)与生理盐水对照组比较差异均非常显著; 其对抗高剪切速率诱导的血小板聚集也有明确的量-效关系; 抑制［¹²⁵I］FGN与血小板结合的IC₅₀值为 (41.5±2.9)μmol·L^-1, 在老年人和青年人群中比较无明显差异. 研究提示W2002通过抑制FGN与血小板GPⅡb/Ⅲa的结合而发挥作用.     

钩藤碱对家兔血小板聚集及胞浆游离钙离子浓度的影响

目的 研究钩藤碱(Rhy)对兔血小板细胞内游离钙离子浓度及血小板聚集的影响.方法 56只雄性家兔的血样随机分为正常对照组,阿司匹林0.85,1.69和2.78 mmol·L-1组,Rhy 0.33,0.65和1.30 mmol·L-1组.Born法测定血小板聚集率,双波长Fura-2荧光分光光度法测定血小板胞浆游离钙离...     

Synthesis and antiaggregant activity of 2-cycloalkylamino-5-thienyl- and -5-furyl-6<Emphasis Type="Italic">H</Emphasis>-1,3,4-thiadiazines

A series of new 5-(thienyl-2)-, 5-(furyl-2)-, and 5-(thienyl-3)-1,3,4-thiadiazine derivatives have been synthesized using methods based on the cyclocondensation of α-bromoacetylthiophenes or α-bromo-2-acetylfurans with 4-substituted thiosemicarbazides. The effects of the synthesized compounds on human platelet aggregation in vitro and on rabbit platelet aggregation ex vivo have been studied. The most active 5-(thienyl-2)-1,3,4-thiadiazines inhibit human platelet aggregation induced by ADP and arachidonic acid in a broad concentration range. These compounds have good potential as emergency drugs for the treatment and prophylaxis of infarction and stroke.     

Synthesis of thioether derivatives of quinazoline-4-one-2-thione and evaluation of their antiplatelet aggregation activity

A series of 2-(arylmethylthio)-3-phenylquinazolin-4-one derivatives have been synthesized and their antiplatelet aggregation activities were assessed against ADP and arachidonic acid-induced platelet aggregation in human plasma. Among the tested thioethers, derivative 2, 3, 5 and 16 were the most potent compounds with satisfactory IC₅₀ for inhibition of platelet aggregation induced by ADP. Analysis of global physicochemical parameters shows some correlations between activities and molecular volume and also surface area of the studied derivatives.