Antiplatelet effect of 2-(diethylamino)-7-hydroxychromone

Synthesis, in vitro antiplatelet activity and molecular modelling studies of 10-substituted 2-(1-piperazinyl)pyrimido[1,2-a]benzimidazol-4(10H)-ones

The multistep preparation of the new 10-substituted 2-(1-piperazinyl)pyrimido[1,2-a]benzimidazol-4(10H)-ones 6a-o, and of the two isomers 10-ethyl-2-(diethylamino)pyrimido[1,2-a]benzimidazol-4(10H)-one 6p and 10-ethyl-4-(diethylamino)pyrimido[1,2-a]benzimidazol-2(10H)-one 13, as well as the in vitro evaluation of their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP, collagen or the Ca(2+) ionophore A23187 were here described. Nine out of fifteen 2-(1-piperazinyl)derivatives (6g-o) showed good inhibitory properties towards all the platelet aggregation agonists used. Moreover, a molecular modelling study has been performed on two of the best compounds of this series (6i and 6o) to confirm in silico their interactions with the catalytic site of human platelet PDE3, using the X-ray data of the PDE3B isoform in complex with an inhibitor.

Synthesis and in vitro antiplatelet activity of new 4-(1-piperazinyl)coumarin derivatives. Human platelet phosphodiesterase 3 inhibitory properties of the two most effective compounds described and molecular modeling study on their interactions with phosphodiesterase 3A catalytic site

The synthesis and in vitro antiplatelet activity significant data of coumarin derivatives 5i-x and quinolin-2(1H)-one derivatives 22a,b, as well as the corresponding structure-activity relationships are described. The recently reported 8-methyl-4-(1-piperazinyl)-7-(3-pyridylmethoxy)coumarin 5f and its potent 7-(2-morpholinoethoxy)-substituted new analogue 5u were notably more effective inhibitors of pure human platelet PDE3 than milrinone and cilostazol: these data were related, through a molecular modeling study, with the molecular interactions of the four compounds with the human PDE3A catalytic site.

Analysis of anti-PDE3 activity of 2-morpholinochromone derivatives reveals multiple mechanisms of anti-platelet activity

A series of synthetic 2-morpholinochromones have been evaluated as inhibitors of platelet phosphodiesterase, PDE3A. While previous assertions about the anti-PDE3 activity of this class have been confirmed, in some cases the reported anti-platelet activities clearly derive from a non-PDE3 regulated mechanism. The potential utility of 2-morpholinochromones either as PDE3 inhibitors and/or anti-thrombotic agents thus remains only poorly examined.

Synthesis and in vitro inhibitory activity on human platelet aggregation of novel properly substituted 4-(1-piperazinyl)coumarins

Pursuing our chemical and biological studies in this field, we described the multistep preparation of the new 5-, 6-, or 7-alkoxy and 7-alkoxy-8-methyl substituted 4-(1-piperazinyl)coumarins 5d-v, as well as the in vitro evaluation of their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP, collagen or the Ca(2+) ionophore A23187. Compounds 5h-j,p,r-u showed notably high activity towards all the platelet aggregation inducers used, and the most active one, 8-methyl-4-(1-piperazinyl)-7-(3-pyridylmethoxy)coumarin (5t), proved to be a potent in vitro antiplatelet agent.

Mechanisms involved in the antiplatelet activity of 8-methyl-4-(1-piperazinyl)-7-(3-pyridinylmethoxy)-2H-1-benzopyran-2-one (RC414)

The effect on human platelets of 8-methyl-4-(1-piperazinyl)-7-(3-pyridinylmethoxy)-2H-1-benzopyran-2-one (RC414) was tested in vitro by measuring aggregation induced by several agonists, cAMP and cGMP levels, cAMP phosphodiesterase and PKC activities and [Ca2+]i. The RC414 effect on nitric oxide production was also evaluated. RC414 in a dose-dependent manner inhibited aggregation both in platelet rich plasma and in washed platelets. It was particularly effective in platelets challenged by collagen, ADP and thrombin: IC50 values are 0.51 +/- 0.12 microM, 0.98 +/- 0.36 microM and 1.00 +/- 0.15 microM, respectively. RC414 increased cAMP levels, through the specific inhibition of the cAMP high affinity phosphodiesterase (IC50 = 1.73 +/- 0.35 microM). RC414 reduced [Ca2+]i transients and PKC activation induced by thrombin. In addition RC414 was able to increase nitric oxide formation involving the stimulation of constitutive nitric oxide synthase enzyme. In conclusion, RC414 exerts its powerful anti-platelet activity by increasing cAMP intracellular levels and nitric oxide formation.

Coumarin, chromone, and 4(3H)-pyrimidinone novel bicyclic and tricyclic derivatives as antiplatelet agents: synthesis, biological evaluation, and comparative molecular field analysis

As a further part of our chemical and biological studies in this field, we describe the multistep preparations of the properly substituted 2-(1-piperazinyl)chromone 1b, 4-(1-piperazinyl)coumarins 5c-h, their linear benzo-fused analogues 4a,b and 8a,b, bicyclic (15e-g) and tricyclic (15h,i) fused derivatives of 6-(1-piperazinyl)pyrimidin-4(3H)-one, and of the 4H-pyrido[1,2-a]pyrimidine derivatives 9b,c. The in vitro evaluation of their inhibitory properties towards human platelet aggregation induced in platelet-rich plasma by ADP, collagen, or the Ca (2+)ionophore A23187 showed the high activity of compounds 5d-g and 15f,g,i, among which the coumarins 5g and 5d proved to be, in that order, the most effective in vitro antiplatelet agents until now synthesized by us. Thus, in order to consider also the 4-aminocoumarin structural class, we developed a new statistically significant 3-D QSAR model, more general than the one previously obtained, through a further CoMFA study based on the antiplatelet activity data and molecular steric and electrostatic potentials of both the previously studied and herein described compounds.

Synthesis, antiplatelet activity and comparative molecular field analysis of substituted 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones, their congeners and isosteric analogues

2-(1-Piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (5a) is a recently described in vitro inhibitor of human platelet aggregation which specifically inhibits the activity of high affinity cAMP phosphodiesterase. A number of substitution derivatives, isosteres, and analogues of 5a were now synthesized and tested in vitro for their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP, collagen, or the Ca2+ ionophore A23187. Among the most effective compounds, the 6-methyl, 8-methyl and 6,8-dimethyl derivatives of 5a resulted nearly as active as the lead when platelet aggregation was induced by ADP or A23187, but less active when collagen was the inducer. On the basis of present results and those previously obtained by us in this and 2-aminochromone structural fields, we have developed a statistically significant 3-D QSAR model, using comparative molecular field analysis (CoMFA), describing the variation of the antiplatelet activity in terms of molecular steric and electrostatic potential changes.

N,N-dialkylaminosubstituted chromones and isoxazoles as potential anti-inflammatory agents

The ability of some N,N-dialkylaminosubstituted chromones and isoxazoles to inhibit the protein kinase C (PKC) dependent signal transduction pathway was tested. As a cellular model, human neutrophils stimulated with either phorbol myristate acetate (PMA) or formylmethionine-leucine-phenylalanine (f-MLF) were used. The efficiency of the compounds was established by their capacity to reduce the O2- production by activated human neutrophils. Compounds carrying a 3-bis(2-methoxyethyl)amino group, a substituent found active in previously tested tricyclic compounds, do not show significant anti-PKC activity in this study. On the other hand, substitution with a 1-piperidinyl group leads all tested compounds to a high biological activity against stimulated neutrophils.

Mechanism of action of two new pyrimidoquinoline and isoquinoline derivatives in human platelets

In the present study the "in vitro" influence of 3-(1-piperazinyl)-1H-pyrimido[1,2-a]quinolin-1-one (AQ11) and 2-(piperazinyl)-4H-pyrimido[2,1-a]isoquinolin-4-one (IQ3b) on human platelet aggregation, cAMP elevation, cytosolic calcium and fibrinogen binding has been investigated. Both drugs inhibited platelet aggregation in a concentration-dependent manner. In PRP AQ11 was slightly more active than IQ3b when aggregation was induced by ADP, collagen, A23187 or PMA, whereas in washed platelets challenged by thrombin, IQ3b was more effective than AQ11. Both compounds produced increase in cAMP intracellular level being the effect potentiated by the adenylate cyclase activator iloprost and IQ3b was more powerful than AQ11. Moreover IQ3b was more effective in inhibiting cAMP in high affinity phosphodiesterase (IC50 values: IQ3b 11 +/- 5 microM; AQ11 43 +/- 8 microM) and calcium elevation (IC50 values: IQ3b 9 +/- 4 microM; AQ11 32 +/- 6 microM). These compounds also inhibited fibrinogen binding in platelets challenged by ADP or thrombin. The results suggest that these new potent agents inhibit platelet phosphodiesterase activity causing an elevation in cAMP levels sufficient to inhibit calcium rise and fibrinogen binding. This mechanism can be responsible for the ability of the compounds to prevent platelet aggregation.

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]pyrimi din-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.