2-Substituted 4-, 5-, and 6-[(1E)-3-oxo-3-phenylprop-1-en-1-yl]pyridazin-3(2H)-ones and 2-substituted 4,5-bis[(1E)-3-oxo-3-phenylprop-1-en-1-yl]pyridazin-3(2H)-ones as potent platelet aggregation inhibitors: design, synthesis, and SAR studies.

A set of regioisomeric 2-substituted pyridazin-3(2H)-ones containing a 3-oxo-3-phenylprop-1-en-1-yl fragment at either position 4, 5 or 6 and 2-substituted pyridazin-3(2H)-ones containing the same fragment both at positions 4 and 5 have been synthesized and evaluated as antiplatelet agents. The study allows the identification of a new highly potent platelet aggregation inhibitor (4c).

Design, synthesis, and structure-activity relationships of a novel series of 5-alkylidenepyridazin-3(2H)-ones with a non-cAMP-based antiplatelet activity.

5-alkylidenepyridazin-3-ones with four points of diversity (R2, R6, X, Y) have been synthesized and evaluated as platelet aggregation inhibitors. Several derivatives eliciting antiplatelet activity in the low micromolar range (e.g., 14e, 14k, 14p, 14v, IC50 congruent with 1 microM) were identified. Structure-activity relationships studies on these compounds revealed the key molecular determinants of this new family of antiplatelet agents: (a) two ester groups in the alkoxy moieties; (b) lipophilic substituents at the N2 position of the pyridazin-3-one. The preliminary results of a pharmacological study aimed at determining the mechanism of action of a set of representative compounds revealed that, unlike other pyridazinones, the documented antiplatelet effect is not a consequence of a PDE-III inhibitory activity.

(-)-Trans-epsilon-viniferin, a polyphenol present in wines, is an inhibitor of noradrenaline and 5-hydroxytryptamine uptake and of monoamine oxidase activity.

(-)-Trans-epsilon-viniferin (epsilon-viniferin, 5-200 microM), a dimer of resveratrol, concentration-dependently inhibited the uptake of [3H]noradrenaline and [3H]5-HT by synaptosomes from rat brain (being slightly but significantly more selective against [3H]noradrenaline) and the uptake of [3H]5-HT by human platelets. On the other hand, epsilon-viniferin (5-200 microM) concentration-dependently inhibited the enzymatic activity of commercial (human recombinant) monoamine oxidase (MAO) isoform (MAO-A and MAO-B) activity, being slightly but significantly more selective against MAO-B than against MAO-A. Taking into account that the principal groups of drugs used to treat major depression are noradrenaline/5-HT uptake or MAO inhibitors, under the assumption that epsilon-viniferin exhibits a similar behaviour in humans in vivo, our results suggest that this natural polyphenol may be of value as a structural template for the design and development of new antidepressant drugs with two important biochemical activities combined in the same chemical structure: noradrenaline/5-HT uptake and MAO inhibitory activity.

Inhibitory effects of cis- and trans-resveratrol on noradrenaline and 5-hydroxytryptamine uptake and on monoamine oxidase activity.

This study investigated for the first time the potential effects of cis- and trans-resveratrol (c-RESV and t-RESV) on noradrenaline (NA) and 5-hydroxytryptamine (5-HT) uptake by synaptosomes from rat brain, on 5-HT uptake by human platelets, and on monoamine oxidase (MAO) isoform activity. Both c-RESV and t-RESV (5-200 microM) concentration-dependently inhibited the uptake of [3H]NA and [3H]5-HT by synaptosomes from rat brain and the uptake of [3H]5-HT by human platelets. In both experimental models, t-RESV was slightly more efficient than c-RESV. Furthermore, in synaptosomes from rat brain, the RESV isomers were less selective against [3H]5-HT uptake than the reference drug fluoxetine (0.1-30 microM). On the other hand, both c-RESV and t-RESV (5-200 microM) concentration-dependently inhibited the enzymatic activity of commercial (human recombinant) MAO isoform (MAO-A and MAO-B) activity, c-RESV being slightly less effective than t-RESV. In addition, both RESV isomers were slight but significantly more selective against MAO-A than against MAO-B. Since the principal groups of drugs used in the treatment of depressive disorders are NA/5-HT uptake or MAO inhibitors, under the assumption that the RESV isomers exhibit a similar behaviour in humans in vivo, our results suggest that these natural polyphenols may be of value as structural templates for the design and development of new antidepressant drugs with two important biochemical activities combined in the same chemical structure: NA/5-HT uptake and MAO inhibitory activity.

Differential regulation of platelet aggregation and aminophospholipid exposure by calpain.

Aggregation, exposure of procoagulant phospholipids and shedding of microparticles are platelet responses that depend on activating conditions. To determine how these different responses are interconnected, we simultaneously measured fibrinogen (Fg) binding and aminophospholipid exposure on activated platelets by means of flow cytometry. Low calcium ionophore (A23187) concentrations induced Fg binding but not annexin V binding. In contrast, high A23187 concentrations induced annexin V binding but not Fg binding. Collagen, both alone and in the presence of thrombin, induced both Fg and annexin V binding. Dual labelling was found on 38 +/- 9% of platelets stimulated by thrombin plus collagen. The regulatory role of calpain in these platelet functions was investigated. When calpain was partially inhibited by 2 microg/ml calpeptin, Fg binding still occurred but aminophospholipid exposure was limited. By contrast, complete inhibition of calpain by 100 microg/ml calpeptin or E64d decreased Fg binding but enhanced aminophospholipid exposure. In these latter conditions, cytosolic calcium-extruding systems were inhibited. The results suggest that (i) conditions that favour aminophospholipid exposure tend to decrease the aggregation process and (ii) calpain determines the switch to either aggregation or aminophospholipid exposure by controlling intracellular calcium.

Design, synthesis, and vasorelaxant and platelet antiaggregatory activities of coumarin-resveratrol hybrids.

We have synthesized the coumarin-resveratrol hybrid 4 and its dimethoxy derivative 3 by a very direct synthetic route involving a Pechmann procedure. Compound 4 has also been synthesized by an alternative route (Perkin), which also allowed the synthesis of compounds 9-13. In addition, we have evaluated the potential vasorelaxant activity of the new compounds in endothelium-containing rat aorta rings pre-contracted with noradrenaline, as well as the inhibitory effects on platelet aggregation induced by thrombin in washed human platelets. The compounds reported here relaxed vascular smooth muscle and inhibited platelet aggregation with a profile similar to that of trans-resveratrol (t-RESV) and, in some cases, showed activity higher than that of the natural compound. This is the case for compound 13, which has a vasorelaxant activity that is twice as high as that of t-resveratrol and a platelet antiaggregant activity that is six times higher. These results suggest that these novel compounds may have potential as structural templates for the design and subsequent development of new vasodilatory and platelet antiaggregatory drugs.

Pyridazines part 41: synthesis, antiplatelet activity and SAR of 2,4,6-substituted 5-(3-oxo-3-phenylprop-1-en-1-yl)- or 5-(3-phenylprop-2-enoyl)pyridazin-3(2H)-ones.

As part of the optimization process of the lead compound I a focussed library of diversely substituted pyridazin-3(2H)-ones containing a 3-oxo-3-phenylprop-1-en-1-yl or 3-phenylprop-2-enoyl fragment at position 5 has been obtained and evaluated as antiplatelet agents. The structural modification at positions 2, 6 and 4 of the heterocyclic moiety allowed us to obtain preliminary information on the structure-activity relationship in this family.

Pyridazines. Part 28: 5-alkylidene-6-phenyl-3(2H)-pyridazinones, a new family of platelet aggregation inhibitors.

The synthesis and anti-platelet activity of several 5-alkylidene-6-phenyl-3(2H)-pyridazinones are described. The most active compounds are those that contain oxygenated functions (COOR, COMe) on the alkylidene fragment (6a, 6b and 6c).

Pyridazines. Part 36: Synthesis and antiplatelet activity of 5-substituted-6-phenyl-3(2H)-pyridazinones.

A convenient and efficient palladium-catalysed retro-ene-assisted method has been developed to prepare a series of 5-substituted-6-phenyl-3(2H)-pyridazinones as potential antiplatelet drugs. The most active compounds were those that contain a 3-phenyl-3-oxo-propenyl fragment or a phenylthio group at position 5 of the heterocyclic ring.

Pyridazines. Part XXIX: synthesis and platelet aggregation inhibition activity of 5-substituted-6-phenyl-3(2H)-pyridazinones. Novel aspects of their biological actions.

A series of 6-phenyl-3(2H)-pyridazinones with a diverse range of substituents in the 5-position have been prepared and evaluated in the search for new antiplatelet agents. A significant dependence of the substituent on the inhibitory effect has been observed. The pharmacological study of these compounds confirms that modification of the chemical group at position 5 of the 6-phenyl-3(2H)-pyridazinone system influences both variations in the antiplatelet activity and the mechanism of action.

Pyridazines. Part 31: synthesis and antiplatelet activity of 4,5-disubstituted-6-phenyl-3(2H)-pyridazinones.

This paper describes the synthesis and the antiplatelet activity of a series of 4,5-disubstituted-6-phenyl-3(2H)-pyridazinones. Some of these compounds show a dose-dependent activity and were found to be more active than their 5-substituted analogues.