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Rationale: Human cardiac mesenchymal cells (CMSCs) are a therapeutically relevant primary cell population. Diabetes mellitus compromises CMSC function as consequence of metabolic alterations and incorporation of stable epigenetic changes. Objective: To investigate the role of α-ketoglutarate (αKG) in the epimetabolic control of DNA demethylation in CMSCs. Methods and Results: Quantitative global analysis, methylated and hydroxymethylated DNA sequencing, and gene-specific GC methylation detection revealed an accumulation of 5-methylcytosine, 5-hydroxymethylcytosine, and 5-formylcytosine in the genomic DNA of human CMSCs isolated from diabetic donors. Whole heart genomic DNA analysis revealed iterative oxidative cytosine modification accumulation in mice exposed to high-fat diet (HFD), injected with streptozotocin, or both in combination (streptozotocin/HFD). In this context, untargeted and targeted metabolomics indicated an intracellular reduction of αKG synthesis in diabetic CMSCs and in the whole heart of HFD mice. This observation was paralleled by a compromised TDG (thymine DNA glycosylase) and TET1 (ten–eleven translocation protein 1) association and function with TET1 relocating out of the nucleus. Molecular dynamics and mutational analyses showed that αKG binds TDG on Arg275 providing an enzymatic allosteric activation. As a consequence, the enzyme significantly increased its capacity to remove G/T nucleotide mismatches or 5-formylcytosine. Accordingly, an exogenous source of αKG restored the DNA demethylation cycle by promoting TDG function, TET1 nuclear localization, and TET/TDG association. TDG inactivation by CRISPR/Cas9 knockout or TET/TDG siRNA knockdown induced 5-formylcytosine accumulation, thus partially mimicking the diabetic epigenetic landscape in cells of nondiabetic origin. The novel compound (S)-2-[(2,6-dichlorobenzoyl)amino]succinic acid (AA6), identified as an inhibitor of αKG dehydrogenase, increased the αKG level in diabetic CMSCs and in the heart of HFD and streptozotocin mice eliciting, in HFD, DNA demethylation, glucose uptake, and insulin response. Conclusions: Restoring the epimetabolic control of DNA demethylation cycle promises beneficial effects on cells compromised by environmental metabolic changes.

A number of new nitric oxide (NO)-precursors were synthesized by grafting nitrate-containing moieties on the structures of the benzyloxy isonipecotanilide derivatives 1 and 2 already reported as moderately potent antiplatelet agents. Various nitrooxy (ONO2)-alkyl side chains were covalently linked to the piperidine nitrogen of the parent compounds through carbamate and amide linkage, and the synthesis of a benzyl nitrate analog (15) of compound 1 was also achieved. The in vitro vasodilatory activities, as well as platelet anti-aggregatory effects, of the newly synthesized organic nitrates were assessed. The (ONO2)methyl carbamate-based derivative 5a and the benzyl nitrate analog 15, which on the other hand retain activity as inhibitors of ADP-induced platelet aggregation, exhibited strong NO-mediated vasodilatory effects on pre-contracted rat aorta strips, with EC50 values in the low nanomolar range (13 and 29 nM, respectively). Experiments carried out with the selectively inhibited soluble guanylate cyclase (sGC), which is the key enzyme of the NO-mediated pathway leading to vascular smooth muscle relaxation, confirmed the involvement of NO in the observed vasodilation. The nitrate derivatives proved to be stable in acidic aqueous solution and at pH 7.4. In human serum, unlike 5a, which showed not to undergo enzyme-catalyzed decomposition, the other tested (ONO2)-alkyl carbamate-based compounds (5b and 5e) and benzyl nitrate 15 underwent a faster degradation. However, their decomposition rates in serum were quite slow (t½ > 2.6 h), which suggests that nitrate moiety is poorly metabolized in blood plasma and that much of the in vitro anti-platelet activity has to be attributed to the intact (ONO2)-containing molecules.

A new series of bisphosphonates bearing either the nitrogen-containing NO-donor furoxan (1,2,5-oxadiazole 2-oxide) system or the related furazan (1,2,5-oxadiazole) in lateral chain has been developed. pKa values and affinity for hydroxyapatite were determined for all the compounds. The products were able to inhibit osteoclastogenesis on RAW 246.7 cells at 10 μM concentration. The most active compounds were further assayed on human PBMC cells and on rat microsomes. Unlike most nitrogen-containing bisphosphonates which target farnesyl pyrophosphate synthase, experimental and theoretical investigations suggest that the activity of our derivatives may be related to different mechanisms. The furoxan derivatives were also tested for their ability to relax rat aorta strips in view of their potential NO-dependent vasodilator properties.

A series of (nitrooxyacyloxy)methyl esters of aspirin were synthesized and evaluated as new NO-donor aspirins. Different amounts of aspirin were released in serum from these products according to the nature of nitrooxyacyloxy moiety present. In the aromatic series, there is a rather good linear correlation between the amount of aspirin released and the potencies of the products in inhibiting platelet aggregation induced by collagen. Both the native compounds and the related nitrooxy-substituted acid metabolites were able to relax rat aorta strips precontracted with phenylephrine, in keeping with a NO-induced activation of the sGC as a mechanism that underlies the vasodilator effect. The products here described are new improved examples of NO-donor aspirins containing nitrooxy groups. They could represent an alternative to the use of aspirin in a variety of clinical applications.

This study proposes an alternative technique to prevent heat degradation induced by classic procedures of bioactive compound extraction, comparing classical maceration/decoction in hot water of polyphenols from Mango (Mangifera indica L.) (MI) with ultrasound-assisted extraction (UAE) in a water solution of β-cyclodextrin (β-CD) at room temperature and testing their biological activity on TNFα-induced endothelial dysfunction. Both extracts counteracted TNFα effects on EAhy926 cells, down-modulating interleukin-6, interleukin-8, cyclooxygenase-2 and intracellular adhesion molecule-1, while increasing endothelial nitric oxide synthase levels. β-CD extract showed higher efficacy in improving endothelial function. These effects were abolished after pre-treatment with the oestrogen receptor inhibitor ICI1182,780. Moreover, the β-CD extract induced Akt activation and completely abolished the TNFα-induced p38MAPK phosphorylation. UAE and β-CD encapsulation provide an efficient extraction protocol that increases polyphenol bioavailability. Polyphenols from MI play a protective role on endothelial cells and may be further considered as oestrogen-like molecules with vascular protective properties.

The synthesis and study of the antioxidant and vasodilator properties of a new class of phenols able to release nitric oxide are described. The products were designed through a symbiotic approach using selected phenols and selected nitrooxy and furoxan NO-donors as reference models. The antioxidant activities of the hybrid products were assessed by detecting the 2-thiobarbituric acid reactive substances (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids present in microsomial membranes of rat hepatocytes. The vasodilator activity was assessed on rat aortic strips precontracted with phenylephrine. Some of the products (13, 35, 37, 60-62, 64) behave principally as vasodilators and others as antioxidants (24, 32, 72), and the two properties are relatively balanced in 19, 41, and 68. Further in vivo studies should clarify whether some of these products may become preclinical candidates for the treatment of cardiovascular disease underpinned by atheroma.

Synthesis and pharmacological characterisation of a series of products obtained by coupling the H 3 -antagonist SKF 91486 through appropriate spacers with the NO-donor 3-phenylfuroxan-4-yloxy and 3-benzenesulfonylfuroxan-4-yloxy moieties, as well as with the corresponding furazan substructures, devoid of NO-donating properties, are reported. All the products were tested for their H 3 -antagonistic and H 2 -agonistic properties on electrically-stimulated guinea-pig ileum segments and guinea-pig papillary muscle, respectively. The whole series of compounds displayed good H 3 -antagonist behaviour and feeble partial H 2 -agonist activity. Among furoxan derivatives, the benzenesulfonyl hybrid 28 , a good NO-donor, triggered a dual NO-dependent muscle relaxation and H 3 -antagonistic effect on guinea-pig intestine.

The syntheses of almost all N-heterocycles have now been successfully performed under microwave irradiation and have provided significant improvements in the reaction time and efficiency. The peculiar properties of dielectric heating give it the ability to strongly promote cyclocondensation, cycloaddition and selective N-heterocycle functionalisation and it has, therefore, very much caught the attention of the medicinal chemistry community. In this work, we present an overview of recent literature and technical advances in this research field with the aim of providing insight into the applications of microwave-assisted synthesis in the preparation of the main drug categories that contain N-heterocycle scaffolds.

Pyroptosis is a caspase-1-dependent pro-inflammatory form of programmed cell death implicated in the pathogenesis of autoinflammatory diseases as well as in disorders characterized by excessive cell death and inflammation. Activation of NLRP3 inflammasome is a key event in the pyroptotic cascade. In this study, we describe the synthesis and chemical tuning of α,β-unsaturated electrophilic warheads toward the development of antipyroptotic compounds. Their pharmacological evaluation and structure-activity relationships are also described. Compound 9 was selected as a model of this series, and it proved to be a reactive Michael acceptor, irreversibly trapping thiol nucleophiles, which prevented both ATP- and nigericin-triggered pyroptosis of human THP-1 cells in a time- and concentration-dependent manner. Moreover, 9 and other structurally related compounds, inhibited caspase-1 and NLRP3 ATPase activities. Our findings can contribute to the development of covalent, multitarget antipyroptotic compounds targeting molecular components of the NLRP3 inflammasome regulatory pathway.

New anti-Helicobacter pylori (H. pylori) agents endowed with H2-antagonists properties were obtained by combining the lamtidine derived pharmacophoric group with the antibiotic calvatic acid. All the compounds were tested for their irreversible H2-antagonist properties and for their ability to inhibit 20 H. pylori strains, two of them metronidazole resistant. The most active derivative (compound 4) displayed antimicrobial activity similar to metronidazole.

Purpose. Model compounds containing NO-donor furoxan moieties at the 3-positioned basic lateral chain of 1, a 1,4-dihydropyridine related to nicardipine, were synthesized in order to study their vasodilating activity as well as their basic and lipophilic behaviour.

The synthesis and in vitro vasodilating properties of hybrid compounds in which furoxan (1,2,5-oxadiazole 2-oxide) moieties, endowed with diAerent NO-donor properties, were substituted for the nitroxy function of Nicorandil are reported. The corresponding cyanoguanidine analogues are also considered. This approach has led to a series of vasorelaxing compounds devoid of aAnity for KATP channels, whose activity is prevalently due to their ability to activate sGC, at the concentrations of the experi- ments. Related furazan (1,2,5-oxadiazole) derivatives, unable to release nitric oxide were also prepared and studied for control. The amide analogues of Nicorandil display feeble vasorelaxing action not involving the activation of K + channels, while in the guani- dine analogues, this mechanism seems to underlie this action. # 2000 Elsevier Science Ltd. All rights reserved.

Purpose. A series of derivatives having a propranolol-like moiety linked to NO-donor furoxan substructures were synthesized. The main objective of this investigation was to obtain agents with mixed NO-dependent vasodilating and β-blocking activities.

Synthesis and structural characterization of some ring-open analogues of Prazosin containing either the guanidine substructure or urea-equivalent groups are described. The opening of the pyrimidine ring in Prazosin is very important as far as the affinity for α1-adrenoceptor is concerned. The pA2 values of the ring-open derivatives are 104–105 fold lower than that of the parent. It is probable that the affinity decrease principally reflects a negative influence of the conformational factors in the interaction with the α1-receptor. The derivative 5 containing the guanidine moiety, charged at physiological pH, is as active as the other derivatives containing the uncharged urea-equivalent groups. This behaviour indicates, in this class of compounds, the importance of H-bonding interactions with the receptor. When in the ring-open models the ethanediamino substructure is substituted for the piperazine ring additional decrease in activity occurs. Hemmung der α1-Adrenozeptoraktivitat durch ringoffene Analoge des Prazosins Die Synthese und die Strukturanalyse von Analogen des Prazosins, die einen geoffneten Ring haben, werden beschrieben. Diese Analogen haben eine Guanidin-Struktur oder eine gleichwertige Harnstoffgruppe. Die Offnung des Pyrimidinringes des Prazosins ist sehr wichtig fur die Affinitat zum α1-Adrenorezeptor. Die pA2 Werte dieser Folgeprodukte sind 104–105 niedriger als die von Prazosin. Die Abnahme der Affinitat beruht wahrscheinlich auf einer negativen konformativen Einwirkung auf die α1-Rezeptoren. Das Derivat 5 enthalt eine Guanidingruppe, die bei physiologischem pH geladen ist. 5 hat dieselbe Aktivitat wie die anderen 1-Derivate, die eine gleichwertige Harnstoffgruppe beinhalten und nicht geladen sind. Das zeigt die Wichtigkeit von Wasserstoffbindungen mit dem Rezeptor. Wenn in dieser Verbindungsklasse der Piperazinering durch die Ethanediaminostruktur ausgewechselt wird, beobachtet man eine zusatzliche Abnahme der Aktivitat.

A new series of (((R-oxy)carbonyl)oxy)methyl esters of aspirin (ASA), bearing nitric oxide (NO) or hydrogen sulfide (H(2)S) releasing groups, was synthesized, and the compounds were evaluated as new ASA co-drugs. All the products were quite stable in buffered solution at pH 1 and 7.4. Conversely, they were all rapidly metabolized, producing ASA and the NO/H(2)S releasing moiety used for their preparation. Consequent on ASA release, the compounds were capable of inhibiting collagen-induced platelet aggregation of human platelet-rich plasma (PRP). The simple NO/H(2)S donor substructures were able to relax contracted rat aorta strips, with a NO- and H(2)S-dependent mechanism, respectively, but they either did not trigger antiaggregatory activity or displayed antiplatelet potency markedly below that of the related co-drug. The new products might provide a safer and improved alternative to the use of ASA principally in its anti-inflammatory and antithrombotic applications.

The synthesis and structure of a trimer 5 of the furoxan system are reported. The probable origin of this derivative is the dimerization of the intermediate 4-phenyl-3-furoxancarbonitrile oxide (4) obtained by decomposition of the corresponding nitrolic acid 3. The title compound shows a high level of activity as vasodilator and inhibitor of platelet aggregation.

A series of analogues of prazosin, in which 1-methyl or 1-phenylpyrazole moieties were substituted for the furan ring, were synthesized and studied for their alpha 1-adrenoceptor antagonist activity. The role of the five member heterocyclic substructures in determining the affinity for the alpha 1-receptor is briefly discussed.

Nitrooxymethyl-substituted derivatives of Rofecoxib were synthesized and tested for their cyclooxygenase (COX)-inhibiting activity in whole human blood, vasodilator potency on rat aorta strips, and for their capacity of inhibiting platelet aggregation of human platelet-rich plasma. The results show that their potency and selectivity in inhibiting COX isoforms, as well as their anti-aggregatory properties, are closely dependent on the position at which the NO-donor nitrooxymethyl function is introduced into the Rofecoxib scaffold. All the products were capable of dilating rat aorta strips precontracted with phenylephrine in a dose-dependent manner, through a cGMP-dependent mechanism. Compound 10 emerged as a quite potent COX-2-selective inhibitor endowed with good vasodilator activity. Interestingly, compound 19 behaved as a potent selective COX-1 inhibitor, and displayed good vasodilator and anti-aggregatory properties. The hydroxymethyl derivatives, potential metabolites of the nitrooxymethyl analogues, were similarly studied for a comparison.

Recently a new series of nitrooxy-acyl derivatives of salicylic acid (SA) was described presenting similar anti-inflammatory activities but reduced or no gastrotoxicity compared to aspirin. In this work, lipophilicity and permeability profiles of SA derivatives were performed to evaluate their ADME properties related to oral or transdermic delivery. All tested compounds showed potential good passive permeation through gastrointestinal track and also through percutaneous barrier which could be a way to avoid the first hepatic pass.

Nitric oxide (NO) donor antioxidants are a class of polyvalent drugs which is the focus of great interest today. They are potentially useful for the treatment of many forms of cardiovascular diseases, including the myocardial ischemia/reperfusion (I/R) damage which seems to be due to both a burst of reactive oxygen species (ROS) and a reduced release of NO during reperfusion. In this paper the results of a study on the ability of new NO-donor antioxidants containing the phenol vitamin E substructure and furoxan moiety to attenuate I/R damage are reported. The compounds under study are obtained by combining the phenol moiety (6-hydroxy-2,2,5,7,8-pentamethylchroman) present in vitamin E with differently substituted furoxan substructures endowed with different capacity of NO-release. Their antioxidant and NO-dependent vasodilator activities are reported. The I/R experiments were performed on isolated rat heart preparations perfused at a constant flow. After 20 min of stabilization, global ischemia was obtained by interrupting the perfusion for 30 min. After ischemia the hearts were reperfused for 2 h. The compounds were added to the perfusion buffer during the first 20 min of reperfusion. At the end of each experiment, the infarct size was measured with nitro-blue tetrazolium. From the results it appears that the limitation of the infarct area is favoured by an appropriate balance between NO-donor and antioxidant properties and that these two actions are synergic.

Synthesis and structural characterization of the 4-phenylbutane-1,2-diyl dinitrate and of the erythro and threo diastereoisomers of 4-phenylbutane-1,2,3-triyl trinitrate as well as the HPLC chiral separation of the corresponding racemic mixtures are reported. Vasodilator activity of the single enantiomers of these products, of 4-phenylbutyl nitrate, and of the previously described phenylpropyl analogues were assessed on rat aorta strips precontracted with phenylephrine. The compounds were able to relax the contracted tissue in a concentration dependent manner. In the couples of antipodes, a complete lack of enantioselectivity was observed as far as the vasodilator potency is concerned. The concentration response curves of the products, with the exception of those of all the trinitrooxy substituted models, were rightward shifted in the presence of ALDH-2 inhibitors. Mono and dinitrates, but not trinitrates, displayed in vitro cross-tolerance with GTN. This new series of nitric acid esters is an interesting tool that can help to shed light on the unresolved puzzle of nitrate pharmacology. Selected members are worthy of additional study as potential drugs.

Nitrooxymethyl-substituted analogues of celecoxib were synthesized and tested for their cyclooxygenase (COX)-inhibiting, vasodilator, and anti-aggregatory activities, as well as for their metabolic stability in human serum and whole blood. The results showed their potency and selectivity in inhibiting the COX isoforms, evaluated in whole human blood, as well as their anti-aggregatory activity to depend closely on the position at which the NO-donor moiety is introduced. All products dilated rat aorta strips precontracted with phenylephrine in a dose-dependent manner through a cGMP-dependent mechanism. They were stable in human serum while, in blood, they were metabolically transformed, principally to the related alcohols.

The article addresses the design of multitarget drugs, namely, compounds capable of interacting with more than one target simultaneously. These agents could be useful tools in the therapy of complex diseases such as cardiovascular and inflammatory diseases. An interesting case of multitarget compounds are nitric oxide (NO)-donor hybrids, structures which combine the physiological properties of NO with those of a lead drug. In particular, the authors discuss the symbiotic approach used to design NO-donor nonsteroidal anti-inflammatory drugs (NO-NSAIDs) and NO-donor antioxidants. The former could be useful agents in the treatment of anti-inflammatory diseases being devoid of gastro- and cardiotoxicity, the latter could be a valid approach to the treatment of many cardiovascular diseases.

In official doping controls, about 300 drugs and metabolites have to be screened for each sample. Moreover, the number of determinations to be routinely processed increases continuously as the number of both samples and potential illicit drugs keeps growing. As a consequence, increasingly specific, sensitive, and, above all, fast methods for doping controls are needed. The present study presents an efficient fast-GC/MS approach to the routine screening of two different classes of doping agents, namely beta-adrenoceptor ligands and diuretics (belonging to the S3, P2, and S5 groups of the WADA list of prohibited substances). Narrow bore columns (100 mm id) of different lengths and coated with apolar stationary phases were successfully used to separate the derivatized analytes; preliminary experiments (results not shown) showed better performances with OV-1701 for the separation of beta-adrenoceptor ligands. On the same stationary phase some diuretics required too high a temperature or a long isothermal time for elution, in which case a DB1-MS column was preferred. Two methods of sample preparation, derivatization, and analysis were used on aqueous standard mixtures of, respectively, (i) eight beta-adrenoceptor ligands, including five beta-antagonists (acebutolol, alprenolol, atenolol, metoprolol, pindolol) and three beta2-agonists (salbutamol, clenbuterol, terbutaline) and (ii) seventeen diuretic drugs (acetazolamide, althiazide, bendroflumethiazide, bumethanide, canrenone, chlorothiazide, chlortalidone, clopamide, ethacrinic acid, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, indomethacine, spironolactone, triamterene, trichloromethiazide) and one masking agent (probenecid). The mixture of beta-adrenoceptor ligand derivatives was efficiently separated in about 5.6 min, while the one of 18 diuretics and masking agents required less than 5 min for analysis. Limits of detection were from 1 microg/L for pindolol, ethacrinic acid, furosemide, indomethacine, and trichloromethiazide, to 20 microg/L for terbutaline, salbutamol, and metoprolol, and 50 microg/L for clopamide; the instrumental repeatability proved to be excellent (area RSD%

As an introductory study of in vitro vasodilating activity, the access to the four stereomers of 1-phenylglyceryl trinitrate is described using achiral and chiral chromatography. For semi-preparative separation of the enantiomers, a Chiralcel OD (250 x 10 mm, 10 microm) was used. Catalytic reduction leading to the corresponding stereomers of 1-phenylglycerol allowed absolute configuration assignments. The same methods were used for the separation and configuration assignment of the enantiomers of 3-phenylpropane-1,2-diyl dinitrate.

Recently a series of H3-antagonists related to Imoproxifan was realised (I); in these products the oxime substructure of the lead was constrained in NO-donor furoxan systems and in the corresponding furazan derivatives. In this paper, a new series of compounds derived from I by substituting the imidazole ring with the ethoxycarbonylpiperazino moiety present in the non-imidazole H3-ligand A-923 is described. For all the products synthesis and preliminary pharmacological characterisation, as well as their hydrophilic–lipophilic balance, are reported. The imidazole ring replacement generally results in a decreased H3-antagonist activity with respect to the analogues of series I and, in some cases, induces relaxing effects on the electrically contracted guinea-pig ileum, probably due to increased affinity for other receptor systems.

Synthesis and pharmacological characterisation of a series of compounds in which the oxime substructure present in imoproxifan was constrained in the pentatomic NO-donor furoxan ring, as well as their structurally related furazan analogues devoid of NO-donating properties, are described. The whole series of products displayed reversible histamine H 3 -antagonistic activity on guinea-pig ileum. 4-(4-(3-(1 H -Imidazol-4-yl)propoxy)phenyl)furoxan-3-carbonitrile 16 was also able to induce partial relaxation when added to the bath after electrical contraction of the guinea-pig ileum during the study of its H 3 -antagonistic properties. This phenomenon seems to be dependent on NO-mediated sGC activation. The lipophilic–hydrophilic balance of all the products was investigated.

Synthesis and pharmacological characterisation of a series of compounds obtained by joining, through appropriate spacers, NO-donor furoxan and nitrooxy moieties to the imidazole ring, as well as their structurally related analogues devoid of NO-donating properties are described. All the products were studied for their capacity to interact with H3-receptors present on the guinea-pig ileum and with H2-receptors present on guinea-pig right atrium. The whole series of products displayed reversible H3-antagonistic activity. No activity on H2-receptors was observed when the products were tested at 10 μM concentration. Many of the products were also able to induce partial relaxation when added to the bath after electrical contraction of the guinea-pig ileum during the study of their H3-antagonism. This phenomenon seems to be dependent on various factors; for some compounds it proved to be dependent on NO-mediated sGC activation, for other products it could be due to their weak M3-antagonism. The investigation of the lipophilic-hydrophilic balance of all the products indicates, for many of them, an ideal value to cross the blood-brain barrier.

A new series of calcium channel agonists structurally related to Bay K8644, containing NO donor furoxans and the related furazans unable to release NO, is described. The racemic mixtures were studied for their action on L-type Ca 2+ channels expressed in cultured rat insulinoma RINm5F cells. All the products proved to be potent calcium channel agonists. All the racemic mixtures, with the only exception of the carbamoyl derivatives 9, 12 endowed with scanty solubility, were separated by chiral chromatography into the corresponding enantiomers; the (+) enantiomers were found to be potent agonists while the (-) ones were feeble antagonists. The racemic mixtures were also assessed for their positive inotropic activity on electrically stimulated rat papillary muscle and for their ability to increase Ca 2+ entry into the vascular smooth muscle of rat aorta strips. The cyanofuroxan 8 proved to be an interesting product with dual Ca 2+ -dependent positive inotropic and NO-dependent vasodilating activity.

A new class of NO-donor phenol derivatives is described. The products were obtained by joining appropriate phenols with either nitrooxy or 3-phenylsulfonylfuroxan-4-yloxy moieties. All the compounds proved to inhibit the ferrous salt/ascorbate induced lipidic peroxidation of membrane lipids of rat hepatocytes. They were also capable of dilating rat aorta strips precontracted with phenylephrine.

The article focuses attention on furoxan derivatives (1,2,5 oxadiazole 2-oxides) as NO donors. Possible mechanisms for NO release from these products in physiological solution and in segments of rabbit femoral artery are briefly considered. The in vitro anti aggregatory activities and the in vitro and in vivo vasodilating properties of a number of furoxans are examined with particular reference to involvement of NO in these actions. The use of the furoxan system to design new NO donor/drug hybrids is discussed in connection with the problem of the balance between NO- and drug dependent activities of the resulting structures. Whether other biological activities (as yet, little studied) of furoxans, such as their antiparasite, antimicrobial, and antitumoral effects, are NO dependent, is a matter still to be explored.

Synthesis and pharmacological characterisation of a series of products obtained by coupling the H(3)-antagonist SKF 91486 through appropriate spacers with the NO-donor 3-phenylfuroxan-4-yloxy and 3-benzenesulfonylfuroxan-4-yloxy moieties, as well as with the corresponding furazan substructures, devoid of NO-donating properties, are reported. All the products were tested for their H(3)-antagonistic and H(2)-agonistic properties on electrically-stimulated guinea-pig ileum segments and guinea-pig papillary muscle, respectively. The whole series of compounds displayed good H(3)-antagonist behaviour and feeble partial H(2)-agonist activity. Among furoxan derivatives, the benzenesulfonyl hybrid 28, a good NO-donor, triggered a dual NO-dependent muscle relaxation and H(3)-antagonistic effect on guinea-pig intestine.

A series of nitroso compounds gem -substituted with electron-withdrawing groups (R(2)C(X)NO, R=alkyl, X=NO(2), CN, Cl), were studied for their in vitro and in vivo vasodilating properties as well as for their ability to activate soluble guanylate cyclase (sGC) in RFL-6 cells. All the compounds, with the sole exception of chloro derivative, display good in vitro vasodilating action and are able to increase the basal level of cGMP. Their potencies as vasodilators decrease in the presence of oxyhaemoglobin, a scavenger of nitric oxide (NO). The haemodynamic profile of the most interesting compounds, assessed in anaesthetized pigs, is also in line with a release of NO from these compounds.

A series of analogues of prazosin, in which 1-methyl or 1-phenylpyrazole moieties were substituted for the furan ring, were synthesized and studied for their alpha 1-adrenoceptor antagonist activity. The role of the five member heterocyclic substructures in determining the affinity for the alpha 1-receptor is briefly discussed.

A number of ranitidine analogues in which the diamino-1,2,5-thiadiazole 1-oxide substructure bearing alkyl chains of different length is present as the urea equivalent group, were synthesised and studied for their lipophilic and H2 antagonist properties. Derivatives which displayed a logP≤3 behaved as competitive antagonists of histamine at H2 receptors present on guinea pig right atrium. The remaining more lipophilic members of the series showed an insurmountable antagonism not completely reversible after prolonged washing. A binding study suggested that an increase in the length of alkyl chain gave rise to hydrophobic interactions with the receptor which were responsible for the apparent irreversible H2 antagonism shown by the higher homologues of the series.

The synthesis, characterization, NO donor properties, and in vitro vasodilating activity of a series of water soluble furoxans (5-14a,b) are described. All of the compounds released NO when treated with a large excess of cysteine under physiological conditions (pH 7.4; 37 degrees C). The amount of NO produced after 1 h of incubation was evaluated by detecting nitrites, via the Griess reaction. Derivatives 5b, 7b, and 14b were able to release nitric oxide also in the absence of the thiol cofactor. The initial rates of NO release were determined at different concentrations, using a spectrophotometric technique based on the NO-induced oxidation of oxyhemoglobin (HbO2) to methemoglobin (MetHb). The initial rates of NO release were linearly dependent on the concentrations of the single compounds. The vasodilating potency (EC50) of all the derivatives was assessed on rat aortic strips precontracted with noradrenaline. Correlation between potency and initial NO release rate is discussed.

The syntheses of almost all N-heterocycles have now been successfully performed under microwave irradiation and have provided significant improvements in the reaction time and efficiency. The peculiar properties of dielectric heating give it the ability to strongly promote cyclocondensation, cycloaddition and selective N-heterocycle functionalisation and it has, therefore, very much caught the attention of the medicinal chemistry community. In this work, we present an overview of recent literature and technical advances in this research field with the aim of providing insight into the applications of microwave-assisted synthesis in the preparation of the main drug categories that contain N-heterocycle scaffolds.

Models of amphiphilic NO-donor antioxidants 24-26 were designed and synthesized. The products were obtained by linking a lipophilic tail (C(6), C(8), C(10)) with a polar head constituted by the 2,6-dimethoxyphenol antioxidant joined to the NO-donor 3-furoxancarboxamide substructure through a bridge containing a quaternary ammonium group. Compound 23, containing the shortest C(2)-alkyl chain, was also studied as a reference. The antioxidant properties (TBARS and LDL oxidation assays) and the vasodilator properties of the compounds were studied in vitro. The ability of these products to interact with phospholipid vesicles was also investigated by NMR techniques. The results indicate that both activities are modulated by the ability of the compounds to accumulate on phospholipid layers.

Several NO donor 3,4-diphenylfuroxan (= 3,4-diphenyl-1,2,5-oxadiazole 2-oxide) derivatives were synthesized and tested for their COX-inhibiting activities. The products were found to be selective COX-2 inhibitors, similar to the structurally related furazans (3,4-diphenyl-1,2,5-oxadiazole), devoid of the NO release property. This behavior was confirmed by a molecular-docking study. The NO-dependent platelet anti-aggregatory and vasodilating activities of the new furoxans 5-7 were studied in vitro. These properties can be modulated by inserting an appropriate spacer between the 4-phenyl group and the furoxan ring, giving rise to new, selective COX-2 furoxan derivatives endowed with anti-aggregatory and vasodilating activities, and with potentially reduced cardiotoxicities.