Stefano Guglielmo

Phenylsulfonylfuroxans as Modulators of Multidrug-Resistance-Associated Protein-1 and P-Glycoprotein

A series of furoxan derivatives were studied for their ability to interact with P-gp and MRP1 transporters in MDCK cells overexpressing these proteins. 3-Phenylsulfonyl substituted furoxans emerged as the most interesting compounds. All of them were capable of inhibiting P-gp, and a few also were capable of inhibiting MRP1. Substituents at the 4-position of 3-phenylsulfonylfuroxan scaffold were able to modulate the selectivity and the intensity of inhibition. In some cases, they reverted MRP1 inhibitor activity, namely, they were capable of potentiating MRP1 dependent efflux. When compounds 16 and 17 were coadministered with doxorubicin, they restored a high degree of the activity of the antibiotic. Preliminary immunoblotting studies carried out on these two compounds indicate that they are capable of nitrating P-gp, which in this form is likely unable to efflux the antibiotic.

Nitric oxide donor doxorubicins accumulate into Doxorubicin-resistant human colon cancer cells inducing cytotoxicity.

Products 4 and 5, obtained by conjugation of doxorubicin with nitric oxide (NO) donor nitrooxy and phenylsulfonyl furoxan moieties, respectively, accumulate in doxorubicin-resistant human colon cancer cells (HT29-dx), inducing high cytotoxicity. This behavior parallels the ability of the compounds to generate NO, detected as nitrite, in these cells. Preliminary immunoblotting studies suggest that the mechanism that underlies the cytotoxic effect could involve inhibition of cellular drug efflux due to nitration of tyrosine residues of the MRP3 protein pump.

Furoxan-, alkylnitrate-derivatives and related compounds as anti-trypanosomatid agents: Mechanism of action studies

A series of over a hundred furoxans, alkylnitrates and related compounds were studied as growth inhibitors of the two major kinetoplastids of Latin America, Trypanosoma cruziand Leishmania spp., in in vitro assays. The most active compounds showed 50% inhibitory doses of the same order of that of Nifurtimox and Miltefosine, reference drugs used to treat Chagas Disease and Leishmaniasis respectively. Among the studied compounds derivative 4, presenting excellent inhibitory activity against the tryposmastigote and amastigote forms of T. cruzi, has emerged as a lead compound. Mechanism of action seems to involve mitochondrial dehydrogenases as a distinct effect with respect to Nifurtimox. Excreted metabolites, studied by NMR, showed a significant decrease in succinate, confirming the observed effect on the mitochrondrial dehydrogenases.

New Nitric Oxide or Hydrogen Sulfide Releasing Aspirins

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.

Synthesis, Physicochemical Characterization, and Biological Activities of New Carnosine Derivatives Stable in Human Serum As Potential Neuroprotective Agents

The synthesis and the physicochemical and biological characterization of a series of carnosine amides bearing on the amido group alkyl substituents endowed with different lipophilicity are described. All synthesized products display carnosine-like properties differentiating from the lead for their high serum stability. They are able to complex Cu(2+) ions at physiological pH with the same stoichiometry as carnosine. The newly synthesized compounds display highly significant copper ion sequestering ability and are capable of protecting LDL from oxidation catalyzed by Cu(2+) ions, the most active compounds being the most hydrophilic ones. All the synthesized amides show quite potent carnosine-like HNE quenching activity; in particular, 7d, the member of the series selected for this kind of study, is able to cross the blood-brain barrier (BBB) and to protect primary mouse hippocampal neurons against HNE-induced death. These products can be considered metabolically stable analogues of carnosine and are worthy of additional investigation as potential neuroprotective agents.

New praziquantel derivatives containing NO-donor furoxans and related furazans as active agents against Schistosoma mansoni

A series of NO-donor praziquantel hybrid compounds was obtained by combining praziquantel (PZQ) and furoxan moieties in a single entity. NO-donor properties of the furoxan derivatives were evaluated by detecting nitrite after incubation of the products in 7.4 pH buffered solution in the presence of L-cysteine. Structurally-related furazans, devoid of NO release capacity, were also synthesized for control purposes. All products were studied for their ability to inhibit recombinant Schistosoma mansoni thioredoxin glutathione reductase (TGR). Mobility and death of adult Schistosoma mansoni worms cultured in the presence of the products were evaluated versus PZQ. Analysis of the results showed that some products were endowed with both PZQ and NO-dependent antiparasitic properties. Compounds 6, 7, 18, and 24 emerged as the most interesting balanced hybrids, worthy of additional study on PZQ-resistant parasites.

Searching for new NO-donor aspirin-like molecules: Furoxanylacyl derivatives of salicylic acid and related furazans.

A new group of derivatives of salicylic acid containing NO-donor furoxans, and the related des-NO-furazans, were synthesized and evaluated as new aspirin-like molecules. Their stability was assessed in acid (pH 1) and physiological solutions (pH 7.4), and in human serum. No compound exhibited COX-inhibitory activity against COX-1 and COX-2 isoforms, when tested up to 100μM, respectively, on isolated platelets and on monocytes. Phenylsulfonyl- and cyano-substituted furoxans inhibited platelet aggregation induced by collagen in human platelet-rich plasma, through a cGMP dependent mechanism. Furoxan derivatives displayed cGMP-dependent vasodilator activities, tested on rat aorta strips precontracted with phenylephrine. All products showed anti-inflammatory activity similar to that of ASA, tested on rats by the carrageenan-induced paw edema assay. Unlike ASA, all products showed markedly reduced gastrotoxicity in a rat lesion model.

A new series of amodiaquine analogues modified in the basic side chain with in vitro antileishmanial and antiplasmodial activity.

The synthesis and the study of new amodiaquine derivatives bearing modified lateral basic chains as new agents with both antimalarial and antileishmanial activities are reported. The compounds were tested in vitro against Leishmania donovani MHOM/ET/67/HU3 and 2 strains of Plasmodium falciparum, 3D7 and K1. All the compounds show complex ionisation profiles. At physiological pH the ionised form(s) are in equilibrium with the uncharged form, while at acid pH all the products exist largely as protonated forms. The antiprotozoal profile indicates that all derivatives are endowed with both antimalarial and antileishmanial activity. Interestingly amodiaquine, together with some synthesised derivatives (11, 12, 15, 27, 34), displayed antileishmanial activity in the low micromolar range, although these compounds were also cytotoxic and have a narrow therapeutic window, most of the synthesised compounds proved to be potent antimalarials, a few of them showing a good activity against the chloroquine resistant K1 strain.

Amodiaquine analogues containing NO-donor substructures: Synthesis and their preliminary evaluation as potential tools in the treatment of cerebral malaria

The synthesis and physico-chemical properties of novel compounds obtained by conjugation of amodiaquine with moieties containing either furoxan or nitrooxy NO-donor substructures are described. The synthesised compounds were tested in vitro against both the chloroquine sensitive, D10 and the chloroquine resistant, W-2 strains of Plasmodium falciparum (P. falciparum). Most of the compounds showed an antiplasmodial activity comparable to that of the parent drug. By comparing the activities of simple related structures devoid of the ability to release NO, it appears that the contribution of NO to the antiplasmodial action in vitro is marginal. All the compounds were able to relax rat aorta strips with a NO-dependent mechanism, thus showing their capacity to release NO in the vessels. A preliminary in vivo study using Plasmodium berghei ANKA-infected mice showed a trend for prolonged survival of mice with cerebral malaria treated with compound 40, which is potent and fast amodiaquine-derived NO-donor, when compared with amodiaquine alone or with compound 31, a milder NO-donor. The two compounds showed in vivo antiplasmodial activity similar to that of amodiaquine.

Leishmanicidal Activities of Novel Synthetic Furoxan and Benzofuroxan Derivatives

ABSTRACT A novel series of furoxan (1,2,5-oxadiazole 2-oxide) (compounds 3, 4a and -b, 13a and -b, and 14a to -f) and benzofuroxan (benzo[c][1,2,5]oxadiazole 1-oxide) (compounds 7 and 8a to -c) derivatives were synthesized, characterized, and evaluated for in vitro activity against promastigote and intracellular amastigote forms of Leishmania amazonensis. The furoxan derivatives exhibited the ability to generate nitric oxide at different levels (7.8% to 27.4%). The benzofuroxan derivative 8a was able to increase nitrite production in medium supernatant from murine macrophages infected with L. amazonensis at 0.75 mM after 48 h. Furoxan and benzofuroxan derivatives showed remarkable leishmanicidal activity against both promastigote and intracellular amastigote forms. Compounds 8a, 14a and -b, and 14d exerted selective leishmanicidal activities superior to those of amphotericin B and pentamidine. In vitro studies at pH 5.4 reveal that compound 8a is stable until 8 h and that compound 14a behaves as a prodrug, releasing the active aldehyde 13a. These compounds have emerged as promising novel drug candidates for the treatment of leishmaniasis.