New N- and O-arylpiperazinylalkyl pyrimidines and 2-methylquinazolines derivatives as 5-HT7 and 5-HT1A receptor ligands: Synthesis, structure-activity relationships, and molecular modeling studies.

Based on our earlier studies of structure activity relationships on 4-substituted piperazine derivatives, in this work we synthesized a novel set of long-chain arylpiperazines with the purpose of elucidating if some structural modifications in the terminal fragment could affect the binding affinity for the 5-HT7 and 5-HT1A receptors. In this new series, the quinazolinone system of the previous derivatives was replaced by a 6-phenylpyrimidine or a 2-methylquinazoline, which were used as versatile building blocks for the preparation of new compounds. A 4-arylpiperazine moiety through a five methylene chain was anchored at the nitrogen or oxygen atom of the heterocyclic scaffolds. The substituents borne by the piperazine nucleus were phenyl, phenylmethyl, 3- or 4-chlorophenyl, and 2-ethoxyphenyl. Binding tests, performed on human cloned 5-HT7 and 5-HT1A receptors, showed that, among the newly synthesized derivatives, 4-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentoxy]-6-phenyl-pyrimidine (13) and 3-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentyl]-2-methyl-4(3H)-quinazolinone (20) displayed the best affinity values, Ki=23.5 and 8.42nM for 5-HT7 and 6.96 and 2.99nM for 5-HT1A receptors, respectively. Moreover, the functional properties for both compounds were further evaluated using the cAMP assay. Finally, a molecular modeling study has been performed for 5-HT7 and 5-HT1A receptor homology models to investigate the binding mode of N- and O-alkylated pyrimidinones/pyrimidines 4-13, 2-methylquinazolinones/quinazolines 17-22, and previously reported 2- and 3-substituted quinazolinones 23-30.

Design and synthesis of new homo and hetero bis-piperazinyl-1-propanone derivatives as 5-HT7R selective ligands over 5-HT1AR.

In this work we report the discovery of new homo and hetero bis-piperazinyl-1-propanone derivatives as selective ligands for 5-HT7 over 5-HT1A receptor. These newly synthesized compounds possess a 4-arylpiperazine linked through an acyl spacer to another substituted piperazine system and were tested for their binding properties on human cloned 5-HT1A and 5-HT7 serotonin receptors. Among these, phenyl, 4- and 2-chlorophenyl, 2-methoxyphenyl, 2-pyridyl, and 2-pyrimidyl derivatives 15, 24, 25, and 27-29 displayed nanomolar affinity values for the 5-HT7 receptor (Ki 23.5-52.0nM) and no affinity for the 5-HT1A receptor.

Analysis of mechanisms for memory enhancement using novel and potent 5-HT1A receptor ligands.

In light of the involvement of serotonergic 5-HT1A receptors in the mediation of the memory of aversive events, the potent and selective 5-HT1A receptor antagonists, MC18 fumarate and VP08/34 fumarate, were tested in the passive avoidance task (PA), a rodent model of instrumental conditioning. Either alone or in combination with the prototypical agonist 8-OH-DPAT, MC18 fumarate at doses (0.1, 0.3 and 1mg/kg given 15min prior to training) exerted a dose-dependent facilitation of PA memory retention. When administered 15min prior to 8-OH-DPAT (0.3 and 1mg/kg), MC18 fumarate at a dose of 0.3mg/kg, enhanced significantly the impairment of PA retention caused by 8-OH-DPAT (1mg/kg). However, VP08/34 fumarate given at the same doses exerted no statistically effect on PA retention memory. Furthermore, VP08/34 fumarate given 15min prior to 8-OH-DPAT (0.3 and 1mg/kg) only slightly enhanced the PA impairment induced by 8-OH-DPAT. In conclusion, the profile of MC18 fumarate is intriguing since it behaves in a manner which differs from both full receptor antagonists such as NAD-299 or partial receptor agonists. The results also illustrate the importance of subtle receptor interaction and probably ligand efficacy in determining the actions of two almost identical 5-HT1A receptor ligands in cognitive function such as instrumental learning.

Novel imidazole derivatives as heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2) inhibitors and their cytotoxic activity in human-derived cancer cell lines.

Heme oxygenase (HO) is a cytoprotective enzyme that can be overexpressed in some pathological conditions, including certain cancers. In this work, novel imidazole derivatives were designed and synthesized as inhibitors of heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2). In these compounds the imidazole ring, crucial for the activity, is connected to a hydrophobic group, represented by aryloxy, benzothiazole, or benzoxazole moieties, by means of alkyl or thioalkyl chains of different length. Many of the tested compounds were potent and/or selective against one of the two isoforms of HO. Furthermore, most of the pentyl derivatives showed to be better inhibitors of HO-2 with respect to HO-1, revealing a critical role of the alkyl chain in discriminating between the two isoenzymes. Compounds which showed the better profile of HO inhibition were selected and tested to evaluate their cytotoxic properties in prostate and breast cancer cell lines (DU-145, PC3, LnCap, MDA-MB-231, and MCF-7). In these assays, aryloxyalkyl derivatives resulted more cytotoxic than benzothiazolethioalkyl ones; in particular compound 31 was active against all the cell lines tested, confirming the anti-proliferative properties of HO inhibitors and their potential use in the treatment of specific cancers.

Synthesis and binding properties of new long-chain 4-substituted piperazine derivatives as 5-HT1A and 5-HT7 receptor ligands.

New long-chain 4-substituted piperazines linked to a thienopyrimidine or a quinazoline system were synthesized and tested for their binding properties on human cloned 5-HT1A and 5-HT7 serotonin receptors. Some structural modifications, concerning tree main portions, that is, terminal fragment, chain length, and aryl substituents, were examined. The 2- and 3-substituted thienopyrimidinone and quinazolinone systems were selected as terminal fragment and a chain length of four or five methylene units was set. Explored aryl substituents were phenyl, phenylmethyl, 3- or 4-chlorophenyl, and 2-ethoxyphenyl. Title compounds showed affinity for 5-HT1A and 5-HT7 receptors. In particular, 2-ethoxyphenyl derivatives 40 and 45 displayed Ki values in the nanomolar range on both receptors, acting as dual ligands.

Synthesis and endothelin receptors binding affinity of new 1,3,5- substituted pyrrole-2-carboxylic acid derivatives.

The interest of researchers for ligands of the endothelin receptors ETA and ETB is due to their extensive therapeutic potential. In particular, receptor antagonists are useful in a number of diseases such as pulmonary hypertension, acute myocardial infarction, congestive heart failure, renal failure, and atherosclerosis. In the context of our research program aimed to the development of new endothelin receptor ligands, in this paper we describe the synthesis and structure- activity relationships of a new series of 1,3,5-substituted pyrrole-2-carboxylic acid derivatives 27-40 possessing the structural features for ET receptors binding. New synthesized compounds were tested on ETA and ETB receptors stably expressed in CHO cells and some of them showed interesting affinity and selectivity towards ETA receptors.

Structure-activity relationships and molecular modeling studies of novel arylpiperazinylalkyl 2-benzoxazolones and 2-benzothiazolones as 5-HT(7) and 5-HT(1A) receptor ligands.

A novel series of arylpiperazinylalkyl 2-benzoxazolones and 2-benzothiazolones 18-38 was designed, synthesized and tested to evaluate their affinity for the 5-HT7 and 5-HT1A receptors. Compounds with a 2-benzothiazolone nucleus generally had affinity values higher than the corresponding 2-benzoxazolone compounds. In particular, derivatives possessing a six or seven carbon chain linker between 2-benzothiazolone and arylpiperazine had Ki values in the subnanomolar range for the 5-HT1A receptor and in the low nanomolar range for the 5-HT7 receptor, indicating that they may be interesting dual ligands. Molecular modeling studies revealed different docking poses for the investigated compounds in homology models of 5-HT1A and 5-HT7 receptors, which explained their experimentally determined affinities and general low selectivity. Additionally, structural interaction fingerprints analysis identified the important amino acid residues for the specific interactions of long-chain arylpiperazines within the binding pockets of both serotonin receptors.

High affinity ligands and potent antagonists for the α1D-adrenergic receptor. Novel 3,8-disubstituted [1]benzothieno[3,2-d]pyrimidine derivatives.

A new series of high affinity ligands and antagonists for the α1D-adrenergic receptor (AR) has been discovered. New molecules present a [1]benzothieno[3,2-d]pyrimidin-2,4(1H,3H)-dione or a [1]benzothieno[3,2-d]pyrimidin-4(3H)-one scaffold and bear a 2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl moiety in the 3-position and various amide substituents in the 8-position. In binding assays at the three human cloned α1A-, α1B-, and α1D-AR subtypes, they showed high affinity values, particularly for the α1D-AR subtype. Compound 22 (RX18), N(1)-methyl-N(5)-[3-[2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl]-2,4-dioxo-1,2,3,4-tetrahydro[1]benzothieno[3,2-d]pyrimidin-8-yl]-N(1)-(phenylmethyl)pentanediamide, was the most interesting in the series displaying very high affinity (pKi = 10.25) and potent antagonism (pKb = 9.15) when tested in a functional assay at the α1D-AR.

Antioxidant activity and phenolic content of microwave-assisted Solanum melongena extracts.

Eggplant fruit is a very rich source of polyphenol compounds endowed with antioxidant properties. The aim of this study was to extract polyphenols from eggplant entire fruit, pulp, or skin, both fresh and dry, and compare results between conventional extraction and microwave-assisted extraction (MAE). The effects of time exposure (15, 30, 60, and 90 min) and solvent (water 100% or ethanol/water 50%) were also evaluated. The highest amount of polyphenols was found in the extract obtained from dry peeled skin treated with 50% aqueous ethanol, irradiated with microwave; this extract contained also high quantity of flavonoids and showed good antioxidant activity expressed by its capacity to scavenge superoxide anion and to inhibit lipid peroxidation.

Evaluation of novel aryloxyalkyl derivatives of imidazole and 1,2,4-triazole as heme oxygenase-1 (HO-1) inhibitors and their antitumor properties.

A novel series of aryloxyalkyl derivatives of imidazole and 1,2,4-triazole, 17-31, was designed and synthesized as inhibitors of heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2). Some of these compounds were found to be good inhibitors of HO-1, in particular those carrying an imidazole moiety as azolyl group and a 3-bromo or 4-iodophenyl as aryl moiety. The most potent compounds 6 and 30 were selected and studied for their antitumor properties in a model of LAMA-84 R cell line overexpressing HO-1 and resistant to imatinib mesylate (IM), a tyrosine-kinase inhibitor used in the treatment of multiple types of cancer, most notably Philadelphia Chromosome positive (Ph(+)) Chronic Myelogenous Leukemia (CML). Results show that both 6 and 30 sensitized LAMA-84 R cell line to antitumor properties of IM.

Antitumor properties of substituted (αE)-α-(1H-indol-3-ylmethylene)benzeneacetic acids or amides.

A novel class of indole derivatives characterized by a (αE)-α-(1H-indol-3-ylmethylene)benzeneacetic acid or amide scaffold was synthesized. These derivatives, assayed for cell-growth inhibition activity against a panel of six different tumor cell lines, showed strong antiproliferative activity and selectivity mainly towards DU145 cell line. In particular, compounds 2d-m and 5 stand out for their cell growth inhibitory activity and, among them, compound 2d emerged for its selectivity towards DU145 with respect to other tested tumor cell lines. DU145 treated with 1µM of 2d for 72h showed p21(Cip1) induction and suppression of Akt signaling together with induction of Rb. From a computational point of view, two different approaches were used in order to study topology and electronic properties of the novel compounds and to shed light on their drug-likeness properties. Firstly, topological and electronic features of the compounds endowed with the most relevant biological activity were deepened; in parallel, some ADME properties like solubility and permeability were predicted.

Novel inhibitors of nitric oxide synthase with antioxidant properties.

We previously described a series of imidazole-based inhibitors substituted at N-1 with an arylethanone chain as interesting inhibitors of neuronal nitric oxide synthase (nNOS), endowed with good selectivity vs endothelial nitric oxide synthase (eNOS). As a follow up of these studies, several analogs characterized by the presence of substituted imidazoles or other mono or bicyclic nitrogen-containing heterocycles instead of simple imidazole were synthesized, and their biological evaluation as in vitro inhibitors of both nNOS and eNOS is described herein. Most of these compounds showed improved nNOS and eNOS inhibitory activity with respect to reference inhibitors. Selected compounds were also tested to analyze their antioxidant properties. Some of them displayed good capacity to scavenge free radicals and ability to reduce lipid peroxidation.

Synthesis and molecular modeling of 1H-pyrrolopyrimidine-2,4-dione derivatives as ligands for the α1-adrenoceptors.

Three different series of 1H-pyrrolopyrimidine-2,4-dione derivatives were designed and synthesized as ligands for the α(1)-adrenergic receptors (α(1)-ARs). A microwave-assisted protocol was developed in order to improve purity and yields of some final products. The majority of the synthesized compounds, tested in binding assays, displayed α(1)-AR affinities in the nanomolar range. Highest affinity values were found in derivatives 10b and 10c (K(i)=1.4 nM for both) whereas compound 10e was endowed with the best profile in term of α(1)-AR affinity (K(i)=2.71 nM) coupled with high selectivity towards 5-HT(1A) receptors (K(i) >10,000). Molecular docking studies were performed on human α(1)-ARs and human 5-HT(1A) receptors in order to rationalize the observed experimental affinity and selectivity; these computational studies helped to clarify molecular requirements for the design of high-selective α(1)-adrenergic ligands.

Novel 4-phenylpiperidine-2,6-dione derivatives. Ligands for α1-adrenoceptor subtypes.

A number of new 4-phenylpiperidine-2,6-diones bearing at the 1-position an ω-[4-(substituted phenyl)piperazin-1-yl]alkyl moiety were designed and synthesized as ligands for the α(1)-adrenergic receptor (α(1)-AR) subtypes. Some synthesized compounds, tested in binding assays for the human cloned α(1A)-, α(1B)-, and α(1D)-AR subtypes, displayed affinities in the nanomolar range. Highest affinity values were found in derivatives having a butyl connecting chain between the 4-phenylpiperidine-2,6-dione and the phenylpiperazinyl moieties. 1-[4-[4-(2-Methoxyphenyl)piperazin-1-yl]butyl]-4-phenylpiperidine-2,6-dione (34) showed the best affinity for the α(1A)-AR (pK(i) = 8.74) and 10-fold selectivity compared to the other two α(1)-AR subtypes. Some representative compounds were also tested in order to evaluate their effects on the signal transduction pathway coupled to α(1)-AR subtypes. They all blocked norepinephrine-induced stimulation of inositol phospholipid hydrolysis, thus behaving as antagonists. Binding data were used to refine a previously developed pharmacophoric model for α(1D)-ARs. The revised model shows a highly predictive power and could be useful for the future design of high affinity α(1D)-AR ligands.

Synthesis of new arylpiperazinylalkylthiobenzimidazole, benzothiazole, or benzoxazole derivatives as potent and selective 5-HT1A serotonin receptor ligands.

A series of new compounds containing a benzimidazole, benzothiazole, or benzoxazole nucleus linked to an arylpiperazine by different thioalkyl chains was prepared. They were tested in radioligand binding experiments to evaluate their affinity for 5-HT 1A and 5-HT 2A serotonergic, alpha 1 adrenergic, D1, and D2 dopaminergic receptors. Many of tested compounds showed an interesting binding profile; in particular, 36 displayed very high 5-HT 1A receptor affinity and selectivity over all the other investigated receptors. Selected compounds, evaluated in functional assays, showed antagonistic or partial agonistic activity at 5-HT 1A receptor. An extensive conformational research using both NMR and modeling techniques indicated that extended conformations predominated in vacuum, in solution and during interactions with 5-HT 1A receptor. Finally, the elaborated binding mode of selected compounds at 5-HT 1A receptor was used to explain the influence of spacer length on ligands affinity.

Synthesis and receptor binding of new thieno[2,3-d]-pyrimidines as selective ligands of 5-HT(3) receptors.

With the aim to develop new potent and selective ligands of 5-HT(3)-type serotonin receptors and to acquire more information on their structure-affinity relationships, new thieno[2,3-d]pyrimidine derivatives 32-39 were synthesized and their binding to 5-HT(3) versus 5-HT(4 )receptors was studied. Some of these new compounds exhibit good affinity for cortical 5-HT(3) receptors, but not for 5-HT(4) receptors. Among these derivatives, 6-ethyl-4-(4-methyl-1-piperazinyl)-2-(methylthio)thieno[2,3-d]pyrimidine 32 is the most potent ligand (K(i) = 67 nM); it behaves as a competitive antagonist of the 5-HT(3) receptor function in the guinea pig colon. Its binding interactions with 5-HT(3A )receptors were analysed by using receptor modelling and comparative docking.