Synthesis and biological activity of novel substituted benzanilides as potassium channel activators. V

Analgesic Activity of 5-Acetamido-2-Hydroxy Benzoic Acid Derivatives and an In-Vivo and In-Silico Analysis of Their Target Interactions

The design, synthesis, and evaluation of novel non-steroidal anti-inflammatory drugs (NSAIDs) with better activity and lower side effects are big challenges today. In this work, two 5-acetamido-2-hydroxy benzoic acid derivatives were proposed, increasing the alkyl position (methyl) in an acetamide moiety, and synthesized, and their structural elucidation was performed using 1H NMR and 13C NMR. The changes in methyl in larger groups such as phenyl and benzyl aim to increase their selectivity over cyclooxygenase 2 (COX-2). These 5-acetamido-2-hydroxy benzoic acid derivatives were prepared using classic methods of acylation reactions with anhydride or acyl chloride. Pharmacokinetics and toxicological properties were predicted using computational tools, and their binding affinity (kcal/mol) with COX-2 receptors (Mus musculus and Homo sapiens) was analyzed using docking studies (PDB ID 4PH9, 5KIR, 1PXX and 5F1A). An in-silico study showed that 5-acetamido-2-hydroxy benzoic acid derivates have a better bioavailability and binding affinity with the COX-2 receptor, and in-vivo anti-nociceptive activity was investigated by means of a writhing test induced by acetic acid and a hot plate. PS3, at doses of 20 and 50 mg/kg, reduced painful activity by 74% and 75%, respectively, when compared to the control group (20 mg/kg). Regarding the anti-nociceptive activity, the benzyl showed reductions in painful activity when compared to acetaminophen and 5-acetamido-2-hydroxy benzoic acid. However, the proposed derivatives are potentially more active than 5-acetamido-2-hydroxy benzoic acid and they support the design of novel and safer derivative candidates. Consequently, more studies need to be conducted to evaluate the different pharmacological actions, the toxicity of possible metabolites that can be generated, and their potential use in inflammation and pain therapy.

Proximity Effects in Mass Spectra of Benzanilides

The analytical value of peaks arising by a proximity effect in the electron ionization mass spectra of benzanilides has been established by examining the spectra of numerous examples of general structure XC₆H₄NHCOC₆H₄Y. Significant [M-X]⁺ signals are observed only when X = Cl, Br, I or CH₃O in the 2-position. The presence of strong [M-X]⁺ signals, but negligibly weak [M-Y]⁺ peaks, even when the C-Y bond would be expected to break more readily than the C-X bond, indicates that these diagnostically useful signals do not arise by simple cleavage. Similarly, the presence of an appreciable [M-Cl]⁺ signal, but no [M-Br]⁺ signal, in the spectra of representative examples of 4-Br-2ClC₆H₃NHCOC₆H₄Y, reveals that loss of a substituent from the 2-position occurs much more rapidly than fission of a weaker bond to a substituent in the 4-position. These trends are interpreted in terms of cyclization of the ionized 2-substituted benzanilide, followed by elimination of the substituent originally in the 2-position, to form a protonated 2-arylbenzoxazole.

Mitochondrial K+ channels and their implications for disease mechanisms

The field of mitochondrial ion channels underwent a rapid development during the last decade, thanks to the molecular identification of some of the nuclear-encoded organelle channels and to advances in strategies allowing specific pharmacological targeting of these proteins. Thereby, genetic tools and specific drugs aided definition of the relevance of several mitochondrial channels both in physiological as well as pathological conditions. Unfortunately, in the case of mitochondrial K⁺ channels, efforts of genetic manipulation provided only limited results, due to their dual localization to mitochondria and to plasma membrane in most cases. Although the impact of mitochondrial K⁺ channels on human diseases is still far from being genuinely understood, pre-clinical data strongly argue for their substantial role in the context of several pathologies, including cardiovascular and neurodegenerative diseases as well as cancer. Importantly, these channels are druggable targets, and their in-depth investigation could thus pave the way to the development of innovative small molecules with huge therapeutic potential. In the present review we summarize the available experimental evidence that mechanistically link mitochondrial potassium channels to the above pathologies and underline the possibility of exploiting them for therapy.

Evaluation of Benzamide-chalcone Derivatives as EGFR/CDK2 inhibitor: Synthesis, in-vitro Inhibition, and Molecular Modeling Studies

BACKGROUND

EGFR (Epidermal Growth Factor Receptor) and CDK2 (Cyclin Dependent Kinase 2) are important targets in the treatment of many solid tumors and different ligands of these receptors share many common structural features.

OBJECTIVE

The study involved synthesis of benzamide-substituted chalcones and determination of their antiproliferative activity as well as preliminary evaluation of EGFR and CDK2 inhibitory potential using both receptor binding and computational methods.

METHODS

We synthesized 13 benzamide-substituted chalcone derivatives and tested their antiproliferative activity against MCF-7, HT-29 and U373MG cell-lines using Sulforhodamine B Assay. Four compounds were examined for activity against EGFR and CDK2 kinase. The compounds were docked into both EGFR and CDK2 using Glide software. The stability of the interactions for most active compound was evaluated by Molecular Dynamics Simulation using Desmond software. Molecular Docking studies on mutant EGFR (T790M, T790M/L858R, and T790M/C797S) were also carried out.

RESULTS

From the SRB assay, we concluded that compounds 1g, and 1k were effective in inhibiting the growth of MCF-7 cell line whereas the other compounds were moderately active. Most compounds were either moderately active or inactive on U373 MG and HT-29 cell line. Compounds 1g and 1k showed good inhibitory activity against CDK2 kinase while 1d and 1f were moderately active. Compounds 1d, 1f, 1g, and 1k were moderately active against EGFR kinase. Molecular docking reveals involvement of one hydrogen bond with Met793 in binding with EGFR however; it was not stable during simulation and these compounds bind to the receptor mainly via hydrophobic contacts. This fact also points towards a different orientation of the inhibitor within the active site of EGFR kinase. Binding mode analysis for CDK2 inhibition studies indicate that hydrogen bonding interaction with Lys 33 and Leu83 are important for the activity. These interactions were found to be stable throughout the simulation. Considering the results for wild-type EGFR inhibition, the docking studies on mutants were performed and which indicate that the compounds bind to the mutant EGFR but the amino acid residues involved are similar to the wild-type EGFR and therefore, the selectivity seems to be limited.

CONCLUSION

These benzamide-substituted chalcone derivatives will be useful as lead molecules for the further development of newer inhibitors of EGFR and/or CDK2 kinases.

More Than Resveratrol: New Insights into Stilbene-Based Compounds

The concept of a scaffold concerns many aspects at different steps on the drug development path. In medicinal chemistry, the choice of relevant "drug-likeness" scaffold is a starting point for the design of the structure dedicated to specific molecular targets. For many years, the chemical uniqueness of the stilbene structure has inspired scientists from different fields such as chemistry, biology, pharmacy, and medicine. In this review, we present the outstanding potential of the stilbene-based derivatives. Naturally occurring stilbenes, together with powerful synthetic chemistry possibilities, may offer an excellent approach for discovering new structures and identifying their therapeutic targets. With the development of scientific tools, sophisticated equipment, and a better understanding of the disease pathogenesis at the molecular level, the stilbene scaffold has moved innovation in science. This paper mainly focuses on the stilbene-based compounds beyond resveratrol, which are particularly attractive due to their biological activity. Given the "fresh outlook" about different stilbene-based compounds starting from stilbenoids with particular regard to isorhapontigenin and methoxy- and hydroxyl- analogues, the update about the combretastatins, and the very often overlooked and underestimated benzanilide analogues, we present a new story about this remarkable structure.

More Than Resveratrol: New Insights into Stilbene-Based Compounds

The concept of a scaffold concerns many aspects at different steps on the drug development path. In medicinal chemistry, the choice of relevant "drug-likeness" scaffold is a starting point for the design of the structure dedicated to specific molecular targets. For many years, the chemical uniqueness of the stilbene structure has inspired scientists from different fields such as chemistry, biology, pharmacy, and medicine. In this review, we present the outstanding potential of the stilbene-based derivatives. Naturally occurring stilbenes, together with powerful synthetic chemistry possibilities, may offer an excellent approach for discovering new structures and identifying their therapeutic targets. With the development of scientific tools, sophisticated equipment, and a better understanding of the disease pathogenesis at the molecular level, the stilbene scaffold has moved innovation in science. This paper mainly focuses on the stilbene-based compounds beyond resveratrol, which are particularly attractive due to their biological activity. Given the "fresh outlook" about different stilbene-based compounds starting from stilbenoids with particular regard to isorhapontigenin and methoxy- and hydroxyl- analogues, the update about the combretastatins, and the very often overlooked and underestimated benzanilide analogues, we present a new story about this remarkable structure.

Reversible Small Molecule Inhibitors of MAO A and MAO B with Anilide Motifs

BACKGROUND

Ligands consisting of two aryl moieties connected via a short spacer were shown to be potent inhibitors of monoamine oxidases (MAO) A and B, which are known as suitable targets in treatment of neurological diseases. Based on this general blueprint, we synthesized a series of 66 small aromatic amide derivatives as novel MAO A/B inhibitors.

METHODS

The compounds were synthesized, purified and structurally confirmed by spectroscopic methods. Fluorimetric enzymological assays were performed to determine MAO A/B inhibition properties. Mode and reversibility of inhibition was determined for the most potent MAO B inhibitor. Docking poses and pharmacophore models were generated to confirm the in vitro results.

RESULTS

N-(2,4-Dinitrophenyl)benzo[d][1,3]dioxole-5-carboxamide (55, ST-2043) was found to be a reversible competitive moderately selective MAO B inhibitor (IC₅₀ = 56 nM, K_i = 6.3 nM), while N-(2,4-dinitrophenyl)benzamide (7, ST-2023) showed higher preference for MAO A (IC₅₀ = 126 nM). Computational analysis confirmed in vitro binding properties, where the anilides examined possessed high surface complementarity to MAO A/B active sites.

CONCLUSION

The small molecule anilides with different substitution patterns were identified as potent MAO A/B inhibitors, which were active in nanomolar concentrations ranges. These small and easily accessible molecules are promising motifs, especially for newly designed multitargeted ligands taking advantage of these fragments.

Deciphering the mechanism of copper-catalyzed N-arylation between aryl halides and nitriles: a DFT study

The mechanism of the CuI/DMEDA-catalyzed tandem hydrolysis/N-arylation of benzonitrile with aryl iodide was studied using the DFT method.

Sustainable Synthesis and Characterization of Ni-Al-Containing Double-Layered Nanocatalysts and Their Catalytic Activity

Sustainable synthesis of Ni-Al double-layered catalysts by the coprecipitation method is described. Synthesized double-layered catalysts have been characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared, and thermogravimetric analyses, which confirmed a hydrotalcite-like structure. In addition, the impact of aging time and temperature on the activity of catalyst has been investigated. Furthermore, it has been confirmed by SEM and TEM analyses that the recovered catalyst has retained its structure. It has also been observed that the prepared material has potency to catalyze the reaction without loss in the yield. To explore the reactivity of the material, the catalyst has been examined in the synthesis of N-(2-hydroxyphenyl)benzamide under solvent-free conditions. The overall process afforded the product with high purity and high yields within short time.

Intramolecular Hydrogen Bonding Involving Organic Fluorine: NMR Investigations Corroborated by DFT-Based Theoretical Calculations

The combined utility of many one and two dimensional NMR methodologies and DFT-based theoretical calculations have been exploited to detect the intramolecular hydrogen bond (HB) in number of different organic fluorine-containing derivatives of molecules, viz. benzanilides, hydrazides, imides, benzamides, and diphenyloxamides. The existence of two and three centered hydrogen bonds has been convincingly established in the investigated molecules. The NMR spectral parameters, viz., coupling mediated through hydrogen bond, one-bond NH scalar couplings, physical parameter dependent variation of chemical shifts of NH protons have paved the way for understanding the presence of hydrogen bond involving organic fluorine in all the investigated molecules. The experimental NMR findings are further corroborated by DFT-based theoretical calculations including NCI, QTAIM, MD simulations and NBO analysis. The monitoring of H/D exchange with NMR spectroscopy established the effect of intramolecular HB and the influence of electronegativity of various substituents on the chemical kinetics in the number of organic building blocks. The utility of DQ-SQ technique in determining the information about HB in various fluorine substituted molecules has been convincingly established.

Gas-phase Smiles rearrangement reactions of deprotonated N-phenylbenzamides studied by electrospray ionization tandem mass spectrometry

RATIONALE

Electrospray ionization tandem mass spectrometry (ESI-MS(n)) is an invaluable tool for the study of gas-phase reactions. When N-phenylbenzamide is analyzed in negative ion mode, the nucleophilic deprotonated site of nitrogen or oxygen, together with the adjacent electrophilic phenyl carbon in the same molecule, provides a useful opportunity to study the intramolecular nucleophilic reaction in the gas phase.

METHODS

All MS(n) experiments of deprotonated N-phenylbenzamides were conducted on an ion trap mass spectrometer using ESI in negative ion mode. The accurate masses of fragments were measured on an ESI quadrupole time-of-flight mass spectrometer in negative ion mode. Theoretical calculations were conducted at the B3LYP/6-31++G(d,p) level of density functional theory using the Gaussian 03 program.

RESULTS

When the polarity of the substituent on the aniline ring was changed, gas-phase Smiles rearrangement reactions could be initiated by different atoms in the anionic center. Upon collisional activation, loss of CO from deprotonated N-phenylbenzamides could be observed, which can be interpreted as a nitrogen anion triggering the Smiles rearrangement reaction through a three-membered ring transition state. As the aniline ring was substituted by a strong electron-withdrawing group (e.g., NO(2), COCH(3), or CF(3)) at the para position, a characteristic phenolate anion was obtained, which was derived from the Smiles rearrangement reaction initiated by the oxygen anion through a four-membered ring transition state.

CONCLUSIONS

In the fragmentation of deprotonated N-phenylbenzamides, the gas-phase Smiles rearrangement reaction initiated by either the nitrogen or the oxygen atom can proceed. The findings in this study have not only enriched knowledge on the gas-phase Smiles rearrangement reactions, but also provided valuable information for understanding the rearrangements of deprotonated aromatic amides in gas phase.

Design and evaluation of 4-aminophenol and salicylate derivatives as free-radical scavenger

This theoretical and experimental study describes the design and evaluation of the free-radical scavenging effect for the molecular association of 4-aminophenol and salicylate derivatives. For this purpose, we employed theoretical methods for the selection of antioxidant drugs and the rapid methods of evaluation: the 1,1-diphenyl-2-picrylhydrazyl radical and the thiobarbituric acid reactive substances in the lipid peroxidation initiated by Fe(2+) and ascorbic acid in human erythrocytes. The associate derivatives exhibited a more potent inhibition than the salicylic acid, while the benzoyl compound exhibited a more potent inhibition than paracetamol. The molecular parameters related to the electron distribution and structure (ionization potential and energy of the highest occupied molecular orbital) correlated very well with the antioxidant action of the compounds studied here in different tests.

Vibrational spectroscopic studies and computational calculations of 5-chloro-2-(3-chlorophenylcarbamoyl)phenylacetate

The FT-IR and FT-Raman spectra of 5-chloro-2-(3-chlorophenylcarbamoyl)phenylacetate were studied. The vibrational wave numbers and corresponding vibrational assignments were examined theoretically using the Gaussian 03 set of quantum chemistry codes and the normal modes are assigned by Potential Energy Distribution calculations. The synthesis, elemental analysis and NMR values are presented. The red shift of the NH stretching wave number in the infrared spectrum from the computed wave number indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The first hyperpolarizability, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of nonlinear optics. The geometrical parameters of the title compound are in agreement with that of similar reported derivatives.

Relative similarity within purine nucleotide and ligand structures operating on nitric oxide synthetase, guanylyl cyclase and potassium (K ATP, BK Ca) channels

OBJECTIVES

Purine nucleotides play a central role in signal transduction events initiated at the cell membrane. The NO-cGMP-cGK pathway, in particular, mediates events involving NOS and some classes of K(+) ion channel. The aim of this study is to investigate relative molecular similarity within the ligands binding to NOS, K(ATP), BK(Ca) channels and regulatory nucleotides.

METHODS

Minimum energy conformers of the ligand structures were superimposed and fitted to L-arginine and the nucleotides of adenine and guanine using a computational program.

KEY FINDINGS

Distinctive patterns were evident in the fitting of NOS isoform antagonists to L-arginine. K(ATP) channel openers and antagonists superimposed on the glycosidic linkage and imidazole ring of the purine nucleotides, and guanidinium and ribose groups of GTP in the case of glibenclamide. The fits of BK(Ca) channel openers and antagonists to cGMP were characterized by the linear dimensions of their structures; distances between terminal oxy groups in respect of dexamethasone and aldosterone.

CONCLUSIONS

The findings provide structural evidence for the functional interaction between K(+) channel openers/antagonists and the regulatory nucleotides. Use of the purine nucleotide template systematizes the considerable heterogeneity evident within the structures of ligands operating on K(+) ion channels.

N-H...F hydrogen bonds in fluorinated benzanilides: NMR and DFT study

Using (19)F and (1)H-NMR (with (14)N decoupling) spectroscopic techniques together with density functional theoretical (DFT) calculations, we have investigated weak molecular interactions in isomeric fluorinated benzanilides. Simultaneous presence of through space nuclear spin-spin couplings ((1h)J(N-HF)) of diverse strengths and feeble structural fluctuations are detected as a function of site specific substitution of fluorine atoms within the basic identical molecular framework. The transfer of hydrogen bonding interaction energies through space is established by perturbing their strengths and monitoring the effect on NMR parameters. Multiple quantum (MQ) excitation, up to the highest possible MQ orders of coupled protons, is utilized as a tool for accurate (1)H assignments. Results of NMR studies and DFT calculations are compared with the relevant structural parameters taken from single crystal X-ray diffraction studies.

Large conductance calcium-activated potassium channels (BKCa) modulate trigeminovascular nociceptive transmission

Migraine is a common, disabling, neurological problem whose acute management would benefit from the development of purely neurally acting therapies. The trigeminocervical complex is pivotal in nociceptive signaling in migraine, and is an accepted target for putative antimigraine agents. Whole-cell patch-clamp or extracellular recordings were made of trigeminal neurons identified in rat brainstem slices. Bath application of the large conductance calcium-activated potassium (BKCa) channel opener NS1619 caused a dramatic decrease of cell firing that could be reversed by the co-application of iberiotoxin. NS1619 hyperpolarized the resting membrane potential and reduced the frequency of spontaneous action potentials in these neurons. These data suggest the presence of BKCa channels in the trigeminocervical complex. In vivo in cat L-glutamate-evoked firing was facilitated in nociceptive neurons, also responding to stimulation of the superior sagittal sinus, in the trigeminal nucleus caudalis by the BKCa peptide antagonists, iberiotoxin and slotoxin. Of units tested, 70% responded to microiontophoretic application of the blockers, identifying a subpopulation of trigeminal neurons expressing toxin-sensitive BKCa channels. NS1619 inhibited 74% of cells tested, and this was reversed by slotoxin, suggesting that the action of NS1619 in these cells was mediated through BKCa channels. These data are consistent with the presence of BKCa channels in the trigeminal nucleus caudalis that are potential targets for the development of antimigraine treatments, and may also offer insights into receptor mechanisms involved in sensitization and thus allodynia, in migraine.

BK channel activation by NS11021 decreases excitability and contractility of urinary bladder smooth muscle

Large-conductance Ca(2+)-activated potassium (BK) channels play an important role in regulating the function and activity of urinary bladder smooth muscle (UBSM), and the loss of BK channel function has been shown to increase UBSM excitability and contractility. However, it is not known whether activation of BK channels has the converse effect of reducing UBSM excitability and contractility. Here, we have sought to investigate this possibility by using the novel BK channel opener NS11021. NS11021 (3 microM) caused an approximately threefold increase in both single BK channel open probability (P(o)) and whole cell BK channel currents. The frequency of spontaneous action potentials in UBSM strips was reduced by NS11021 from a control value of 20.9 + or - 5.9 to 10.9 + or - 3.7 per minute. NS11021 also reduced the force of UBSM spontaneous phasic contractions by approximately 50%, and this force reduction was blocked by pretreatment with the BK channel blocker iberiotoxin. NS11021 (3 microM) had no effect on contractions evoked by nerve stimulation. These findings indicate that activating BK channels reduces the force of UBSM spontaneous phasic contractions, principally through decreasing the frequency of spontaneous action potentials.

Benzanilides with spasmolytic activity: chemistry, pharmacology, and SAR

The following study describes the synthesis of new benzanilide derivatives and their pharmacological investigation on smooth muscle preparations of guinea pigs. All compounds were synthesized in good yields and showed a spasmolytic activity without significant effect on vascular smooth muscles and heart muscle preparations. Moreover, further pharmacological investigations as well as in silico studies were performed to elucidate the mechanism of action. Compound 3 showed the most potent spasmolytic activity with an IC(50) of 3.25microM.

1,2,3-Triazol-carboxanilides and 1,2,3-triazol-(N-benzyl)-carboxamides as BK-potassium channel activators. XII

The chemical structures of many synthetic activators of large-conductance calcium-activated potassium channels (BK channels) satisfy a simple pharmacophore model, consisting of two appropriately substituted phenyl rings connected by a linker of a heterogeneous nature. In this paper, a series of new compounds with modifications of the linker portion of the above pharmacophore are described. In particular, in these new derivatives, the linker portion is represented by a 1,2,3-triazole-carboxamide group, which can be viewed as a combination of two different kinds of linker, independently used in previous series of BK-openers: the amide function and the 1,2,3-triazole ring. The overall finding of this study indicated that the triazole-carboxamide derivatives were generally poorly effective and that this structural modification of the linker is deleterious for activity on BK channels. Therefore, it can be hypothesized that the increase of the steric hindrance of the linker and/or the increase of the distance between the two aromatic portions are negative for the interaction with the biological target.

Synthesis, antimicrobial, and QSAR studies of substituted benzamides

A series of new substituted benzamides were synthesized and tested in vitro for their antibacterial activity against Gram-positive and Gram-negative bacteria and as well for antifungal activity. The compounds 8i and 9 showed better activity among the different benzamides synthesized. The structural characteristics governing antibacterial activities of substituted benzamides were studied using QSAR methodology. The results showed that the antimicrobial activity could be modeled using the topological descriptors, molecular connectivity indices (2chi(v) and 2chi) and Kiers shape index (kappaalpha1). The low residual activity and high cross-validated r2 values (r(cv)2) observed indicated the predictive ability of the developed QSAR models.

Functional contribution of the endothelial component to the vasorelaxing effect of resveratrol and NS 1619, activators of the large-conductance calcium-activated potassium channels

Large-conductance calcium-activated potassium channels (BK) of smooth muscle play a role in the relevant modulation of vascular tone, due to their calcium- and voltage-dependent mechanisms of activation. A potential role of endothelial BK channels has also been suggested by approaches on endothelial cell cultures. However, no functional study, aimed at evaluating the contribution of endothelial BK channels to the effect of BK-openers, has been reported. Resveratrol and NS 1619, BK-openers, have been tested on endothelium-intact and -denuded aortic rings. Furthermore, the effects of high depolarisation of potassium channel blockers TEA (Tetraethylammonium), 4-AP ( 4-Aminopyridine) and IbTX (Iberiotoxin) and of inhibitors of NO-pathway (L-NAME and ODQ) have been evaluated. The presence of endothelium increased the vasorelaxing potency of BK-openers. This potentiation was eliminated by L-NAME and ODQ. TEA, 4-AP, IbTX and high depolarisation had modest or no antagonist influence on resveratrol in endothelium-denuded aortic rings. The effects of NS 1619 on endothelium-denuded aortic rings were not affected by IbTX, and were modestly antagonised by TEA, 4-AP and high depolarisation. In intact endothelium vessels, TEA, IbTX and 4-AP antagonised the vasorelaxing effect of the two BK-activators. A BK-mediated release of endothelial NO seems a very important factor, determining a strong influence on vasodilator profile of BK-openers. Therefore, an eventual therapy with a BK-opener could promote a series of cardiovascular impacts not confined to the only direct vasorelaxing effects, but also due to a significant contribution of endothelial NO.

Structural modifications of benzanilide derivatives, effective potassium channel openers. X

Large-conductance calcium-activated potassium (BK) channels are involved in many fundamental cell functions. Consistently, the ability to activate BK channels by exogenous compounds is considered as a promising pharmacodynamic pattern for the potential treatment of several pathologies. In this perspective, the development of new and selective BK-openers can be considered as an actual field of research. This paper reports the synthesis and pharmacological evaluation of new benzanilides, useful for deepening the comprehension of the structure-activity relationships, emerged in previous studies on this class of BK-activators. From a structural point of view, these benzanilides belong to a general class of BK-activators, showing a common pharmacophoric model, consisting of two aryl groups linked through an appropriate "spacer" and the almost obligatory presence of a phenolic hydroxyl. In particular, a new series of benzanilides, in which the phenyl rings have been widely changed both on the acidic portion and the basic one of the amide spacer, were synthesised. Their vasorelaxing effects, induced through the activation of BK channels, were also evaluated. Although many compounds exhibited effects which could not be attributed to the activation of BK channels, two derivatives showed a clear profile of BK-activators with vasodilator activity comparable to or slightly lower than that recorded for the reference benzimidazolone NS1619. A further molecular modelling approach allowed us to obtain a molecular electrostatic potential feature which suggests a suitable interaction with the receptor site of the BK channel, from a tri-dimensional point of view. This approach seems to represent a further contribution for the development of new BK-activators, designed on the basis of the pharmacophoric model above-mentioned.

NMR investigation of methyl-2,4-dimethoxysalicylate: effect of solvent and temperature

(1)H NMR and (13)C NMR of methyl-2,4-dimethoxysalicylate 2 was measured in chloroform-d at the temperature range of 220-330 K, in dimethyl sulfoxide-d(6) at the temperature range of 300-400 K and in a polar protic solvent (CD(3)OD) at 300 K. The structure of 2 in liquid phase (solvent) is compared with those in solid phase (X-ray) and in the gas phase (quantum mechanical calculations). The relationship between molecular geometry, (1)H NMR chemical shift and W coupling of involved protons has a complex nature, but hydrogen bonds [C=O...H-O and C=O...H-CH(2)O] strength is the principle factor.

Heterocyclic analogs of benzanilide derivatives as potassium channel activators. IX

On the basis of our previous works, addressed to synthesise new activators of BK potassium channels, and of many suggestions from the international literature, a simple pharmacophoric model, consisting of two suitably substituted phenyl rings bound to various kinds of linkers, was hypothesised. In particular, the effectiveness of the amidic linker was demonstrated, since several benzanilide derivatives showed interesting BK-opener properties. As a development of these benzanilides, in this work we introduced heterocyclic substituents, replacing the aryl ring on the acid side or on the basic one of the amide linker of the above pharmacophore. The pharmacological results indicated some relevant remarks about the structural requirements, needed for a satisfactory BK-opener activity. In particular, the presence of a phenolic function, with a possible H-bond donor role, has been confirmed. Furthermore, the presence of nitrogen heterocycles on the acid side of the amide linker seems to be a negative requirement, while furan and thiophene were well tolerated. On the contrary, the introduction of insaturated heterocyclic rings (pyridine and thiazole) on the basic side of the amide linker, led to satisfactory biological activity, while the presence of aliphatic heterocycles lowered the pharmacological effect.

Large-conductance, calcium-activated potassium channels: structural and functional implications

The large-conductance, calcium-activated potassium channels (BK, also termed BK(Ca), Slo, or MaxiK) distributed in both excitable and non-excitable cells are involved in many cellular functions such as action potential repolarization; neuronal excitability; neurotransmitter release; hormone secretion; tuning of cochlear hair cells; innate immunity; and modulation of the tone of vascular, airway, uterine, gastrointestinal, and urinary bladder smooth muscle tissues. Because of their high conductance, activation of BK channels has a strong effect on membrane potential. BK channels differ from all other potassium (K(+)) channels due to their high sensitivity to both intracellular calcium (Ca(2+)) concentrations and voltage. These features make BK channels ideal negative feedback regulators in many cell types by decreasing voltage-dependent Ca(2+) entry through membrane potential hyperpolarization. The current review aims to give a comprehensive understanding of the structure and molecular biology of BK channels and their relevance to various pathophysiological conditions. The review will also focus on the therapeutic potential and pharmacology of the various BK channel activators and blockers.

1,4- and 2,4-substituted-1,2,3-triazoles as potential potassium channel activators. VII

New 1,4- and 2,4-substituted 1,2,3-triazole derivatives were synthesized and tested as potential BK(Ca) channel openers, as a part of a research program, which hypothesizes a pharmacophoric structure containing the 1,2,3-triazole ring. The structure-activity relationships were studied introducing some structural changes concerning molecular geometry and the presence of a hydrogen bond donor as a primary amino group and a phenolic or alcoholic hydroxy function. The compounds were prepared by nucleophilic substitution on the 1,2,3-triazole ring and by 1,3-dipolar cycloaddition of azides to selected alkynes and to phenylacetone. The new compounds tested on rat aortic rings did not exhibit any significant vasorelaxing activity.