Cytotoxicity Profiles and Neuroprotective Properties of the Novel Ifenprodil Analogues as Sigma Ligands

Neurodegeneration is a slow and progressive loss of neuronal cells or their function in specific regions of the brain or in the peripheral system. Among several causes responsible for the most common neurodegenerative diseases (NDDs), cholinergic/dopaminergic pathways, but also some endogenous receptors, are often involved. In this context, sigma 1 receptor (S1R) modulators can be used as neuroprotective and antiamnesic agents. Herein, we describe the identification of novel S1R ligands endowed with antioxidant properties, potentially useful as neuroprotective agents. We also computationally assessed how the most promising compounds might interact with the S1R protein's binding sites. The in silico predicted ADME properties suggested that they could be able to cross the brain-blood-barrier (BBB), and to reach the targets. Finally, the observation that at least two novel ifenprodil analogues (5d and 5i) induce an increase of the mRNA levels of the antioxidant NRF2 and SOD1 genes in SH-SY5Y cells suggests that they might be effective agents for protecting neurons against oxidative damage.

Synthesis, Biological Evaluation and Computational Studies of New Hydrazide Derivatives Containing 1,3,4-Oxadiazole as Antitubercular Agents

To extend our screening for novel antimycobacterial molecules, we have designed, synthesized, and biologically evaluated a library of 14 new hydrazide derivatives containing 1,3,4-oxadiazole core. A variety of mycobacterial strains, including some drug-resistant strains, were tested for antimycobacterial activity. Among the compounds tested, five showed high antimycobacterial activity (MIC values of 8 μg/mL) against M. tuberculosis H37Ra attenuated strain, and two derivatives were effective (MIC of 4 µg/mL) against pyrazinamide-resistant strains. Furthermore, the novel compounds were tested against the fungal C. albicans strain, showing no antimycotic activity, and thus demonstrating a good selectivity profile. Notably, they also exhibited low cytotoxicity against human SH-SY5Y cells. The molecular modeling carried out suggested a plausible mechanism of action towards the active site of the InhA enzyme, which confirmed our hypothesis. In conclusion, the active compounds were predicted in silico for ADME properties, and all proved to be potentially orally absorbed in humans.

Design, synthesis and biological evaluation of novel aminopropylcarboxamide derivatives as sigma ligands

In our continuing effort to develop novel sigma receptor (SR) ligands, we present the design, synthesis and binding studies of a small library of aminopropylcarboxamide derivatives, obtained from a deconstruction of the piperidine ring of previously synthesized piperidine-based compounds. The best results were achieved with benzofuran (5c, 5g) and quinoline (5a, 5e) derivatives. These compounds revealed the highest affinity for both receptor subtypes. In particular, the 3,4-dimethoxyphenyl derivatives 5e and 5g showed the highest selectivity profile for S2R, especially the quinoline derivative 5e exhibited a 35-fold higher affinity for S2R subtype. The cytotoxic activity of aforementioned compounds was evaluated against SKBR3 and MCF7 cell lines, widely used for breast cancer studies. Whereas the potency of 5g was similar that of Siramesine and Haloperidol in both cell lines, compounds 5a, 5c and 5e exhibited a potency at least comparable to that of Haloperidol in SKBR3 cells. A molecular modelling evaluation towards the S2R binding site, confirmed the strong interaction of compound 5e thus justifying its highest S2R affinity.

Synthesis, Cytotoxicity Evaluation, and Computational Insights of Novel 1,4-Diazepane-Based Sigma Ligands

Among several potential applications, sigma receptor ligands can be used as antipsychotics, antiamnesics, and against other neurodegenerative disorders as well as neuroprotective agents. We present herein a new series of diazepane-containing derivatives as σR ligands obtained by a conformational expansion approach of our previously synthesized piperidine-based compounds. The best results were reached by benzofurane 2c, 3c and quinoline 2d, 3d-substituted diazepane derivatives, which showed the highest σR affinity. The cytotoxic activities of synthesized compounds were evaluated against two cancer cell lines, and the results indicated that none of the compounds induced significant toxicity in these cells. We also evaluated the antioxidant activity by radical scavenging capacity of our best compounds on ABTS and H₂O₂. The results obtained reveal that our new derivatives possess an excellent antioxidant profile and could be protective for the cells. Overall, the benzofurane derivative 2c due to its strong interaction with the active site of the receptor, as confirmed by molecular dynamic simulations, emerged as the optimum compound with high σ1R affinity, low cytotoxicity, and a potent antioxidant activity.

Stability of a novel Lidocaine, Adrenaline and Tetracaine sterile thermosensitive gel: A ready-to-use formulation

BACKGROUND

Superficial wounds that require suturing are often the reason children visit the Paediatric Emergency Department. Suturing is usually accompanied by perilesional administration of lidocaine, a local anaesthetic drug that improves pain tolerance. In paediatric patients, this approach has a low compliance because lidocaine has to be injected, which in children generates fear and anxiety, a sterile anaesthetic gel could improve the child compliance.

OBJECTIVE

To develop a sterile and stable sterile gel capable of remaining in place over time for topical anaesthesia.

METHOD

Different formulations were analysed by HPLC, by UV and fluorimetric detection. Two different sterilisation methods were tested.

MAIN OUTCOME

To maintain the original stability of the gel also after sterilisation process.

RESULTS

Four different gels were prepared and analysed; the most stable gel lasts over 3 months with a degradation less than 10%.

CONCLUSION

The use of Poloxamer 407 guarantees stability of the preparation, showing a reduction in oxidative reaction, and gives the gel the right texture for application to a bleeding wound.

Discovery of new potent dual sigma receptor/GluN2b ligands with antioxidant property as neuroprotective agents

Among several potential applications, sigma receptors (σRs) can be used as neuroprotective agents, antiamnesic, antipsychotics and against other neurodegenerative disorders. On the other hands, antagonists of the GluN2b-subunit-containing-N-methyl-D-aspartate (NMDA) receptors are of major interest for the same purpose, being this subunit expressed in specific areas of the central nervous system and responsible for the excitatory regulation of nerve cells. Under these premises, we have synthesized and biologically tested novel hybrid derivatives obtained from the combination of phenyloxadiazolone and dihydroquinolinone scaffolds with different amine moieties, peculiar of σ2R ligands. Most of the new ligands exhibited a pan-affinity towards both σR subtypes and high affinity against GluN2b subunit. The most promising compounds belong to the dihydroquinolinone series, with the best affinity profile for the cyclohexylpiperazine derivative 28. Investigation on their biological activity showed that the new compounds were able to protect SH-SY5Y cells against oxidative stress induced by hydrogen peroxide treatment. These results proved that our dual σR/GluN2b ligands have beneficial effects in a model of neuronal oxidative stress and can represent strong candidate pharmacotherapeutic agents for minimizing oxidative stress-induced neuronal injuries.

PEGylation of coenzyme Q10 and in vitro release studies

Methoxy polyethylene glycol conjugated with coenzyme Q10 (mPEG)-CoQ10 and analog adducts with amino acids as spacers were synthesized as a new drug delivery systems for CoQ10. Alanine and branched chain amino acids (valine, leucine and isoleucine) were conjugated to mPEG by an amide linkage and to CoQ10 by an ester bond. Recently, branched chain amino acids (BCAAs), which are released along with CoQ10, have received increasing attention as 'anti-fatigue' elements. FT-IR and 1H NMR spectroscopic analysis were useful to characterize the synthesized conjugates. Studies in vitro, in buffer solutions at different pH and in the presence of esterase were conducted. The hydrolysis studies showed a specific cleavage dependent on the pH of the medium and by the presence of proteolytic enzymes. The results showed the improvement of the pharmacokinetic properties of CoQ10. The antioxidant activity of the synthesized conjugates was also evaluated by DPPH assay.

Improving selectivity preserving affinity: new piperidine-4-carboxamide derivatives as effective sigma-1-ligands

We report the design, synthesis and binding evaluation against σ1 and σ2 receptors of a series of new piperidine-4-carboxamide derivatives variously substituted on the amide nitrogen atom. Specifically, we assessed the effects exerted on σ receptor affinity by substituting the N-benzylcarboxamide group present on a series of compounds previously synthesized in our laboratory with different cyclic or linear moieties. The synthesized compounds 2a-o were tested to estimate their affinity and selectivity toward σ1 and σ2 receptors. Very high σ1 affinity (Ki = 3.7 nM) and Kiσ2/Kiσ1 selectivity ratio (351) were found for the tetrahydroquinoline derivative 2k, featuring a 4-chlorobenzyl moiety linked to the piperidine nitrogen atom.

Synthesis and receptor binding studies of some new arylcarboxamide derivatives as sigma-1 ligands

We describe here the synthesis and the binding interaction with σ1 and σ2 receptors of a series of new arylcarboxamide derivatives variously substituted on the aromatic portions. Maintaining a partial scaffold of a series of compounds previously synthesized by us, we evaluate the effect of the substitution on σ binding. The synthesized compounds have been tested to estimate their affinity and selectivity toward σ1 and σ2 receptors. Two out of 16 derivatives showed an interesting σ1 affinity (21.2 and 13.6 nM-compounds 2m and 2p) and a good selectivity (Ki(σ2)/Ki(σ1) >140 and >40, respectively).

Another brick in the wall. Validation of the σ1 receptor 3D model by computer-assisted design, synthesis, and activity of new σ1 ligands

Originally considered an enigmatic polypeptide, the σ(1) receptor has recently been identified as a unique ligand-regulated protein. Many studies have shown the potential of σ(1) receptor ligands for the treatment of various diseases of the central nervous system (CNS); nevertheless, almost no information about the 3D structure of the receptor and/or the possible modes of interaction of the σ(1) protein with its ligands have been unveiled so far. With the present work we validated our σ(1) 3D homology model and assessed its reliability as a platform for σ(1) ligand structure-based drug design. To this purpose, the 3D σ(1) model was exploited in the design of 33 new σ(1) ligands and in their ranking for receptor affinity by extensive molecular dynamics simulation-based free energy calculations. Also, the main interactions involved in receptor/ligand binding were analyzed by applying a per residue free energy deconvolution and in silico alanine scanning mutagenesis calculations. Subsequently, all compounds were synthesized in our laboratory and tested for σ(1) binding activity in vitro. The agreement between in silico and in vitro results confirms the reliability of the proposed σ(1) 3D model in the a priori prediction of the affinity of new σ(1) ligands. Moreover, it also supports and corroborates the currently available biochemical data concerning the σ(1) protein residues considered essential for σ(1) ligand binding and activity.

Homology Model and Docking-Based Virtual Screening for Ligands of the σ1 Receptor

This study presents for the first time the 3D model of the σ1 receptor protein as obtained from homology modeling techniques, shows the applicability of this structure to docking-based virtual screening, defines a computational strategy to optimize the results based on a combination of 3D pharmacophore-based docking and MM/PBSA free energy of binding scoring, and provides evidence that these in silico models and recipes are powerful tools on which virtual screening of new σ1 ligands can be based. In particular, the validation of the applicability of docking-based virtual screening to homology models is of utmost importance, since no crystal structure is available to date for the σ1 receptor, and this missing information still constitutes a major hurdle for a rational ligand design for this important protein target.

Synthesis, biological evaluation, and three-dimensional in silico pharmacophore model for sigma(1) receptor ligands based on a series of substituted benzo[d]oxazol-2(3H)-one derivatives

Novel benzo[d]oxazol-2(3H)-one derivatives were designed and synthesized, and their affinities against sigma receptors were evaluated. On the basis of 31 compounds, a three-dimensional pharmacophore model for the sigma(1) receptor binding site was developed using the Catalyst 4.9 software package. The best 3D pharmacophore hypothesis, consisting of one positive ionizable, one hydrogen bond acceptor, two hydrophobic aromatic, and one hydrophobic features provided a 3D-QSAR model with a correlation coefficient of 0.89. The best hypothesis was also validated by three independent methods, i.e., the Fisher randomization test included in the CatScramble functionality of Catalyst, the leave-one-out test, and activity prediction of an additional test set. The achieved results will allow researchers to use this 3D pharmacophore model for the design and synthesis of a second generation of high affinity sigma(1) ligands, as well as to discover other lead compounds for this class of receptors.

Substituted benzo[d]oxazol-2(3H)-one derivatives with preference for the sigma1 binding site

We describe here the synthesis and the binding interaction with sigma(1) and sigma(2) receptors of a series of new benzo[d]oxazol-2(3H)-one derivatives variously substituted on the N-benzyl moiety. The results of binding studies confirm the notion that the benzoxazolone moiety confers preference towards sigma(1) sites and establish that the ability to bind to sigma(1), but not to sigma(2) receptors, is strongly affected by the kind and the position of the substituents introduced in the N-benzyl ring. In fact, compounds with substitutions in para-position with atoms of Cl, H or F or with a CH(3) group exhibit a higher affinity for sigma(1) receptors than the corresponding ortho-substituted compounds. The highest affinity and selectivity, with K(i) values of 0.1 and 427 nM for sigma(1) and sigma(2) receptors, respectively, and a corresponding K(i)sigma(2)/K(i)sigma(1) selectivity ratio of 4270 were found for the Cl-substituted compound. These results indicate that benzo[d]oxazol-2(3H)-one derivatives are among the most selective and sigma(1) receptor-preferring ligands currently available.

Antifungal and antimycobacterial activity of 1-(3,5-diaryl-4,5-dihydro-1H-pyrazol-4-yl)-1H-imidazole derivatives

1-(3,5-Diaryl-4,5-dihydro-1H-pyrazol-4-yl)-1H-imidazole derivatives were synthesized and tested for their in vitro antifungal and antimycobacterial activities. These imidazole derivatives showed an excellent antifungal activity against a clinical strain of Candida albicans and an interesting antitubercular activity against Mycobacterium tuberculosis H(37)Rv reference strain.

Synthesis, antifungal and antimycobacterial activities of new bis-imidazole derivatives, and prediction of their binding to P45014DM by molecular docking and MM/PBSA method

New bis-imidazole derivatives have been synthesized and their antifungal and antimycobacterial activity was determined. Almost all compounds exhibited a moderate to good activity against two clinical isolates of Candida albicans 3038 and Candida glabrata 123. The same compounds showed an interesting killing activity against Mycobacterium tuberculosis H(37)Rv reference strain. Docking procedures combined with molecular dynamics simulations in the MM/PBSA framework of theory were applied to predict the binding mode of all compounds in the binding pocket of the cytochrome P450 14alpha-sterol demethylase (14DM) of C. albicans, for which no ligand-protein crystal structure is currently available. The results obtained in silico showed that the active compounds may interact at the active site of protein, and that their binding free energy values are in agreement with the corresponding experimental activity values.

Substituted benzylaminoalkylindoles with preference for the sigma2 binding site

In the attempt to develop new sigma ligands we synthesized a series of N-benzyl-3-[1-(4-fluorophenyl)-1H-indol-3-yl]-N-methylpropan-1-amines and N-benzyl-4-[1-(4-fluorophenyl)-1H-indol-3-yl]-N-methylbutan-1-amines variously substituted on the phenyl ring. The displacement percentages of [3H]-DTG and [3H]-(+)-pentazocine determined in rat liver homogenates by these compounds at the fixed 100 nM concentration have been determined as a preliminary evaluation of their sigma1 and sigma2 affinity, respectively. The results suggested that the phenyl substituents may positively modulate, in comparison with the unsubstituted compound, the ability to displace [3H]-DTG from sigma2 sites, whereas the same phenyl substituents reduced the displacement percentages of [3H]-(+)-pentazocine from sigma1 sites. Some of these compounds were selected for radioligand binding assays. Compounds with a butylene intermediate chain displayed the greatest binding affinity for sigma2 over sigma1 receptors. The butylene derivative with 2,4-dimethyl substitution on the phenyl ring showed the greatest sigma2 affinity (sigma2Ki=5.9 nM) and an appreciable sigma2 over sigma1 selectivity (sigma1Ki/sigma2Ki=22). The obtained results suggest that a butylene chain separating the indole moiety from variously substituted benzylamino groups may be required to their interaction with a hypothetical secondary sigma2 binding site.

Enantioselective chromatography and absolute configuration of N,N-dimethyl-3-(naphthalen-2-yl)-butan-1-amines: potential sigma1 ligands

We describe the preparation of racemic N,N-dimethyl-3-(naphthalen-2-yl)-butan-1-amines, potential sigma1 ligands, and their resolution via chiral HPLC. In order to obtain enantiopure compounds, direct chromatographic methods of separation using chiral stationary phases were investigated. Different methods suitable for both analytical and semipreparative purposes are proposed. The best resolutions were achieved using cellulose tris (3,5-dimethylphenyl carbamate) (Chiralcel OD and OD-H) and amylose tris (3,5-dimethylphenyl carbamate) (Chiralpak AD). On the basis of the preliminary chromatographic results, the resolution of compound 1 was transferred onto a Chiralcel OD semipreparative column. The enantiomers were obtained in high enantiomeric excess. The configurational assignment was performed by circular dichroism. Computational analysis was used to explore the enantioselective recognition process of compound 1 with the Chiralcel OD stationary phase.

Antifungal and antimycobacterial activity of new imidazole and triazole derivatives. A combined experimental and computational approach

OBJECTIVES

To synthesize new antimycobacterial and antifungal drugs that act by binding to sterol 14alpha-demethylase (14DM) and to characterize the drug-target protein interactions using computer-based molecular simulations.

METHODS

Different series of imidazole and triazole derivatives having an azomethine linkage to pyridine 2-carboxamidrazone were designed and synthesized. Molecular dynamic simulations of the sterol 14DM (a mixed-function oxidase involved in sterol synthesis in eukaryotic and prokaryotic organisms) complexed with new azole derivatives have been performed to both qualify and quantify the protein-ligand interactions. MICs of the compounds were evaluated by reference assay and by the recently developed Microdilution Resazurin Assay (MRA).

RESULTS

Halogenated derivatives showed good activity, with an MIC90 of 1 mg/L against 33 Candida spp. clinical strains; most compounds also had inhibitory activity against Mycobacterium tuberculosis reference and clinical strains, with MICs in the range 4-64 mg/L. Molecular modelling investigations showed that the active new compounds may interact at the active site of both the fungal and the mycobacterial cytochrome P450-dependent sterol-14alpha-demethylase and that the calculated binding free energy values are in agreement with the corresponding MIC values.

CONCLUSIONS

The combined experimental and computational approach can be helpful in targeted drug design, thus yielding valuable information for the synthesis and prediction of activity of a second generation of inhibitors.

Antimycobacterial activity of new 3-substituted 5-(pyridin-4-yl)-3H-1,3,4-oxadiazol-2-one and 2-thione derivatives. Preliminary molecular modeling investigations

3H-1,3,4-Oxadiazole-2-thione and 3H-1,3,4-oxadiazol-2-one derivatives were synthesized and tested for their in vitro antimycobacterial activity. Oxadiazolone derivatives showed an interesting antimycobacterial activity against the tested strain of Mycobacterium tuberculosis H(37)Rv, whereas the corresponding thione derivatives were devoid of activity. Molecular modeling investigations showed that the active compounds may interact at the active site of the mycobacterial cytochrome P450-dependent sterol 14alpha-demethylase in the sterol biosynthesis pathway and that their binding free energy values are in agreement with their MIC values.

Synthesis and antimycobacterial activity of (3,4-diaryl-3H-thiazol-2-ylidene)-hydrazide derivatives

[5-(pyridin-2-yl)-1,3,4-thiadiazol-2-ylthio]acetic acid (3,4-diaryl-3H-thiazol-2-ylidene)-hydrazide derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed an interesting activity against a strain of Mycobacterium tuberculosis H(37)Rv and three clinical isolates of M. tuberculosis.

Synthesis and antifungal activity of (+/-)-1-(5-aryl-3-pyridin-2-yl-4,5-dihydro-pyrazol-1-yl)-2-imidazol-1-yl-ethanone derivatives

(+/-)-1-(5-Aryl-3-pyridin-2-yl-4,5-dihydro-pyrazol-1-yl)-2-imidazol-1-yl-ethanone derivatives were synthesized and tested for their in vitro antifungal activity. The compounds showed a moderate activity against strains of Candida parapsilosis, Candida pseudotropicalis and Candida glabrata.

Antimycobacterial activity of N1-[1-[3-aryl-1-(pyridin-2-, 3- or 4-yl)-3-oxo] propyl]-2-pyridinecarboxamidrazones

Infections caused by non-tuberculous mycobacteria and multidrug-resistant Mycobacterium tuberculosis are difficult to treat, and so new compounds potentially active against these bacteria are being sought. A series of 2-pyridinecarboxamidrazone derivatives, recently synthesized, have been evaluated for their inhibitory activity against 17 Mycobacterium avium isolates; the agar dilution method showed different degrees of susceptibility to the new molecules. Four molecules, three of which are chlorine derivatives, inhibited 94% of the strains tested with an MIC of 32 mg/L. These data indicate that these new pyridine-2-carboxamidrazones merit further study as antimycobacterial agents.

Synthesis and antimycobacterial activity of [5-(pyridin-2-yl)-1,3,4-thiadiazol-2-ylthio]acetic acid arylidene-hydrazide derivatives

[5-(Pyridin-2-yl)-1,3,4-thiadiazol-2-ylthio]acetic acid arylidene-hydrazide derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed a feable activity against a strain of Mycobacterium tuberculosis and a strain of Mycobacterium avium.

Synthesis and antimycobacterial activity of 5-aryl-1-isonicotinoyl-3-(pyridin-2-yl)-4, 5-dihydro-1H-pyrazole derivatives

5-Aryl-1-isonicotinoyl-3-(pyridin-2-yl)-4,5-dihydro-1H-pyrazole derivatives were synthesized and tested for their in vitro antimycobacterial activity. The compounds showed an interesting activity against a strain of Mycobacterium tuberculosis and a human strain of M. tuberculosis H4.

Synthesis and antimycobacterial activity of some 4H-1,2,4-triazin-5-one derivatives

6-[(Arylmethylenamino)carbonyl]-3-(pyridin-2-yl)-4H-1,2,4-triazin-5-one derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed interesting activity against a strain of Mycobacterium tuberculosis.

Synthesis and antimycobacterial activity of some N1-[1-[3-aryl-1-(pyridin-2-, 3-, or 4-yl)-3-oxo]propyl]-2- pyridinecarboxamidrazones

N1-[1-[3-aryl-1-(pyridin-2,3-, and 4-yl)-3-oxo[propyl]-2- pyridinecarboxamidrazone derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed interesting activity against a strain of Mycobacterium tuberculosis and a strain of Mycobacterium avium.

Synthesis and antimicrobial activity of some 2,5-disubstituted 1,3,4,-thiadiazole derivatives

A series of 5-substituted 2-arylamino-1,3,4-thiadiazole derivatives was prepared. The antimicrobial activity of these compounds against some strains of bacteria and a strain of Candida albicans was determined, together with that of the corresponding thiosemicarbazone derivatives, which are intermediates in the synthetical procedure.

Synthesis and antimycobacterial activity of some indole derivatives of pyridine-2-carboxamidrazone and quinoline-2-carboxamidrazone

A series of pyridine-2-carboxamidrazone and quinoline-2-carboxamidrazone derivatives containing the indole moiety was prepared. Some of the synthesized compounds showed an interesting in vitro antimycobacterial activity against a strain of Mycobacterium tuberculosis.

In-vitro antimycobacterial activity of new synthetic amidrazone derivatives

After preliminary in vitro screening of 15 newly synthesized compounds belonging to the chemical class of N1-(aryliden)-4-pyridinecarboxyamidrazones against Mycobacterium tuberculosis reference strain H37 Rv, we determined the minimum inhibitory concentrations (MICs) of the six most promising chemicals against different species of Mycobacterium and different strains of M. tuberculosis. The agar dilution method was employed against M. gordonae, M. bovis, M. kansasi, M. avium, M. fortuitum and on eighteen different strains of M. tuberculosis, isolated from human bronchial aspirates. The results obtained confirmed that the newly synthesized chemicals possessed a very interesting antitubercular activity, their MICs ranging from 4 micrograms/ml to 16 micrograms/ml.

Synthesis and antimycobacterial activity of some 4-pyridinecarboxyamidrazone derivatives

A series of N1-aryliden-4-pyridinecarboxyamidrazone derivatives was prepared. Some of the synthesized compounds showed interesting in vitro antimycobacterial activity against some strains of Mycobacterium and clinical isolates of Mycobacterium tuberculosis.

Simultaneous determination of amiodarone and desethylamiodarone in human plasma by high performance liquid chromatography

A rapid, sensitive and specific reversed phase HPLC method for the simultaneous assay of amiodarone and its major metabolite desethylamiodarone in human serum has been developed. This method is suitable for pharmacokinetic studies and for monitoring of the drug and metabolite concentrations in serum of patients on both short and long-term therapy with amiodarone.

Preliminary evaluation of in-vitro antimycobacterial properties of N1-(aryliden)-2-pyridinecarboxyamidrazones

After preliminary in vitro screening of 17 newly synthesized compounds belonging to the chemical class of N1-(aryliden)-2-pyridinecarboxyamidrazones, active against Mycobacterium tuberculosis H37Rv, the minimum inhibitory concentrations (MICs) of the ten most promising agents against three clinical isolates were determined by agar dilution. Compounds 12 and 14 were the most active, each inhibiting strain H37Rv at concentrations of 8 microg/ml and having a MIC of 16 microg/ml against the human isolates. The results obtained in this preliminary study confirmed the interesting antitubercular properties of these newly synthesized compounds and allowed us to carry out our investigations over a large number of isolated clinical strains.

Synthesis and antifungal activity of some amidrazone derivatives

The synthesis and in vitro antifungal activity of some pyridincarboxyamidrazone derivatives are described. 2-pyridincarboxyamidrazone derivative (IIa) in comparison with miconazole showed an interesting even if low antimycotic activity.

Synthesis and antihypertensive activity of some 1,3,4-thiadiazole derivatives

A series of 2-arylamino-1,3,4-thiadiazole derivatives was synthesized with the aim to find new antihypertensive compounds. The antihypertensive activity of some of these compounds was examined intraperitoneally in conscious spontaneously hypertensive rats (SHR). The tested compounds showed activity, but none of these possessed a higher potency than the reference substance guanabenz.

Antihypertensive activity of arylidenaminoguanidine derivatives

The synthesis of new benzylidenaminoguanidine compounds is described. Some of these compounds were tested for antihypertensive activity in conscious unrestrained spontaneously hypertensive rats. The compounds examined possess a significant antihypertensive activity, qualitatively different from that of clonidine. For the tested compounds, the absence of the transient rise in blood pressure, which appears immediately after administration of clonidine-like drugs, is noteworthy.

Simultaneous quantitation of paracetamol, caffeine and propyphenazone by high-pressure liquid chromatography

A reversed-phase high-performance liquid chromatographic method has been developed to determine paracetamol, caffeine and propyphenazone in a typical tablet formulation with high accuracy and precision. The mobile phase is a linear water-methanol gradient.

Ion-pair liquid chromatographic assay of angiotensin-converting enzyme activity

A rapid and specific high-performance liquid chromatographic assay for the quantitative determination of angiotensin-converting enzyme activity is described. Hippuryl-L-histidyl-L-leucine (Hip-His-Leu) is used as substrate and the released hippuric acid is measured. The procedure is accurate and precise and no extraction is required.