Synthesis and antimicrobial activity of thiosemicarbazides, s-triazoles and their Mannich bases bearing 3-chlorophenyl moiety

Bifunctional antimicrobial conjugates and hybrid antimicrobials

Covering: up to the end of 2016Novel antimicrobial drugs are continuously needed to counteract bacterial resistance development. An innovative molecular design strategy for novel antibiotic drugs is based on the hybridization of an antibiotic with a second functional entity. Such conjugates can be grouped into two major categories. In the first category (antimicrobial hybrids), both functional elements of the hybrid exert antimicrobial activity. Due to the dual targeting, resistance development can be significantly impaired, the pharmacokinetic properties can be superior compared to combination therapies with the single antibiotics, and the antibacterial potency is often enhanced in a synergistic manner. In the second category (antimicrobial conjugates), one functional moiety controls the accumulation of the other part of the conjugate, e.g. by mediating an active transport into the bacterial cell or blocking the efflux. This approach is mostly applied to translocate compounds across the cell envelope of Gram-negative bacteria through membrane-embedded transporters (e.g. siderophore transporters) that provide nutrition and signalling compounds to the cell. Such 'Trojan Horse' approaches can expand the antibacterial activity of compounds against Gram-negative pathogens, or offer new options for natural products that could not be developed as standalone antibiotics, e.g. due to their toxicity.

Novel Concept of Discrimination of 1,2,4-Triazole-3-thione and 3-Thiol Tautomers

Till now, three major spectroscopic techniques, fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography, have been used for determination of thiol-thione tautomeric forms. Therefore, a novel analytical concept of discrimination of 1,2,4-triazole-3-thione and 3-thiol tautomers using two high-resolution mass spectrometers has been proposed. It comprises the high-performance liquid chromatography (HPLC) hyphenated with electrospray ionization (ESI)-time-of-flight mass spectrometry (ESI-TOF-MS, positive ion mode) followed by in-source collision-induced dissociation (CID) and low-energy CID-tandem mass spectrometry (MS/MS) analysis measured with a Quadruple-TOF-MS instrument. The HPLC column was a Zorbax Stable Bond RP-18 and a rapid isocratic elution. Selected 3-thione and 3-thiol tautomers were rapidly separated, within 6 min and detected both by in-source CID ESI(+)-TOF-MS and CID ESI(+)-QTOF-MS with a high mass accuracy and high sensitivity. The method limits of detection were of 2.8-5.6 pg/μl (at S/N 3:1) for ESI-TOF-MS and 0.25-0.55 pg/μl for ESI-QTOF-MS. The tautomeric form could be easily discriminated by both methods and by the different gas-phase fragmentation patterns. Differences and similarities between in-source CID MS and CID MS/MS spectra have also been presented. These findings were also supported by recorded FT-IR spectra in solid state. The developed methodology using both the high-resolution MS systems is considerably the most sensitive among the others.

Hybrid antibiotics - clinical progress and novel designs

INTRODUCTION

There is a growing need for new antibacterial agents, but success in development of antibiotics in recent years has been limited. This has led researchers to investigate novel approaches to finding compounds that are effective against multi-drug resistant bacteria, and that delay onset of resistance. One such strategy has been to link antibiotics to produce hybrids designed to overcome resistance mechanisms.

AREAS COVERED

The concept of dual-acting hybrid antibiotics was introduced and reviewed in this journal in 2010. In the present review the authors sought to discover how clinical candidates described had progressed, and to examine how the field has developed. In three sections the authors cover the clinical progress of hybrid antibiotics, novel agents produced from hybridisation of two or more small-molecule antibiotics, and novel agents produced from hybridisation of antibiotics with small-molecules that have complementary activity.

EXPERT OPINION

Many key questions regarding dual-acting hybrid antibiotics remain to be answered, and the proposed benefits of this approach are yet to be demonstrated. While Cadazolid in particular continues to progress in the clinic, suggesting that there is promise in hybridisation through covalent linkage, it may be that properties other than antibacterial activity are key when choosing a partner molecule.

Design, Synthesis and Evaluation of Triazole-Pyrimidine Analogues as SecA Inhibitors

SecA, a key component of the bacterial Sec-dependent secretion pathway, is an attractive target for the development of new antimicrobial agents. Through a combination of virtual screening and experimental exploration of the surrounding chemical space, we identified a hit bistriazole SecA inhibitor, SCA-21, and studied a series of analogues by systematic dissections of the core scaffold. Evaluation of these analogues allowed us to establish an initial structure-activity relationship in SecA inhibition. The best compounds in this group are potent inhibitors of SecA-dependent protein-conducting channel activity and protein translocation activity at low- to sub-micromolar concentrations. They also have minimal inhibitory concentration (MIC) values against various strains of bacteria that correlate well with the SecA and protein translocation inhibition data. These compounds are effective against methicillin-resistant Staphylococcus aureus strains with various levels of efflux pump activity, indicating the capacity of SecA inhibitors to null the effect of multidrug resistance. Results from studies of drug-affinity-responsive target stability and protein pull-down assays are consistent with SecA as a target for these compounds.

Biological evaluation and molecular modelling study of thiosemicarbazide derivatives as bacterial type IIA topoisomerases inhibitors

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC(50) below 15 μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32 μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.

Unveiling the Mode of Action of Two Antibacterial Tanshinone Derivatives

In this study, 2-(N-pyrrolidine-alkyl) tanshinones bearing pyrrolidine groups were synthesized and the antibacterial mechanism was explored. These derivatives selectively elicited antibacterial activity against Gram-positive bacteria. Moreover, their antibacterial activities were time-, concentration-dependent and persistent. It appeared that Fenton-mediated hydroxyl radicals were involved, and the disruption of cell membranes was observed. This study indicates that 2-(N-pyrrolidine-alkyl) tanshinones might be potential candidates as antibacterial agents.

Structural, spectral, thermal and biological studies on (Z)-N-benzoyl-N'-(2-oxo-2-(phenylamino)acetyl)carbamohydrazonothioic acid (H₂PABT) and its Cd(II), Hg(II), Zn(II) and U(VI)O₂²⁺ complexes

A new metal complexes formed by the reaction of (Z)-N-benzoyl-N'-(2-oxo-2-(phenylamino)acetyl)carbamohydrazonothioic acid (H2PABT) and Cd(II), Hg(II), Zn(II) and U(VI)O2(2+) ions. The isolated complexes were prepared and characterized by conventional techniques. The IR data revealed that the ligand behaves as mononegative tridentate in Zn(II) and U(VI)O2(2+) complexes also, binegative tetradentate on Cd(II) and Hg(II) complexes. On the basis of magnetic and electronic spectral data an octahedral geometry for the U(VI)O2(2+) complex, a tetrahedral structure for the Cd(II), Zn(II) and Hg(II) complexes have been proposed. The IR spectrum of ligand which determined experimentally is compared with those obtained theoretically from DFT calculations. Also, the bond lengths, bond angles, HOMO, LUMO and dipole moments have been calculated. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the ligand molecules. The calculated values of binding energies indicates the stability of complexes is higher that of ligand. Also, the kinetic and thermodynamic parameters for the different thermal degradation steps of the complexes were determined by Coats-Redfern and Horowitz-Metzger methods. Moreover, the ligand and its complexes were screened against Bacillus subtilis as Gram positive bacteria and Escherichia coli Gram negative bacteria using the inhibitory zone diameter. Also the antitumor activities of the ligand and its complexes have been evaluated against liver (HePG2) and breast (MCF-7) cancer cells. Out of all the synthesized compounds, [Hg2(PABT)Cl2(H2O)2] and [(UO2)(HPABT)(OAc)(H2O)] complexes showed high antibacterial activity with 55.5% while H2PABT showed the best cytotoxic effect on liver and breast cancer cells with IC50 2.10 and 5.91 of cytotoxicity respectively.

Design, synthesis and biological evaluation of 4-benzoyl-1-dichlorobenzoylthiosemicarbazides as potent Gram-positive antibacterial agents

Twelve 4-benzoyl-1-dichlorobenzoylthiosemicarbazides have been tested as potential antibacterials. All the compounds had MICs between 0.49 and 15.63 µg/ml toward Micrococcus luteus, Bacillus cereus, Bacillus subtilis and Staphylococcus epidermidis indicating, in most cases, equipotent or even more effective action than cefuroxime. In order to clarify if the observed antibacterial effects are universal, further research were undertaken to test inhibitory potency of two most potent compounds 3 and 11 on clinical isolates of Staphylococcus aureus. Compound 11 inhibited the growth of methicillin-sensitive S. aureus (MSSA) at MICs of 1.95-7.81 µg/ml, methicillin-resistant S. aureus (MRSA) at MICs of 0.49-1.95 µg/ml and MDR-MRSA at MIC of 0.98 and 3.90 µg/ml, respectively. Finally, inhibitory efficacy of 3 and 11 on planktonic cells and biofilms formation in clinical isolates of S. aureus and Haemophilus parainfluenzae was tested. The majority of cells in biofilm populations of MSSA and MRSA were eradicated at low level of 3, with MBICs in the range of 7.82-15.63 µg/ml.

Synthesis and biological evaluation of pyrazolylthiazole carboxylic acids as potent anti-inflammatory-antimicrobial agents

Current Letter presents design, synthesis and biological evaluation of a novel series of pyrazolylthiazole carboxylates 1a-1p and corresponding acid derivatives 2a-2p. All 32 novel compounds were tested for their in vivo anti-inflammatory activity by carrageenan-induced rat paw edema method as well as for in vitro antimicrobial activity. All the tested compounds exhibited excellent AI activity profile. Three compounds 1p (R=Cl, R(1)=Cl), 2c (R=H, R(1)=F) and 2n (R=Cl, R(1)=OCH3) were identified as potent anti-inflammatory agents exhibiting edema inhibition of 93.06-89.59% which is comparable to the reference drug indomethacin (91.32%) after 3h of carrageenan injection while most of the other compounds displayed inhibition ⩾80%. In addition, pyrazolylthiazole carboxylic acids (2a-2p) also showed good antimicrobial profile. Compound 2h (R=OCH3, R(1)=Cl) showed excellent antimicrobial activity (MIC 6.25μg/mL) against both Gram positive bacteria comparable with the reference drug ciprofloxacin (MIC 6.25μg/mL).

RP-HPLC analysis and in vitro identification of antimycobacterial activity of novel thiosemicarbazides and 1,2,4-triazole derivatives

It has been widely recognized that chromatography can be applied to derive parameters useful for anticipation of the pharmacological properties of xenobiotics. The purpose of this study was to evaluate the use of C18 stationary phase in chromatographic experiments as to assess antimycobacterial activity of series of novel thiosemicarbazides and their cyclization products: 1,2,4-triazole derivatives. Chromatographically determined lipophilicity descriptors log k(w), S and φ0 and computer generated molecular descriptors were obtained for 32 compounds and Rifampicin as a representative anti-tuberculosis drug. As experimental parameters were not significantly related to the calculated values, the data were analyzed by the principal component analysis PCA allowing for the extraction of "dipole moment" and "energy due to solvation" as the most powerful parameters from large set of diverse data. The approach ranked the examined analytes as active and inactive against Mycobacterium strains. More significant clustering of examined compounds was achieved by construction of 3D graph relating computational (dipole moment, energy due to solvation) and experimental log k(w) (MeOH) descriptors. It was proved that lack of substituent in the C5 position in the triazole ring appears to be characteristic for active derivatives. Provided conclusions can be taken into account in planning further synthesis of new derivatives with antimycobacterial activity.

Mannich bases in medicinal chemistry and drug design

The biological activity of Mannich bases, a structurally heterogeneous class of chemical compounds that are generated from various substrates through the introduction of an aminomethyl function by means of the Mannich reaction, is surveyed, with emphasis on the relationship between structure and biological activity. The review covers extensively the literature reports that have disclosed Mannich bases as anticancer and cytotoxic agents, or compounds with potential antibacterial and antifungal activity in the last decade. The most relevant studies on the activity of Mannich bases as antimycobacterial agents, antimalarials, or antiviral candidates have been included as well. The review contains also a thorough coverage of anticonvulsant, anti-inflammatory, analgesic and antioxidant activities of Mannich bases. In addition, several minor biological activities of Mannich bases, such as their ability to regulate blood pressure or inhibit platelet aggregation, their antiparasitic and anti-ulcer effects, as well as their use as agents for the treatment of mental disorders have been presented. The review gives in the end a brief overview of the potential of Mannich bases as inhibitors of various enzymes or ligands for several receptors.

Bis-imidazolium and benzimidazolium based gemini-type ionic liquids structure: synthesis and antibacterial evaluation

The incorporated benzenesulfonamide moiety and the active side substituents in di-imidazolium and benzimidazolium cations enhanced both antibacterial activity and miscibility for the synthesized gemini type ILs.

L-Proline catalyzed one-step synthesis of 4,5-diaryl-2H-1,2,3-triazoles from heteroaryl cyanostilbenes via [3+2] cycloaddition of azide

Use of a novel reagent has been established for the synthesis of a series of 4,5-diaryl-2H-1,2,3-triazoles (6a-i and 9a-e) from cyanostilbene analogs of benzo[b]thiophene, benzo[b]furan and indole, catalyzed by L-proline via Lewis base-catalyzed one-step [3+2]cycloaddition of azide. This method provides an efficient, simple and environmentally benign procedure that affords good yields and relatively short reaction times.

Studies on the anticonvulsant activity and influence on GABA-ergic neurotransmission of 1,2,4-triazole-3-thione- based compounds

The anticonvulsant activity of several 1,2,4-triazole-3-thione derivatives on mouse maximal electroshock-induced seizures was tested in this study. Characteristic features of all active compounds were rapid onset of action and long lasting effect. Structure-activity observations showed that the probability of obtaining compounds exerting anticonvulsant activity was much higher when at least one of the phenyl rings attached to 1,2,4-triazole nucleus had a substituent at the para position. The obtained results, moreover, permit us to conclude that despite the structural similarity of loreclezole (second-generation anticonvulsant drug) and the titled compounds, their anticonvulsant activity is achieved via completely different molecular mechanisms.

Structure-activity relationship studies of microbiologically active thiosemicarbazides derived from hydroxybenzoic acid hydrazides

Forty-five derivatives of thiosemicarbazide were synthesized, and their antibacterial activity against Gram-positive and Gram-negative bacteria was evaluated. Some of the described compounds exhibited interesting activity against reference strains of Gram-positive bacteria, whereas only two derivatives had the ability to inhibit the growth of Gram-negative species (Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, Proteus mirabilis ATCC 12453). The most potent antimicrobial activity was observed in the cases of salicylic acid hydrazide derivatives. The differences in activity inspired us to conduct conformational analysis using molecular mechanics level. The obtained results suggest that the molecule geometry, especially at the N4-terminus of thiosemicarbazide skeleton, determines the antibacterial activity. Unfortunately, in opposition to what we expected, only one of the tested compounds inhibited the activity of the topoIV enzyme, and none of them was active against DNA gyrase.

1,4-Disubstituted thiosemicarbazide derivatives are potent inhibitors of Toxoplasma gondii proliferation

A series of 4-arylthiosemicarbazides substituted at the N1 position with a 5-membered heteroaryl ring was synthesized and evaluated in vitro for T. gondii inhibition proliferation and host cell cytotoxicity. At non-toxic concentrations for the host cells all studied compounds displayed excellent anti-parasitic effects when compared to sulfadiazine, indicating a high selectivity of their anti-T. gondii activity. The differences in bioactivity investigated by DFT calculations suggest that the inhibitory activity of 4-aryl-thiosemicarbazides towards T. gondii proliferation is connected with the electronic structure of the molecule. Further, these compounds were tested as potential antibacterial agents. No growth-inhibiting effect on any of the test microorganisms was observed for all the compounds, even at high concentrations.

Pharmacological and structure-activity relationship evaluation of 4-aryl-1-diphenylacetyl(thio)semicarbazides

This article describes the synthesis of six 4-aryl-(thio)semicarbazides (series a and b) linked with diphenylacetyl moiety along with their pharmacological evaluation on the central nervous system in mice and computational studies, including conformational analysis and electrostatic properties. All thiosemicarbazides (series b) were found to exhibit strong antinociceptive activity in the behavioural model. Among them, compound 1-diphenylacetyl-4-(4-methylphenyl)thiosemicarbazide 1b was found to be the most potent analgesic agent, whose activity is connected with the opioid system. For compounds from series a significant anti-serotonergic effect, especially for compound 1-diphenylacetyl-4-(4-methoxyphenyl)semicarbazide 2b was observed. The computational studies strongly support the obtained results.

Benzenesulfonamide bearing 1,2,4-triazole scaffolds as potent inhibitors of tumor associated carbonic anhydrase isoforms hCA IX and hCA XII

Three series of novel heterocyclic compounds (3a-3g, 4a-4g and 5a-5g) containing benzenesulfonamide moiety and incorporating a 1,2,4-triazole ring, have been synthesized and investigated as inhibitors against four isomers of the α-class carbonic anhydrases (CAs, EC 4.2.1.1), comprising hCAs I and II (cytosolic, ubiquitous isozymes) and hCAs IX and XII (transmembrane, tumor associated isozymes). Against the human isozymes hCA I and II, compounds of two series (3a-3g and 4a-4g) showed Ki values in the range of 84-868 nM and 5.6-390 nM, respectively whereas compounds of series 5a-5g were found to be poor inhibitors (Ki values exceeding 10,000 nM in some cases). Against hCA IX and XII, all the tested compounds exhibited excellent to moderate inhibitory potential with Ki values in the range of 2.8-431 nM and 1.3-63 nM, respectively. Compounds 3d, 3f and 4f exhibited excellent inhibitory potential against all of the four isozymes hCA I, II, IX and XII, even better than the standard drug acetazolamide (AZA) whereas compound of the series 5a-5g were comparatively less potent but more selective towards hCA IX and XII.

The antinociceptive effect of 4-substituted derivatives of 5-(4-chlorophenyl)-2-(morpholin-4-ylmethyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione in mice

The aim of the present experiments was to examine the antinociceptive activity of 4-substituted derivatives of 5-(4-chlorophenyl)-2-(morpholin-4-ylmethyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione in mice. The compounds were synthesized using the so-called Mannich reaction and their structures were confirmed using IR and 1H-NMR spectra. The antinociceptive activity was investigated in two behavioral tests: the hot plate test and the writhing test. For preliminary estimation of other behavioral effects, the locomotor activity of mice, the motor coordination in the rota-rod test, and the myorelaxation in the chimney test were also studied. The changes in body temperature of animals were also recorded. We demonstrated that all examined compounds produced antinociceptive effect, both in the hot plate test and in the writhing test, without impact on the motor coordination and myorelaxation of animals. The pharmacological effect of all drugs has been developed within 60 min after administration of drugs; and in two cases (T-103 and T-104), it has been a short-lasting effect (up to 90 min). Two compounds (T-100 and T-102) also inhibited the locomotor activity of animals. T-104 induced the changes in body temperature of mice. Generally, we demonstrated that combination of two different heterocyclic systems (morpholine and 1,2,4-triazole) might be beneficial for reduction of nociception.

Synthesis and antibacterial evaluation of some novel imidazole and benzimidazole sulfonamides

Several new substituted sulfonamide compounds were synthesized and their structures were confirmed by ¹H-NMR, ¹³C-NMR, FT-IR, and mass spectroscopy. The antibacterial activities of the synthesized compounds were screened against standard strains of six Gram positive and four Gram negative bacteria using the microbroth dilution assay. Most of the compounds studied showed promising activities against both types of bacteria.

Influence of 5-(3-chlorophenyl)-4-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione on the anticonvulsant action of 4 classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

BACKGROUND

The aim of this study was to determine the effects of 5-(3-chlorophenyl)-4-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP10) on the protective action of 4 classical antiepileptic drugs - carbamazepine, phenobarbital, phenytoin and valproate - against maximal electroshock-induced seizures in mice.

METHODS

Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by an electric current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2 s stimulus duration) delivered via auricular electrodes. Acute adverse-effect profiles with respect to motor performance, long-term memory and skeletal muscular strength were measured, together with total brain antiepileptic drug concentrations.

RESULTS

TP10 administered intraperitoneally at 10 mg/kg significantly elevated the threshold for electroconvulsions in mice. TP10 at doses of 2.5 and 5 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, TP10 (5 mg/kg) significantly enhanced the anticonvulsant activity of valproate, but not that of carbamazepine, phenobarbital or phenytoin in the maximal electroshock seizure test in mice. Pharmacokinetic experiments revealed that TP10 significantly elevated total brain concentrations of valproate in mice.

CONCLUSIONS

The enhanced anticonvulsant action of valproate by TP10 in the mouse maximal electroshock-induced seizure model was associated with a pharmacokinetic increase in total brain valproate concentrations in mice. The combinations of TP10 with carbamazepine, phenobarbital and phenytoin were neutral from a preclinical viewpoint.

Synthesis and evaluation of antimicrobial activity of hydrazones derived from 3-oxido-1H-imidazole-4-carbohydrazides

In this work we reported the synthesis and evaluation of in vitro antimicrobial activities of hydrazones 6 obtained from 3-oxido-1H-imidazole-4-carbohydrazides 4. All new compounds were characterized by spectroscopic methods. Hydrazones 6 were tested for their in vitro antimicrobial activity against four Gram-positive and four Gram-negative strains of bacteria as well as one fungal species. Three of the tested compounds appeared to be promising agents against reference strains of Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. They were also tested against twelve clinical isolates of S. aureus and their cytotoxic effect on murine fibroblasts and HeLa human tumor cell line was determined.

Synthesis, Characterization, and Biological Activity of Novel Schiff and Mannich Bases of 4-Amino-3-(N-phthalimidomethyl)-1,2,4-triazole-5-thione

The present work describes the syntheses and antimicrobial activity studies of a series of novel Schiff bases (4a–4i) and their Mannich bases (5a–5h) starting from 4-amino-3-(N-phthalimido-methyl)-1,2,4-triazole-5-thione (3). All the synthesized compounds were characterized by IR,1H-NMR,13C-NMR, and MS. All the synthesized compounds were screened for four Gram-negative strains, one Gram-positive strain of bacteria, and one diploid fungal strain. In general the antimicrobial activity increased remarkably on the introduction of azomethine functionality in parent triazole (3). The antimicrobial activity further improved when morpholine group was added to them except forEnterobacter cloacae, where loss of activity was observed. The results are promising and show that the fine tuning of the structures (5a, 5b, 5e, 5f,and5h) can lead to some new antimicrobial compounds.

Synthesis and in vitro activity of 1,2,4-triazole-ciprofloxacin hybrids against drug-susceptible and drug-resistant bacteria

A series of novel 1,2,4-triazole-ciprofloxacin hybrids was designed, synthesised and evaluated in vitro against drug-susceptible and drug-resistant bacteria. A significant part of the compounds obtained showed antibacterial activity higher than the activity of ciprofloxacin, both towards Gram-positive and Gram-negative species. Despite relatively small number of synthesised derivatives, it was possible to observe important dependences between their structure and activity.

Synthesis, characterization and preliminary anticonvulsant evaluation of some 4-alkyl-1,2,4-triazoles

Designed and synthesized 4-alkyl-1,2,4-triazole-3-thione derivatives showed significant anticonvulsant activity, determined in the maximal electroshock-induced seizure (MES) test. The chemical structure of all new compounds was confirmed by spectral methods ((1)H NMR, (13)C NMR, IR, MS). A sensitive and selective method was elaborated for the determination of the anticonvulsant compounds levels in mice brain tissue, based on HPLC with diode array detector (DAD). Chromatographic tests showed that lack of anticonvulsant effect of two derivatives (15, 16) with long alkyl chains at N-4 position of the 1,2,4-triazole ring was due to the inability to cross the blood-brain barrier (BBB).

Microbiologically active Mannich bases derived from 1,2,4-triazoles. The effect of C-5 substituent on antibacterial activity

Our research proved that chemical character of the C-5 substituent significantly determines the antibacterial activity of the Mannich bases derived from 4,5-disubstituted 1,2,4-triazole-3-thiones. This activity was considerably increased by an introduction of a chlorine atom to the phenyl ring. The obtained compounds were particularly active against opportunistic bacteria (Bacillus subtilis and Bacilluscereus). The antibacterial activity of some Mannich bases was similar or higher than the activity of commonly used antibiotics such as ampicillin and cefuroxime.

Effect of 4-(4-bromophenyl)-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione on the anticonvulsant action of different classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

The aim of this study was to determine the effects of 4-(4-bromophenyl)-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP4-a new S-triazole derivative possessing anticonvulsant properties in preclinical studies) on the protective action of four different classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) against maximal electroshock-induced seizures in mice. Results indicate that TP4 administered intraperitoneally at doses of 75 and 100 mg/kg significantly elevated the threshold for electroconvulsions in mice. TP4 at doses of 12.5, 25, 37.5 and 50 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, TP4 (50 mg/kg) significantly enhanced the anticonvulsant activity of carbamazepine, phenobarbital and valproate, but not that of phenytoin in the maximal electroshock seizure test in mice. TP4 at 25 mg/kg significantly potentiated the anticonvulsant action of carbamazepine, but not that of phenobarbital, phenytoin and valproate in the mouse maximal electroshock-induced seizure model. Pharmacokinetic experiments revealed that TP4 significantly elevated total brain concentrations of carbamazepine and valproate, having no impact on total brain concentrations of phenobarbital in mice. In conclusion, the enhanced anticonvulsant action of phenobarbital by TP4 was probably pharmacodynamic in nature and, therefore, the combination of TP4 with phenobarbital is worthy of consideration while extrapolating the results from this study into clinical settings. The enhanced anticonvulsant action of carbamazepine and valproate by TP4 in the mouse maximal electroshock-induced seizure model was associated with pharmacokinetic increases in total brain concentrations of the antiepileptic drugs in mice. The combination of TP4 with phenytoin was neutral from a preclinical point of view.

Synthesis and antibacterial evaluation of New N-acylhydrazone derivatives from dehydroabietic acid

A series of new N-acylhydrazone derivatives were synthesized in good yields through the reactions of dehydroabietic acid hydrazide with a variety of substituted arylaldehydes. The structures of the synthesized compounds were confirmed by IR, 1H- and 13C-NMR, ESI-MS, elemental analysis and single crystal X-ray diffraction. From the crystal structure of compound 4l, the C=N double bonds of these N-acylhydrazones showed (E)-configuration, while the NMR data of compounds 4a-q indicated the existence of two rotamers for each compound in solution. The target compounds were evaluated for their antibacterial activities against four microbial strains. The result suggested that several compounds exhibited pronounced antibacterial activities. Particularly, compound 4p exhibited good antibacterial activity against Staphylococcus aureus and Bacillus subtilis comparable to positive control. The possible antibacterial metabolism and the strategy for further optimization of this compound were also discussed.

New heterocyclic compounds from 1,2,4-triazole and 1,3,4-thiadiazole class bearing diphenylsulfone moieties. Synthesis, characterization and antimicrobial activity evaluation

Some new 5-(4-(4-X-phenylsulfonyl)phenyl)-4-(R)-2H-1,2,4-triazol-3(4H)-thiones 4a,b; 5a,b and 5-(4-(4-X-phenylsulfonyl)phenyl)-N-(R)-1,3,4-thiadiazol-2-amines 6a,b; 7a,b were obtained by cyclization of new N(1)-[4-(4-X-phenylsulfonyl)benzoyl]-N(4)-(R)-thiosemicarbazides 2a,b; 3a,b (X=H, Br). The 1,2,4-triazoles were synthesized by intramolecular cyclization of acylthiosemicarbazides, in basic media. On the other hand, 1,3,4-thiadiazoles were obtained from same acylthiosemicarbazides, in acidic media. These new intermediates from thiosemicarbazide class were afforded by the reaction of 4-(4-X-phenylsulfonyl)benzoic acids hydrazides (X=H, Br) 1a,b with 4-trifluoromethoxyphenyl or 3,4,5-trimethoxyphenyl isothiocyanate. The newly synthesized compounds were characterized by IR, (1)H NMR, (13)C NMR, MS and elemental analysis. All the new compounds were screened for their antimicrobial activity against some bacteria (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 13061, Escherichia coli ATCC 25922, Enterobacter cloacae ATCC 49141, Acinetobacter baumannii ATCC 19606 and Pseudomonas aeruginosa ATCC 27853) and yeasts (Candida albicans ATCC 90028 and Candida parapsilosis ATCC 22019).

Studies on the synthesis and antibacterial activity of 3,6-disubstituted 1,2,4-triazolo[3,4-b]1,3,4-thiadiazoles

Treating infections caused by drug-resistant bacterial strains constitutes one of the most essential challenges for medicine nowadays. A range of new derivatives of 1,2,4-triazolo[3,4-b]1,3,4-thiadiazole have been synthesized and evaluated for their in vitro antimicrobial activity. Compounds 1-8 indicated high activity towards Gram-positive bacteria, which was up to 16 times more than currently used antibiotics. To the best of our knowledge, the derivatives obtained by us are the most active among the 3-aryl-6-arylamino-1,2,4-triazolo[3,4-b]1,3,4-thiadiazoles known until now.