Synthesis, characterization and physiochemical information, along with antimicrobial studies of some metal complexes derived from an ON donor semicarbazone ligand

Eight new transition metal complexes of benzaldehyde-N(4)-phenylsemicarbazone have been synthesized and characterized by elemental analyses, molar conductance, electronic and infrared spectral studies. In all the complexes, the semicarbazone is coordinated as neutral bidentate ligand. (1)H NMR spectrum of [Zn(HL)(2)(OAc)(2)] shows that there is no enolisation of the ligand in the complex. The magnetic susceptibility measurements indicate that Cr(III), Mn(II), Fe(III), Co(II) and Cu(II) complexes are paramagnetic and Ni(II) is diamagnetic. The EPR spectrum of [Mn(HL)(2)(OAc)(2)] in DMF solution at 77K shows hyperfine sextet with low intensity forbidden lines lying between each of the two main hyperfine lines. The g values calculated for the [Cu(HL)(2)SO(4)] complex in frozen DMF, indicate the presence of unpaired electron in the d(x)(2) - (y)(2) orbital. The metal ligand bonding parameters evaluated showed strong in-plane sigma bonding and in-plane pi bonding. The ligand and complexes were screened for their possible antimicrobial activities.

Field and laboratory trials of a novel metaflumizone house fly (Diptera: Muscidae) bait in California

House fly responses to metaflumizone bait were studied in southern California. Field-strain, laboratory-reared flies in outdoor cages had access for 5 d to water and two containers of untreated sugar/dry milk (control), one container of untreated food and one container of metaflumizone bait, or one container of untreated food and one container of spinosad bait (positive control). Most fly mortality occurred between 0 and 48 h for spinosad and between 48 and 96 h for metaflumizone. On a commercial dairy, fly visitation and bait consumption were higher for metaflumizone bait than for sugar or imidacloprid bait. Flies seldom visited or consumed the imidacloprid bait. Approximately 32% of field flies collected directly from metaflumizone bait (single exposure) died when held in the laboratory with untreated food for 72 h versus < 5% mortality for flies from sugar or imidacloprid bait. Individual laboratory-reared females from a field strain and a susceptible laboratory strain were videotaped in the laboratory after exposure to untreated dry milk/sugar, metaflumizone bait, spinosad bait, and imidacloprid bait. Imidacloprid-induced mortality in field strain flies was low; when on the bait they spent proportionally less time feeding (38%) than did the laboratory strain flies (63%). Feeding by the field strain was more variable, and they fed less on all bait/food sources except metaflumizone. Metaflumizone has promise as a relatively slow-acting fly bait.

Microwave assisted synthesis, characterization and biological evaluation of palladium and platinum complexes with azomethines

Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicarbazone (C(9)H(13)N(3)OS(2) or L(1)H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C(9)H(13)N(3)OS or L(2)H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, (1)H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the complexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested.

Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: synthesis, structural characterization and biological studies

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO(2)(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV-vis, ESR, (1)H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H(4)L(1)) and the semicarbazone (H(4)L(2)) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO(2)(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H(3)L(3)) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H(4)L(1) ligand showed a higher antibacterial effect than the free ligand while the other ligands (H(4)L(2) and H(3)L(3)) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.

Evaluation of metaflumizone granular fly bait for management of houseflies

The housefly, Musca domestica L. (Diptera: Muscidae), is a pest of great veterinary and public health importance. In this study, the efficacy of metaflumizone granular fly bait was assessed on first generation (F1) housefly adults raised from flies collected at a cattle feedlot in Kansas. All bioassays were conducted as choice tests, with flies having ad libitum access to water, granular sugar and bait. A commercial methomyl-based bait (Golden Malrin) was used as positive control; no bait (water and granular sugar only) was used as negative control. Fly mortality was recorded on days 2, 7 and 14. The metaflumizone bait was significantly more slow-acting than the methomyl bait (mortality rates after 2 days of exposure were 49.9% and 57.9%, respectively). However, there were no significant differences in cumulative mortality later in the bioassays. Cumulative mortality rates on days 7 and 14 were 96.1% (metaflumizone), 91.4% (methomyl) and 99.0% (metaflumizone), 97.6% (methomyl), respectively. Our results demonstrate that the metaflumizone granular fly bait may be an effective modality for incorporation into management programmes for houseflies in and around livestock production facilities as well as in residential settings.

Synthesis of some new coumarin incorporated thiazolyl semicarbazones as anticonvulsants

Several heteroaryl semicarbazones were prepared by the reaction of heteroaryl hydrazine carboxamide with aryl aldehydes or ketones. The structures of the synthesized compounds were confirmed by spectral data and elemental analyses. Compounds were tested for anticonvulsant activity utilizing pentylenetetrazole-induced seizure (PTZ) and maximal electroshock seizure (MES) tests at 30, 100 and 300 mg/kg dose levels. Neurotoxicity of the compounds was also assessed at the same dose levels. Three compounds of the series, 6d, 6i and 6n, exhibited significant anticonvulsant activity at 30 mg/kg dose level comparable to the standard drug, phenytoin.

Synthesis, Analgesic and Anti-Inflammatory Activity of 4-(2-Phenoxyphenyl)semicarbazones

A series of 4-(2-phenoxyphenyl)semicarbazones was synthesized and evaluated for their analgesic and anti-inflammatory activities. Several compounds (e. g. 10h, 10i, and 11i) were found to be more potent than the reference drug mefenamic acid in the formalin test. Based on the results of an anti-inflammatory study, 1-(1-(2,5-dimethoxyphenyl)ethylidene)-4-(2-phenoxyphenyl)semicarbazide 11i was the most active compound.

Discovery of 4-aminobutyric acid derivatives possessing anticonvulsant and antinociceptive activities: a hybrid pharmacophore approach

Antiepileptic drugs are often utilized in the treatment of neuropathic pain. The present study aims at the design and synthesis of newer gamma-aminobutyric acid (GABA) derivatives with the combination of aryl semicarbazone and the GABA pharmacophores in order to develop a multifunctional drug useful in the treatment of neurological disorders like epilepsy and neuropathic pain. Various GABA semicarbazones were synthesized and screened for anticonvulsant, peripheral analgesic, antiallodynic, and antihyperalgesic activities. The structures of the synthesized compounds were confirmed by the use of their spectral data in addition to elemental analysis. The synthesized derivatives of the inhibitory neurotransmitter GABA produced anticonvulsant and antinociceptive actions in the acetic acid induced writhing test and peripheral nerve injury (chronic constriction injury and L5 spinal nerve ligation) models of neuropathic pain. The underlying mechanisms are expected to be enhancement of peripheral GABAergic neurotransmission owing to their activity in the scPIC screen and due to various reports on the involvement of GABAergic pathway in peripheral models of neuropathic pain.

Microwave-assisted synthesis, anticonvulsant activity and quantum mechanical modelling of N-(4-bromo-3-methylphenyl) semicarbazones

OBJECTIVE

To study the effect of halo substitution on disubstituted aryl semicarbazones on the anticonvulsant potential and model the activity based on quantum mechanics.

METHODS

A series of twenty-six compounds of N(4)-(4-bromo-3-methylphenyl) semicarbazones were synthesized and evaluated for the anticonvulsant activity in the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure threshold tests. Some potential compounds were also tested in the subcutaneous strychnine (scSTY) and subcutaneous picrotoxin (scPIC) seizure threshold tests. The synthesized compounds were tested for behavioral impairment and CNS (central nervous system) depression in mice. Quantum mechanical modelling was carried out on these compounds to gain understanding on the structural features essential for activity.

RESULTS

Some compounds possessed broad spectrum anticonvulsant activity as indicated by their effect in pentylenetetrazole, strychnine, picrotoxin and maximal electroshock seizures models in resemblance to other aryl semicarbazone derivatives reported earlier. The higher the difference in HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels was, the greater was the activity profile.

CONCLUSION

The pharmacophoric requirements for compounds to exhibit anticonvulsant activity that includes one aryl unit in proximity to a hydrogen donor-acceptor domain and an electron donor have been justified with the molecular orbital surface analysis of the synthesized compounds.

Nitrofurylsemicarbazone Rhenium and Ruthenium Complexes as Anti-trypanosomal Agents

Rhenium and ruthenium complexes of the type [Re(V)OCl(2)(PPh(3))L] and [Ru(II)Cl(2)(DMSO)(2)L], where L are 5-nitrofurylsemicarbazone derivatives, were prepared in an effort to obtain new anti-trypanosomal agents combining the recognized biological activity of these metals and the trypanocidal activity of the free ligands. Rhenium complexes resulted unstable in aqueous solution not allowing their use as potential drugs. On the other hand, complexation to ruthenium of the bioactive ligands lead to the lack of antiprotozoa activity even though free radical production and redox cycling induction were detected when the compounds were incubated in presence of Trypanosoma cruzi cells. The lack of anti-trypanosomal activity of ruthenium complexes could be explained on the basis of their high protein binding capacity and their high hydrophilicity.

Discovery and synthesis of tetrahydroindolone derived semicarbazones as selective Kv1.5 blockers

A novel class of tetrahydroindolone-derived semicarbazones has been discovered as potent Kv1.5 blockers. In in vitro studies, several compounds exhibited very good potency for blockade of Kv1.5. Compound 8i showed good selectivity for blockade of Kv1.5 vs hERG and L-type calcium channels. In an anesthetized pig model, compounds 8i and 10c increased atrial ERP about 28%, 18%, respectively, in the right atrium without affecting ventricular ERP.

Quantum Mechanical Modeling of N4-(2, 5-Disubstituted phenyl) Semicarbazones: Synthesis and Anticonvulsant Activity of N4-(2, 5-dimethylphenyl/ -2-fluoro-5-methyl phenyl) Semicarbazones

Two new series of N4-(2, 5-disubstitutedphenyl) semicarbazones were synthesized and evaluated for the anticonvulsant activity in various animal models of seizures. Quantum mechanical modeling was carried out on these compounds to understand the structural features essential for activity. The higher the difference in HOMO and LUMO energy levels the greater was the activity profile. Substitution with fluoro group on the ortho position of the aryl ring was found to decrease the reactivity and hence the activity profile of aryl semicarbazones, which has been justified with the molecular orbital surface analysis of the synthesized compounds.

Synthesis of N4-(2,4-dimethylphenyl) semicarbazones as 4-aminobutyrate aminotransferase inhibitors

Several 2,4-dimethylphenyl substituted semicarbazones were synthesized in three steps involving aryl urea and aryl semicarbazide formation. The structures were confirmed by spectral and elemental analyses. All the compounds were evaluated for anticonvulsant activity by using a series of test models, including maximal electroshock seizure, subcutaneous pentylenetetrazole and subcutaneous strychnine seizure threshold tests. The compounds were also evaluated for behavioural impairement and depression activity. In the neurochemical investigation, potent compounds were evaluated for their effects on rat brain gamma-aminobutyric acid (GABA) levels and in vitro gamma-aminobutyrate transaminase (Pseudomonas fluorescens) activity. Preliminary studies suggest that these compounds exhibit anticonvulsant activity via a GABA-mediated mechanism.

Syntheses, crystal structures and antimicrobial activities of 6-coordinate antimony(III) complexes with tridentate 2-acetylpyridine thiosemicarbazone, bis(thiosemicarbazone) and semicarbazone ligands

Five novel antimony(III) complexes with the mono- and bis(thiosemicarbazone) ligands of 2N1S or 4N2S donor atoms, N'-[1-(2-pyridyl)ethylidene]morpholine-4-carbothiohydrazide (Hmtsc, L1) and bis[N'-[1-(2-pyridyl)ethylidene]]-1,4-piperazinedicarbothiohydrazide (H(2)ptsc, L7), and the tridentate semicarbazone ligand of 2N1O donor atoms, 2-acetylpyridine semicarbazone (Hasc, L2b), were prepared by reactions of SbCl(3) or SbBr(3), and characterized by elemental analysis, TG/DTA, FT-IR and (1)H NMR spectroscopy. The crystal and molecular structures of five antimony(III) complexes were determined by single-crystal X-ray structure analysis. The neutral, 6-coordinate antimony(III) complexes ([Sb(mtsc)Cl(2)] 1, [Sb(mtsc)Br(2)] 2, [Sb(asc)Cl(2)] 3 and [Sb(asc)Br(2)] 4) are depicted with one electron pair (5s(2)) of the antimony(III) atom, deprotonated forms of multidentate thiosemicarbazone or semicarbazone ligands, and two monodentate halogen ligands, respectively. In the dimer complex 5 ([Sb(2)(ptsc)Cl(4)]) with the ligand in which two tridentate thiosemicarbazone moieties are connected by the piperazine moiety, each antimony(III) was also described as a neutral 6-coordinate structure. These antimony(III) complexes were thermally stable around 200 degrees C. Water-soluble antimony(III) complexes 1 and 2 showed moderate antimicrobial activities against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and -negative bacteria (Escherichia coli and Pseudomonas aeruginosa), yeasts (Candida albicans and Saccharomyces cerevisiae) and molds (Aspergillus niger and Penicillium citrinum). Complex 5 showed moderate antimicrobial activities against four bacteria, and two molds, while the ligand itself showed only modest antimicrobial activities against selected bacteria (B. subtilis, E. coli and S. aureus). The molecular structures and antimicrobial activities of antimony(III) complexes were compared with those of bismuth(III) complexes in the same 15 group in the periodic table.

Antinociceptive, antiedematogenic and antiangiogenic effects of benzaldehyde semicarbazone

Semicarbazones induce an anticonvulsant effect in different experimental models. As some anticonvulsant drugs also have anti-inflammatory activity, the effects of benzaldehyde semicarbazone (BS) on models of nociception, edema and angiogenesis were investigated. BS (10, 25 or 50 mg/kg, i.p.) markedly inhibited the second phase of nociceptive response induced by formaldehyde (0.34%, 20 microl) in mice, but only the highest dose inhibited the first phase of this response. The thermal hyperalgesia and mechanical allodynia induced by carrageenan (1%, 50 microl, i.pl.) in rats were also inhibited by BS (50 mg/kg, i.p.). However, treatment of mice with BS did not induce an antinociceptive effect in the hot-plate model. The paw edema induced by carrageenan (1%, 50 microl, i.pl.) in rats was inhibited by BS (25 or 50 mg/kg, i.p.). Treatment of mice with BS (0.25, 0.5 or 2.5 mg/kg/day, i.p., 7 days) also inhibited angiogenesis induced by subcutaneous implantation of a sponge disc. It is unlikely that the antinociceptive effect induced by BS results from motor incoordination or a muscle relaxing effect, as the mice treated with this drug displayed no behavioral impairment in the rotarod apparatus. In conclusion, we demonstrated that BS presents antinociceptive, antiedematogenic and antiangiogenic activities. An extensive investigation of the pharmacological actions of BS and its derivatives is justified and may lead to the development of new clinically useful drugs.

Pharmacology of 2-[4-(4-Chloro-2-fluorophenoxy)phenyl]-pyrimidine-4-carboxamide: A Potent, Broad-Spectrum State-Dependent Sodium Channel Blocker for Treating Pain States

Voltage-gated Na(+) channels may play important roles in establishing pathological neuronal hyperexcitability associated with chronic pain in humans. Na(+) channel blockers, such as carbamazepine (CBZ) and lamotrigine (LTG), are efficacious in treating neuropathic pain; however, their therapeutic utility is compromised by central nervous system side effects. We reasoned that it may be possible to gain superior control over pain states and, in particular, a better therapeutic index, by designing broad-spectrum Na(+) channel blockers with higher potency, faster onset kinetics, and greater levels of state dependence than existing drugs. 2-[4-(4-Chloro-2-fluorophenoxy)phenyl]-pyrimidine-4-carboxamide (PPPA) is a novel structural analog of the state-dependent Na(+) channel blocker V102862 [4-(4-fluorophenoxy)benzaldehyde semicarbazone]. Tested on recombinant rat Na(v)1.2 channels and native Na(+) currents in cultured rat dorsal root ganglion neurons, PPPA was approximately 1000 times more potent, had 2000-fold faster binding kinetics, and > or =10-fold higher levels of state dependence than CBZ and LTG. Tested in rat pain models against mechanical endpoints, PPPA had minimal effective doses of 1 to 3 mg/kg p.o. in partial sciatic nerve ligation, Freund's complete adjuvant, and postincisional pain. In all cases, efficacy was similar to clinically relevant comparators. Importantly, PPPA did not produce motor deficits in the accelerating Rotarod assay of ataxia at doses up to 30 mg/kg p.o., indicating a therapeutic index >10, which was superior to CBZ and LTG. Our experiments suggest that high-potency, broad-spectrum, state-dependent Na(+) channel blockers will have clinical utility for treating neuropathic, inflammatory, and postsurgical pain. Optimizing the biophysical parameters of broad-spectrum voltage-gated Na(+) channel blockers may lead to improved pain therapeutics.

Semicarbazone-based inhibitors of cathepsin K, are they prodrugs for aldehyde inhibitors?

Starting from potent aldehyde inhibitors with poor drug properties, derivatization to semicarbazones led to the identification of a series of semicarbazone-based cathepsin K inhibitors with greater solubility and better pharmacokinetic profiles than their parent aldehydes. Furthermore, a representative semicarbazone inhibitor attenuated bone resorption in an ex vivo rat calvarial bone resorption model. However, based on enzyme inhibition comparisons at neutral pH, semicarbazone hydrolysis rates, and 13C NMR experiments, these semicarbazones probably function as prodrugs of aldehydes.

2,4-Dimethoxyphenylsemicarbazones with anticonvulsant activity against three animal models of seizures: synthesis and pharmacological evaluation

Various 2,4-dimethoxyphenylsemicarbazones were synthesized starting from 2,4-dimethoxyaniline via a phenylcarbamate intermediate. The structures were confirmed by spectral and elemental analyses. The anticonvulsant activity of the synthesized compounds was established after intraperitoneal administration in three seizure models in mice which include maximal electroshock seizure, subcutaneous pentylenetetrazole, and subcutaneous strychnine-induced seizure screens. Nine compounds exhibited protection in all the three seizure models, and N1-(2,4-dimethoxyphenyl)-N4-(propan-2-one)semicarbazone (17) emerged as the most active compound with no neurotoxicity. These compounds were found to elevate gamma-aminobutyric acid (GABA) levels in the midbrain and medulla oblongata regions equipotent to clobazam.

Discovery of N-(2,6-Dimethylphenyl)-Substituted Semicarbazones as Anticonvulsants: Hybrid Pharmacophore-Based Design

Epilepsy is the most common primary neurological disorder known. In the past decade, various aryl semicarbazones have been designed that were structurally dissimilar from many common anticonvulsants containing the dicarboximide function (CONRCO), which may contribute to toxic side effects. In the present work various N4-(2,6-dimethylphenyl) semicarbazones were designed as pharmacophore hybrids between the aryl semicarbazones and ameltolide. A three-dimensional four-point pharmacophore model was developed for anticonvulsants, and the title compounds were found to match with ralitoline. All of the compounds exhibited anticonvulsant activity in the maximal electroshock test when administered by both intraperitoneal and oral routes. Compound N1-(2,6-dimethylphenyl)-N4-(2-hydroxybenzaldehyde) semicarbazone (9) emerged as a prototype with wide spectrum anticonvulsant agent active in five models of seizure with no neurotoxicity and hepatotoxicity. Compound 9 increased the 4-aminobutyric acid (GABA) level by 118% and inhibited the GABA transaminase enzyme both in vitro and ex vivo.

V102862 (Co 102862): a potent, broad-spectrum state-dependent blocker of mammalian voltage-gated sodium channels

1. 4-(4-Fluorophenoxy)benzaldehyde semicarbazone (V102862) was initially described as an orally active anticonvulsant with robust activity in a variety of rodent models of epilepsy. The mechanism of action was not known. We used whole-cell patch-clamp techniques to study the effects of V102862 on native and recombinant mammalian voltage-gated Na+ channels. 2. V102862 blocked Na+ currents (I(Na)) in acutely dissociated cultured rat hippocampal neurons. Potency increased with membrane depolarization, suggesting a state-dependent mechanism of inhibition. There was no significant effect on the voltage dependence of activation of I(Na). 3. The dissociation constant for the inactivated state (K(I)) was approximately 0.6 microM, whereas the dissociation constant for the resting state (K(R)) was >15 microM. 4. The binding to inactivated channels was slow, requiring a few seconds to reach steady state at -80 mV. 5. The mechanism of inhibition was characterized in more detail using human embryonic kidney-293 cells stably expressing rat brain type IIA Na+ (rNa(v)1.2) channels, a major Na+ channel alpha subunit in rat hippocampal neurons. Similar to hippocampal neurons, V102862 was a potent state-dependent blocker of rNa(v)1.2 channels with a K(I) of approximately 0.4 microM and K(R) approximately 30 microM. V102862 binding to inactivated channels was relatively slow (k(+) approximately = 1.7 microM(-1) s(-1)). V102862 shifted the steady-state availability curve in the hyperpolarizing direction and significantly retarded recovery of Na+ channels from inactivation. 6. These results suggest that inhibition of voltage-gated Na+ channels is a major mechanism underlying the anticonvulsant properties of V102862. Moreover, understanding the biophysics of the interaction may prove to be useful in designing a new generation of potent Na+ channel blocker therapeutics.

Antioxidant and antiproliferative activity of curcumin semicarbazone

A new semicarbazone derivative of curcumin (CRSC) was synthesized and examined for its antioxidant, antiproliferative, and antiradical activity and compared with those of curcumin (CR). The antioxidant activity was tested by their ability to inhibit radiation induced lipid peroxidation in rat liver microsomes. The antiproliferative activity was tested by studying the in vitro activity of CRSC against estrogen dependant breast cancer cell line MCF-7. Kinetics of reaction of (2,2'-diphenyl-1-picrylhydrazide) DPPH, a stable hydrogen abstracting free radical was studied to measure the antiradical activity using stopped-flow spectrophotometer. Finally one-electron oxidized radicals of CRSC were generated and characterized by pulse radiolysis. The results suggest that the probable site of attack for CRSC is both the phenolic OH and the imine carbonyl position. CRSC shows efficient antioxidant and antiproliferative activity although its antiradical activity is less than that of CR.

Anticonvulsants containing the N-(3-aryl-2-propenoyl) amido pharmacophore

A series of 1-(3-aryl-2-propenoyl)-4-oxopiperidines (1) as well as some related semicarbazones (2) and thiosemicarbazones (3) were prepared in order to determine whether the relative locations of aryl rings and amidic groups would lead to novel anticonvulsant agents. Initially the compounds were administered intraperitoneally to mice and examined in the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) and neurotoxicity (NT) screens. The biodata revealed that anticonvulsant properties were displayed by most of the compounds in series (1), in half of the semicarbazones (2) while protection was absent by members of series (3). Molecular modeling was utilized in order to compare the positions of a phenyl ring in relation to amidic groups in representative compounds in series (1-3) with previously reported anticonvulsant agents. Molecular simplification of 4-oxo-1-(3-phenyl-2-propenoyl)piperidine (la) led to 1-(3-phenyl-2-propenoyl)piperidine (7) and N,N-diethylcinnamamide (8) with retention of anticonvulsant properties. Both (la) and (8) afforded protection in the hippocampal kindling screen in rats. When administered orally to rats, (la) and (8) demonstrated activity in the MES screen and in the case of (8), a huge protection index was observed revealing it to be an important lead compound. The IC50 values of all of the compounds towards murine P388 cells were in excess of 50 microM while several compounds displayed cytotoxicity towards Mycobacterium tuberculosis.

Synthesis of aryl semicarbazones as potential anticonvulsant agents

A series of 4-ethoxyphenyl semicarbazones (1-10) have been synthesized using an appropriate synthetic route and characterized by elemental analyses and spectral data. The anticonvulsant activity of all the synthesized compounds was evaluated against maximal electroshock induced seizures (MES) and subcutaneous pentylenetetrazole (scPTZ) induced seizure models in mice. The neurotoxicity was assessed using the rotorod method. All the test compounds were administered at doses of 30, 100, and 300 mg/kg body weight and the anticonvulsant activity was noted at 0.5 and 4 h time intervals after the drug administration. Among the compounds tested, compounds except 3, 4 and 10 showed protection from seizures in both the animal models. Compounds 6 and 8 were found to increase gamma-aminobutyric acid (GABA) levels in the medulla oblongata region of the rat brain.

The wide pharmacological versatility of semicarbazones, thiosemicarba-zones and their metal complexes

The more significant bioactivities of a variety of semicarbazones (anti-protozoa, anticonvulsant) and thiosemicarbazones (antibacterial, antifungal, antitumoral, antiviral) and their metal complexes are reviewed together with proposed mechanisms of action and structure-activity relationships. Clinical or potential pharmacological applications of these versatile compounds are discussed.