Schiff base transition metal complexes as novel inhibitors of xanthine oxidase

Twenty transition metal complexes with Schiff bases were evaluated for their inhibitory activities on xanthine oxidase (XO), of which 11 were newly synthesized and characterized by X-ray single crystal diffraction. It was found that 9 of the 20 complexes showed potent inhibitory activities against XO near to the standard inhibitor allopurinol. The cadmium(II) complex (8) had the most potent inhibitory activity with the IC(50) value of 2.16 microM. Relationships between the structures and the activities showed that the ligands and the metal ions influenced the inhibitory activities. The XO inhibition of the Schiff base metal complexes most probably resulted from their direct interactions with the enzymes "in the whole complex form". These results demonstrated that the Schiff base transition metal complexes could be potential selective XO inhibitors.     

New transition metal ion complexes with benzimidazole-5-carboxylic acid hydrazides with antitumor activity

Metal complexes of 2-methyl-1H-benzimidazole-5-carboxylic acid hydrazide (4a; L(1)) and its Schiff base 2-methyl-N-(propan-2-ylidene)-1H-benzimidazole-5-carbohydrazide (5a; L(2)) with transition metal ions e.g., copper, silver, nickel, iron and manganese were prepared. The complexes formed were 1:1 or 1:2 M:L complexes and have the structural formulae [Cu(L(1))Cl(H(2)O)]Cl x 3 H(2)O (6), [Ag(L(1))NO(3)(H(2)O)] (7), [Ni(L(1))Cl(2)(H(2)O)(2)] x H(2)O (8), [Fe(L(1))Cl(3)(H(2)O)] x 3 H(2)O (9) and [Mn(L(1))(2)Cl(H(2)O)]Cl x 3 H(2)O (10) for ligand L(1), and [Cu(L(2))Cl(2)(H(2)O)(2)] x H(2)O (11), [Ag(L(2))(2)]NO(3) x H(2)O (12), [Ni(L(2))(2)Cl(2)] x 5 H(2)O (13), [Fe(L(2))(2)Cl(2)]Cl x 2 H(2)O (14) and [Mn(L(2))Cl(2)(H(2)O)(2)] x H(2)O (15) for ligand L(2). The antitumor activity of the synthesized compounds has been studied. The silver complex 7 was found to display cytotoxicity (IC(50)=2 microM) against both human lung cancer cell line A549 and human breast cancer cell line MCF-7.     

Studies on novel 4beta-[(4-substituted)-1,2,3-triazol-1-yl] podophyllotoxins as potential anticancer agents

A series of 4beta-[(4-substituted)-1,2,3-triazol-1-yl] podophyllotoxin congeners have been designed and synthesized with significant regioselectivity by employing Cu(I) catalyzed 1,3-dipolar cycloaddition reaction of C4beta-azido podophyllotoxin and C4beta-azido-4'-O-demethyl podophyllotoxin with N-prop-2-yn-1-ylanilines. These compounds were evaluated for anticancer activity against a panel of seven human cancer cell lines. It was interesting to note that all the compounds exhibited promising activity especially against SF-295 (CNS), HCT-15 (colon) and 502713 (colon) cell lines. Compound 11e was found to be the most promising in this study.     

Spectroscopy of the spin sublevels of transition metal complexes

The theoretical and experimental aspects of the spin sublevels of transition metal complexes are briefly reviewed. First, the complexes with organic ligands are discussed. For metal-localizeddd states and metal-to-ligand charge transferdπ* states, the splitting among spin sub-levels is mainly governed by the spin-orbit coupling, and the magnitude of the splitting is of the order of 10–100 cm⁻¹. For ligand-localized tripletππ* states, the splitting is mainly governed by the spin-spin coupling, and the magnitude of the splitting is mainly governed by the spin-spin coupling and the magnitude of the splitting is of the order of 0.1 cm⁻¹. Theoretical evaluation of the radiative rate constants for the individual spin sublevels is discussed, and is compared with experimental data. Finally, the spin sublevels of metal clusters are discussed.     

Synthesis of new 4-pyrrol-1-yl benzoic acid hydrazide analogs and some derived oxadiazole, triazole and pyrrole ring systems: a novel class of potential antibacterial and antitubercular agents

In the present study, a novel series of 4-pyrrol-1-yl benzoic acid hydrazide analogs, some derived 5-substituted-2-thiol-1,3,4-oxadiazoles, 5-substituted-4-amino-1,2,4-triazolin-3-thione and 2,5-dimethyl pyrroles have been synthesized in good yields and characterized by IR, NMR, mass spectral and elemental analyses. Compounds were evaluated for their preliminary in vitro antibacterial activity against some Gram-positive and Gram-negative bacteria and compounds were screened for antitubercular activity against Mycobacterium tuberculosis H37Rv strain by broth dilution assay method. Some compounds showed very good antibacterial and antitubercular activities.     

Synthesis, characterization, antifungal and anti-HIV activities of metal(II) complexes of 4,6-di-tert-butyl-3-[(2-hydroxyethyl)thio]benzene-1,2-diol

Co(II) and Ni(II) complexes with 4,6-di-tert-butyl-3-[(2-hydroxyethyl)thio]benzene-1,2-diol (L) have been synthesized and characterized by means of elemental analysis, TG/DTA, FT-IR, ESR, UV-vis, XRD, magnetic susceptibility, cyclic voltammetry and conductance measurements. According to the data obtained the organic compound acts as a bidentate O,S-coordinated ligand and yields Co(II) and Ni(II) complexes of the stoichiometry ML(2) which is characterized by square planar geometry. Antifungal and anti-HIV activities of the ligand and its metal(II) complexes were found to decrease in the sequence CuL(2)>CoL(2) ~ NiL(2)>HL, along with their reducing ability (determined electrochemically).     

Synthesis and crystal structure of some transition metal complexes with a novel bis-Schiff base ligand and their antitumor activities

Mononuclear complex of Zn(II) with a new bis-Schiff base ligand derived from 2,3-butanedione and thiosemicarbazide, [Zn(II)L.H2O].2DMF [L = (2E,2'E)-2,2'-(butane-2,3-diylidene)bis(hydrazinecarbothioamide)], and other transition metal ions [Cu(II), Mn(II), Co(II), Ni(II)] complexes have been prepared. The Zn(II) complex has been structurally characterized by X-ray crystallography. Among the five complexes, the Cu(II) complex has the novel highest antitumor activity.     

Design & synthesis of N'-[substituted] pyridine-4-carbohydrazides as potential anticonvulsant agents

A series of N′-[substituted] pyridine-4-carbohydrazides were designed and synthesized keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant activity and neurotoxicity. The anticonvulsant activity of the titled compounds was established after intraperitoneal administration in three seizure models, which include MES, scMET and 6 Hz model. The most active compound of the series was N′-[4-(4-fluorophenoxy)benzylidene]pyridine-4-carbohydrazide PCH 6, which showed a MES ED₅₀ value of 128.3 mg/kg and 6 Hz ED₅₀ value of 53.3 mg/kg in mice. The median toxic dose (TD₅₀) was 343.6 mg/kg, providing compound PCH 6 with a protection index of 2.67 in the MES test and 6.44 in 6 Hz test. A computational study was also carried out, including calculation of pharmacophore pattern, prediction of pharmacokinetic properties and docking studies.     

On the formation of steroidal amidoesters of 4-[N,N-bis(2-chloroethyl)amino]benzoic acid and their cytotoxic activity

The 4-[N,N-bis(2-chloroethyl)amino]benzoate of 17beta-acetamido-5alpha-androstan-3beta-ol, 17beta-acetamido-5-androsten-3beta-ol, 3beta-acetamido-5alpha-androstan-17beta-ol and 3alpha-acetamido-5beta-androstan-17beta-ol have been prepared and their antineoplastic effect evaluated against MIA Pa-Ca-2 pancreatic carcinoma, T47D breast carcinoma and A431 squamus cell carcinoma. Among the compounds tested, the compound 17beta-acetamido-3beta-hydroxy-5-androsten-4-[N, N-bis(2-chloroethyl)amino]benzoate appeared to possess a significant cytotoxic effect against A431 cells.     

A quantitative structure-activity relationship study on a novel class of calcium-entry blockers: 1-[(4-(aminoalkoxy)phenyl)sulphonyl]indolizines

A quantitative structure-activity relationship (QSAR) study has been made on two different series of 1-[(4-(aminoalkoxy)phenyl)sulphonyl]indolizines acting as calcium entry blockers, using some physicochemical and structural parameters. Two different assays were reported for both the series: (IC(50))(A), referring to the molar concentration of the compound required to reduce [3H] nitrendipine binding by 50%, and (IC(50))(B), referring to that required to block Ca(2+) induced concentration of K(+) depolarised rat aorta by 50%. For series 1, where the 2-position substituents of indolizine ring were varied along with the aminoalkoxy moieties of the phenyl ring, the QSAR analysis shows that the 2-position substituents can equally affect both the activities through their hydrophobic and electronic properties and the aminoalkoxy moiety through some steric effects. For series 2, where the indolizine ring has been replaced by varying heterocyclic rings, along with the changes in aminoalkoxy moiety of the phenyl ring, the QSAR exhibits that these different heterocyclic rings affect both the activities through some steric roles, altering the conformations of the receptors from system A to system B. Among the different heterocyclic rings, the N-substituted indole ring is shown to be more conducive to both the activities than any other ring. However, a 5-membered ring is indicated to be less effective than a 9- or 10-membered ring for activity B. Additionally, the amino moieties having phenyl ring with methoxy groups at 3,4,and 5-positions are shown to favour both A and B activities.     

Synthesis, stereochemistry and biological activity of some novel long alkyl chain substituted thiazolidin-4-ones and thiazan-4-one from 10-undecenoic acid hydrazide

The synthesis of four novel compounds, (i) [(11-{[2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]amino}-11-oxoundecyl)sulfanyl]acetic acid (4), (ii) N-[5-methyl-2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]undec-10-enamide (5), (iii) 2-[(11-{[5-methyl-2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]amino}-11-oxoundecyl)sulfanyl]propanoic acid (6) and (iv) 3-[(11-{[2-(3-nitrophenyl)-4-oxo-1,3-thiazinan-3-yl]amino}-11-oxoundecenyl) sulfanyl]propanoic acid (8) from 10-undecenoic acid hydrazide (1) via m-nitrobenzaldehyde-10-undecenohydrazone (2) using mercaptoacetic acid in (i), 2-mercaptopropionic acid in (ii and iii) and 3-mercaptopropionic acid in (iv) is described. The uncyclized products, ({11-[(2E)-2-(3-nitrobenzylidene)hydrazino]-11-oxo-undecyl}sulfanyl)acetic acid (3) and 3-({11-[(2E)-2-(3-nitrobenzylidene)hydrazino]-11-oxoundecyl}sulfanyl)propanoic acid (7) are also obtained in (i) and (iv), respectively. The hydrazones (2), (3) and (7) exist in two conformers as synperiplanar and antiperiplanar. Structural assignment, stereochemistry and biological assays are discussed.     

Synthesis and leishmanicidal activities of 1-(4-X-phenyl)-N'-[(4-Y-phenyl)methylene]-1H-pyrazole-4-carbohydrazides

1H-pyrazole-4-carbohydrazides were synthesized and their leishmanicidal in vitro activities and cytotoxic effects were investigated. The drugs prototypes of these new compounds (ketoconazole, benznidazole, allopurinol and pentamidine) were also tested. It was found that among all the 1H-pyrazole-4-carbohydrazides derivatives examined, the most active compounds were those with X = Br, Y = NO2 (27) and X = NO2, Y = Cl (15) derivatives which showed to be most effective on promastigotes forms of L. amazonensis than on L. chagasi and L. braziliensis species. When tested against murine peritoneal macrophages as mammalian host cell controls of toxicity, 1-(4-Br-phenyl)-N'-[(4-NO(2)-phenyl)methylene]-1H-pyrazole-4-carbohydrazides (27) (EC50 = 50 microM l(-1)) and 1-(4-NO2-phenyl)-N'-[(4-Cl-phenyl)methylene]-1H-pyrazole-4-carbohydrazides (15) EC50 = 80 microM l(-1))] was reasonably toxic. However, both compounds were less toxic than pentamidine and ketoconazole. These results provide new perspectives on the development of drugs with activities against Leishmania parasite.     

Conformationally constrained analogues of N'-(4-tert-butylbenzyl)-N-(4-methylsulfonylaminobenzyl)thiourea as TRPV1 antagonists

A series of bicyclic analogues having indan and tetrahydronaphthalene templates in the A-region were designed as conformationally constrained analogues of our previously reported potent TRPV1 antagonists (1, 3). The activities for rat TRPV1 of the conformationally restricted analogues were moderately or markedly diminished, particularly in the case of the tetrahydronaphthalene analogues. The analysis indicated that steric constraints at the benzylic position in the bicyclic analogues may be an important factor for their unfavorable interaction with the receptor.     

Synthesis and pharmacology of the putative novel muscarinic agonist (S)-4-F-MePyMcN [(S)-4-(pyrrolidino)-1-methyl-2-butynyl-N-(4-fluorophenyl) carbamate oxalate]

(S)-4-F-MePyMcN [(S)-4-(pyrrolidino)-1-methyl-2-butynyl-N-(4-fluorophenyl) carbamate oxalate] has been suggested to be a selective agonist at the M₁ subtype of muscarinic receptor [Lambrecht G. et al., Life Sci. 56 (1995) 815–822]. We synthesized the compound and tested its selectivity for different muscarinic receptors with binding experiments using rat cerebral cortex synaptosomal membranes and cloned human m1 to m5 receptors and by functional experiments on rabbit vas deferens preparations. There was little difference in affinity for the compound at the different cloned muscarinic receptors (IC₅₀s for displacement of ³H-N-methylscopolamine were 0.7-1.0 μM). On rabbit vas deferens preparations, (S)-4-F-MePyMcN did reduce twitch responses to electrical stimulation like the known M₁ agonist McN-A-343, but unlike McN-A-343 the compound reduced postsynaptic sensitivity to noradrenaline, ATP and KCl. Because of these additional actions, (S)-4-F-MePyMcN may not be suitable as a tool to study M₁ muscarinic receptors selectively.     

Studies on metabolism of fungicide benzoic acid, 1,3-dithiolan-2-ylidenehydrazide in vitro]

The metabolism of fungicide benzoic acid, 1,3-dithiolan-2-ylidenehydrazied (Yekuling) was studied quantitatively in rat liver microsomes and liver soluble fractions pretreated with phenobarbital (PB) and 3-methylcholanthrene (3-MC) by high pressure liquid chromatography. The experimental results indicated that the major metabolic pathway of Yekuling in vitro was hydrolysis. PB can enhance amidase activity to increase formation of benzoic acid and 1,3-dithiolan-2-ylidenehydrazine. 3-MC treatment elevated rat liver microsomal cytochrome P-448, enhancing S-oxidation of Yekuling. On the other hand, S-oxidation of Yekuling by rat liver microsomal MFO was NADPH-dependent.     

Transition metal complexes of 2, 6-di ((phenazonyl-4-imino) methyl)-4-methylphenol: structure and biological evaluation

A symmetric ligand 2, 6-di ((phenazonyl-4-imino)methyl)-4-methylphenol (Dpmp) and its cobalt dinuclear complex (Co₂(Dpmp)₂(NO3)₂(H₂O)₂·NO3·EtOH, (1) and zinc mononuclear complex Zn(Dpmp)(NO₃)₂, (2) have been prepared. The crystal structures were determined by single-crystal X-ray diffraction. The biological activity has been evaluated by examining their anti-oxidative activity and ability to bind to bovine serum albumin (BSA) and calf-thymus DNA (CT DNA) with UV-vis absorption, fluorescence, viscosity measurements and circular dichroism (CD) spectroscopies. The complexes exhibit good binding propensity to BSA and CT DNA. Both 1 and 2 have been found to promote cleavage of pUC19 DNA in the absence of any reducing agent. Antioxidant tests in vitro show the compounds possess significant antioxidant activity against superoxide and hydroxyl radicals.     

Synthesis and anticonvulsant activity of new N-[(4-arylpiperazin-1-yl)-alkyl] derivatives of 3-phenyl-pyrrolidine-2,5-dione

In the present study, on the development of new anticonvulsants, the series of N-[(4-arylpiperazin-1-yl)-alkyl]-3-(2-methylphenyl)- (8a-e, 10a-h) and 3-(2-trifluoromethyl-phenyl)-pyrrolidine-2,5-diones (9a-e, 11a-i) were synthesized and tested for anticonvulsant activity using the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) screens. Their neurotoxicity were determined applying the rotorod test. In this series, the most active were N-[(4-phenylpiperazin-1-yl)-methyl]-3-(2-trifluoromethylphenyl)-pyrrolidine-2,5-dione (9a) with the ED(50)=20.78mg/kg, when given orally to rats and N-[3-{4-(3-trifluoromethylphenyl)-piperazin-1-yl}-propyl]-3-(2-trifluoromethylphenyl)-pyrrolidine-2,5-dione (11i) with the ED(50)=132.13mg/kg after intraperitoneally injection to mice.     

Synthesis and biological activity of novel N-cycloalkyl-(cycloalkylaryl)-2-[(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)thio]acetamides

In this paper the novel N-cycloalkyl-(cycloalkylaryl)-2-[(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)thio]acetamides synthesis by aminolysis of activated by thionyl chloride or carbonyldiimidazole [(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)-thio]acetic acids and alkylation of the 3-R-6-thio-6,7-dihydro-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones potassium salts with N-cycloalkyl-(cycloalkylaryl)-2-chloroacetamides are proposed. The structures of compounds are determined by ¹H, ¹³C NMR, LC-MS and EI-MS analysis. The in vitro anticancer, antibacterial activity and Photobacterium leiognathi Sh1 bioluminescence inhibition of synthesized compounds were revealed. SAR results were discussed. Compound 4.10 was found to be the most anticancer active one, selectively influenced on the non-small cell lung and CNS cancer cell lines, especially on the HOP-92 (log GI₅₀ = −6.01) and U251 (log GI₅₀ = −6.00).