Determination of the free radical scavenging activity of dihydropyran-2,4-diones

The antioxidant activities of four synthetic dihydropyran-2,4-diones have been established through the determination of their abilities to inhibit free radicals using DPPH(*) as the stable radical. Whilst all of the compounds exhibited high inhibition percentages, the most active member of the group was 6-phenyl-dihydropyran-2,4-dione. The antioxidant activity of the dihydropyran-2,4-diones is reported here for the first time and extends our knowledge of the range of valuable biological activities associated with this group of compounds.     

Identification of an ethyl 5,6-dihydropyrazolo[1,5-c]quinazoline-1-carboxylate as a catalytic inhibitor of DNA gyrase

Fluoroquinolones are a class of antibacterial agents used clinically to treat a wide array of bacterial infections and target bacterial type-II topoisomerases (DNA gyrase and topoisomerase IV). Fluoroquinolones, however potent, are susceptible to bacterial resistance with prolonged use, which limits their use in the clinic. Quinazoline-2,4-diones also target bacterial type-II topoisomerases and are not susceptible to bacterial resistance similar to fluoroquinolones, however, their potency pales in comparison to fluoroquinolones. To meet the increasing demand for antibacterial development, nine modified quinazoline-2,4-diones were developed to probe quinazoline-2,4-dione structure modification for possible new binding contacts with the bacterial type-II topoisomerase, DNA gyrase. Evaluation of compounds for inhibition of the supercoiling activity of DNA gyrase revealed a novel ethyl 5,6-dihydropyrazolo[1,5-c]quinazoline-1-carboxylate derivative as a modest inhibitor of DNA gyrase, having an IC₅₀ of 3.5 μM. However, this ethyl 5,6-dihydropyrazolo[1,5-c]quinazoline-1-carboxylate does not trap the catalytic intermediate like fluoroquinolones or typical quinazoline-2,4-diones do. Thus, the ethyl 5,6-dihydropyrazolo[1,5-c]quinazoline-1-carboxylate derivative discovered in this work acts as a catalytic inhibitor of DNA gyrase and therefore represents a new structural type of catalytic inhibitor of DNA gyrase.     

Thiazolidine-2,4-diones: Progress towards multifarious applications

The promising activity shown by compounds containing thiazolidine-2,4-dione nucleus in numerous categories such as anti-hyperglycaemics, aldose reductase inhibitors, anti-cancer, anti-inflammatory, anti-arthritics, anti-microbials, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substituents on the thiazolidine-2,4-dione nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, peroxisome proliferator activated receptor γ (PPARγ) agonism and PPARγ-dependent and -independent anti-cancer activities are reviewed separately in literature. Short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing thiazolidine-2,4-dione nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of thiazolidine-2,4-dione nucleus in medicinal chemistry research. In the present review, various derivatives of thiazolidine-2,4-diones with different pharmacological activities are described on the basis of substitution pattern around the nucleus combined with the docking studies performed in the active site of the corresponding receptors with an aim to help medicinal chemists for developing an SAR on thiazolidine-2,4-dione derived compounds for each activity. This discussion will further help in the development of novel thiazolidine-2,4-dione compounds.     

N-Acyl and N-sulfonyloxazolidine-2,4-diones are pseudo-irreversible inhibitors of serine proteases

The synthesis, inhibitory activity and mode of action of oxazolidine-2,4-diones against porcine pancreatic elastase, here used as a model for human neutrophil elastase, are reported. The nature of N-substitution at the oxazolidine-2,4-dione scaffold has large effect on the inhibitory potency against elastase. N-Acyl and N-sulfonyloxazolidine-2,4-diones emerged as potent pseudo-irreversible inhibitors, displaying high second-order rate constants for PPE inactivation. The title compounds were also shown to be potent inhibitors of human neutrophil elastase (HNE) and proteinase-3, and weak inhibitors of human cathepsin G. The results herein presented show that the oxazolidine-2,4-diones represent a new promising class of serine protease inhibitors.     

Dual action spirobicycloimidazolidine-2,4-diones: Antidiabetic agents and inhibitors of aldose reductase-an enzyme involved in diabetic complications

The desired 3-(arylsulfonyl)spiroimidazolidine-2,4-diones were synthesized by reacting spiroiminoimidazolidine-2,4-dione with arylsulfonyl chlorides. Spiroimidazolidine-2,4-dione was in turn synthesized from norcamphor. Structures of the synthesized molecules were established by modern spectroscopic techniques. The synthesized compounds were screened for in vivo antidiabetic activity and aldose reductase inhibition. Compounds 2a, 2b and 2g exhibited excellent dual activity, compound 2a being most prominent. These results reveal that the synthesized compounds may serve as the molecule of choice to treat diabetes and diabetic complications using a single medication.     

Replacement of methoxatin by 4,7-phenanthroline-5,6-dione and the inability of other phenanthroline quinones, as well as 7,9-di-decarboxy methoxatin, to serve as cofactors for the methoxatin-requiring glucose dehydrogenase of Acinetobacter calcoaceticus

Glucose dehydrogenase from A. calcoaceticus has been dissociated into apoenzyme and methoxatin coenzyme, and enzyme activity restored by replacing coenzyme with 4,7-phenanthroline-5,6-dione but not with 1,10- nor 1,7-phenanthroline-5,6-diones nor with 7,9-decarboxy methoxatin.     

Inhibitory effects of multi-substituted benzylidenethiazolidine-2,4-diones on LDL oxidation

Multi-substituted benzylidenethiazolidine-2,4-diones 3a-h were synthesized by Knoevenagel condensation of di- or tri-substituted 4-hydroxybenzaldehydes [or 1-(3,5-di-tert-butyl-4-hydroxyphenyl)ethanone] 1 with thiazolidine-2,4-dione (2) and evaluated for antioxidant activities of Cu(2+)-induced oxidation of human low-density lipoproteins (LDL). Among compounds 3a-h, 3a was superior to probucol in LDL-antioxidant activities and found to be ninefold more active than probucol. Due to its potency, compound 3a was tested for complementary in vitro investigations, such as TBARS assay (IC(50) = 0.1 microM), lag time (240 min at 1.5 microM), relative electrophoretic mobility (REM) of ox-LDL (inhibition of 83% at 10 microM), fragmentation of apoB-100 (inhibition of 61% at 5 microM), and radical DPPH scavenging activity on copper-mediated LDL oxidation. In macrophage-mediated LDL oxidation, the TBARS formation was also inhibited by compound 3a.     

Synthesis and biological evaluation of benzimidazole-4,7-diones that inhibit vascular smooth muscle cell proliferation

A series of 6-arylamino-5-chloro-benzimidazole-4,7-diones were synthesized and tested for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. Among them, 6-arylamino-5-chloro-2-methyl-benzimidazole-4,7-diones exhibited potent antiproliferative activity. Benzimidazole-4,7-dione 2c activated SAPK/JNK signaling pathway in the RAoSMCs.     

Synthesis, biological active molecular design, and molecular docking study of novel deazaflavin-cholestane hybrid compounds

Novel deazaflavin-cholestane hybrid compounds, 3',8'-disubstituted-5'-deazacholest-2,4-dieno[2,3-g]pteridine-2',4'(3'H,8'H)-diones, have been synthesized by condensation reaction between 6-(monosubstituted amino)-pyrimidin-2,4(1H,3H)-diones and 2-hydroxymethylenecholest-4-en-3-one in presence of p-toluenesulfonic acid monohydrate and diphenyl ether. The antitumor activities against human tumor cell lines (CCRF-HSB-2 and KB cells) have been investigated in vitro, and many of these compounds showed promising antitumor activities. Furthermore, molecular docking study using LigandFit within the software package Discovery Studio 1.7 was done for lead optimization of these compounds as potential PTK inhibitors. In general, all of the synthesized steroid-hybrid compounds showed good binding affinities into PTK (PDB code: 1t46).     

Evaluation of Antituberculosis Activity and in Silico Properties of Oxymethylene-cyclo-1,3-diones

Tuberculosis is a leading infectious disease that has infected one-third of the world's population and is more prevalent among people belonging to developing countries such as India and China. In the present study, a series of substituted oxymethylene-cyclo-1,3-diones was synthesized and screened for anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv (M. tuberculosis). The compounds were synthesized by condensation of 1,3-cyclicdione, substituted phenols/ alcohols and triethyl orthoformate. The synthesized compounds were screened for anti-tuberculosis activity against M.tuberculosis H37Rv using Middlebrook 7H9 broth assay. Results demonstrated that among the synthesized library of molecules, two compounds 2-(2-hydroxyphenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 5,5-dimethyl-2-(2-trifluoromethylphenoxymethylene)cyclohexane-1,3-dione were found to be most active against M. tuberculosis (MICs of 1.25 μg/mL⁻¹). The MICs of 2-(2,4-difluoro-phenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 2-(2-bromophenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione were found to be 5 and 10 μg mL⁻¹, respectively. Data from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all the four most active compounds did not exhibit cytotoxicity against human cell lines. Molecular docking studies revealed that the most active compound targets mycobacterial InhA enzyme. In summary, the present study demonstrates the methodology for the synthesis of oxymethylene-cyclo-1,3-diones and identified two potential anti-tuberculosis compounds.     

Synthesis and anticonvulsant activity of new N-Mannich bases derived from 5-cyclopropyl-5-phenyl- and 5-cyclopropyl-5-(4-chlorophenyl)-imidazolidine-2,4-diones

Synthesis, physicochemical and anticonvulsant properties of new N-Mannich bases derived from 5-cyclopropyl-5-phenyl- and 5-cyclopropyl-5-(4-chlorophenyl)-imidazolidine-2,4-diones have been described. Initial anticonvulsant screening was performed using intraperitoneal (ip.) maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The neurotoxicity was determined applying the rotarod test. The in vivo results in mice showed that all compounds were effective especially in the MES screen. The quantitative evaluation after oral administration in rats showed that the most active was 5-cyclopropyl-5-phenyl-imidazolidine-2,4-dione (1) with ED(50) values of 5.76 mg/kg (MES) and 57.31 mg/kg (scPTZ). This molecule was more potent than phenytoin and ethosuximide which were used as reference antiepileptic drugs. Additionally compound 1 with ED(50) of 26.06 mg/kg in psychomotor seizure test (6-Hz) in mice showed comparable activity to new generation anticonvulsant - levetiracetam.     

Synthesis and biological evaluation of quinoxaline-5,8-diones that inhibit vascular smooth muscle cell proliferation

A series of 6-arylamino-2,3-bis(pyridin-2-yl)-7-chloro-quinoxaline-5,8-diones were synthesized and evaluated for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. The quinoxaline-5,8-diones exhibited a potent antiproliferative activity. Further mechanistic study revealed that the inhibitory effect of one representative quinoxaline-5,8-dione on SMC proliferation was mediated by modulation of the extracellular signal-regulated kinase 1/2 signaling pathway in the RAoSMCs.     

Synthesis of 6-arylvinyl analogues of the HIV drugs SJ-3366 and Emivirine

This paper reports the synthesis and the antiviral activities of a series of 6-arylvinyl substituted analogues of SJ-3366, a highly potent agent against HIV. The objective was to investigate whether substitution of the 6-arylketone with a 6-arylvinyl group could lead to an improved antiviral activity against HIV-1. The most active compounds 1-ethoxymethyl, 1-(2-propynyloxymethyl), and 1-(2-methyl-3-phenylallyloxymethyl) substituted 6-[1-(3,5-dimethylphenyl)vinyl]-5-ethyl-1H-pyrimidine-2,4-dione (5b, 16, and 18) showed activities against HIV-1 wild type in the range of Efavirenz, and moderate activities against Y181C and Y181C+K103N mutant strains were also observed.     

Synthesis and biological evaluation of 5-arylamino-1H-benzo[d]imidazole-4,7-diones as inhibitor of endothelial cell proliferation

5-Arylamino-1H-benzo[d]imidazole-4,7-diones were synthesized and tested for their inhibitory activities on the proliferation of human umbilical vein endothelial cells (HUVECs) and the smooth muscle cells (SMCs). Among them, several 1H-benzo[d]imidazole-4,7-diones exhibited the selective antiproliferative activity on the HUVECs. Further mechanistic study revealed that the inhibitory effect of one representative 1H-benzo[d]imidazole-4,7-dione 2b on HUVEC proliferation was mediated by the activation of p38 signaling pathway in the HUVECs.     

2,4-Diaryl-5,6-dihydro-1,10-phenanthroline and 2,4-diaryl-5,6-dihydrothieno[2,3-h] quinoline derivatives for topoisomerase I and II inhibitory activity, cytotoxicity, and structure-activity relationship study

Designed and synthesized thirty-two 2,4-diaryl-5,6-dihydro-1,10-phenanthroline and 2,4-diaryl-5,6-dihydrothieno[2,3-h] quinoline derivatives as rigid analogs of 2,4,6-trisubstituted pyridines were evaluated for topoisomerase I and II inhibitory activities as well as cytotoxicities against several human cancer cell lines. Structure-activity relationship study showed that [2,2';6',2"]-terpyridine skeleton is important for the cytotoxicity against several human cancer cell lines.     

Antimycobacterial evaluation of novel hybrid arylidene thiazolidine-2,4-diones

A series of novel hybrid heterocycles comprising arylidene thiazolidine-2,4-dione and 1-cyclopropyl-2-(2-fluorophenyl)ethanone were synthesized. These compounds were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H₃₇Rv in High Throughput Screen. Most of the hybrid arylidene thiazolidine-2,4-diones displayed moderate to good activity with MIC of less than 50 μM. Compound 1m exhibited maximum potency being 5.87 fold more active at EC₅₀ and 6.26 fold more active at EC₉₀ than the standard drug pyrimethamine.     

Synthesis and in vitro evaluation of pteridine analogues as monoamine oxidase B and nitric oxide synthase inhibitors

Monoamine oxidase B (MAO-B) and nitric oxide synthase (NOS) have both been implicated in the pathology of neurodegenerative diseases. In an attempt to design dual-target-directed drugs that inhibit both these enzymes, a series of pteridine-2,4-dione analogues were synthesised. The compounds were found to be relatively weak NOS inhibitors but showed promising MAO-B activity with 6-amino-5-[(E)-3-(3-chloro-phenyl)-prop-2-en-(E)-ylideneamino]-1,3-dimethyl-1H-pyrimidine-2,4-dione and 6-[(E)-2-(3-chloro-phenyl)-vinyl]-1,3-dimethyl-1H-pteridine-2,4-dione inhibiting MAO-B with IC₅₀ values of 0.602 and 0.314 μM, respectively. The pteridine-2,4-dione analogues thus show promise as scaffolds for the development of potent reversible MAO-B inhibitors and as observed in earlier studies, the most potent inhibitors were obtained with 3-chlorostyryl substitution.     

Mixed-ligand Ru(II) complexes with 2,2'-bipyridine and aryldiazo-beta-diketonato auxillary ligands: synthesis, physico-chemical study and antitumour properties

The complexes of Ru(II)-2,2'-bipyridyl with substituted diazopentane-2,4-diones (L1H-L5H) were synthesized and characterized by elemental analyses, conductance, FAB (fast atom bombardment) mass and spectral (IR, UV/Vis (UV/visible), NMR) studies. Molecular geometry optimization of the complexes was also made. None of the complexes luminesce. However, facilitated oxidation of Ru(II) to Ru(III) was evidenced from their lower reduction potential data. The ligands and their complexes were tested for their antitumour activity against a variety of tumour cell lines. Though activity is found to vary with the type of tumour cell lines used, yet complex 5 with naphtyldiazopentane-2,4-dione as co-ligand was found to be a potential compound as it showed in general significant activity against all cell lines studied.     

Synthesis and antifungal activity of 6-hydroxycinnolines

6-Hydroxycinnolines 2 and cyclohexa-2,5-diene-1,4-dione derivatives 6 were synthesized and tested for in vitro antifungal activity against Candida and Aspergillus species. 6-Hydroxycinnolines 2 showed, in general, more potent antifungal activity against Candida species than the other cyclohexa-2,5-diene-1,4-diones. The results suggest that 6-hydroxycinnolines would be potent antifungal agents.     

3-hydroxy-quinazoline-2,4-dione as a useful scaffold to obtain selective Gly/NMDA and AMPA receptor antagonists

The synthesis and Gly/NMDA, AMPA and KA receptor binding activities of some 3-hydroxy-quinazoline-2,4-dione derivatives are reported. The binding data, together with functional antagonism studies, showed that the 3-hydroxy-quinazoline-2,4-dione moiety can be considered a useful scaffold to obtain selective Gly/NMDA and AMPA receptor antagonists. In fact, introduction of chlorine atom(s) on precise position(s) of the benzofused moiety yielded Gly/NMDA selective antagonists, while the presence of the 6-(1,2,4-triazol-4-yl) group shifted the affinity and selectivity towards the AMPA receptor.