Effect of 2,4-dihydro-3H-1,2,4-triazole-3-thiones and thiosemicarbazones on iodide uptake by the mouse thyroid: the relationship between their structure and anti-thyroid activity

Severe acute respiratory syndrome coronavirus replication inhibitor that interferes with the nucleic acid unwinding of the viral helicase

Severe acute respiratory syndrome (SARS) is a highly contagious disease, caused by SARS coronavirus (SARS-CoV), for which there are no approved treatments. We report the discovery of a potent inhibitor of SARS-CoV that blocks replication by inhibiting the unwinding activity of the SARS-CoV helicase (nsp13). We used a Förster resonance energy transfer (FRET)-based helicase assay to screen the Maybridge Hitfinder chemical library. We identified and validated a compound (SSYA10-001) that specifically blocks the double-stranded RNA (dsRNA) and dsDNA unwinding activities of nsp13, with 50% inhibitory concentrations (IC(50)s) of 5.70 and 5.30 μM, respectively. This compound also has inhibitory activity (50% effective concentration [EC(50)] = 8.95 μM) in a SARS-CoV replicon assay, with low cytotoxicity (50% cytotoxic concentration [CC(50)] = >250 μM), suggesting that the helicase plays a still unidentified critical role in the SARS-CoV life cycle. Enzyme kinetic studies on the mechanism of nsp13 inhibition revealed that SSYA10-001 acts as a noncompetitive inhibitor of nsp13 with respect to nucleic acid and ATP substrates. Moreover, SSYA10-001 does not affect ATP hydrolysis or nsp13 binding to the nucleic acid substrate. SSYA10-001 did not inhibit hepatitis C virus (HCV) helicase, other bacterial and viral RNA-dependent RNA polymerases, or reverse transcriptase. These results suggest that SSYA10-001 specifically blocks nsp13 through a novel mechanism and is less likely to interfere with the functions of cellular enzymes that process nucleic acids or ATP. Hence, it is possible that SSYA10-001 inhibits unwinding by nsp13 by affecting conformational changes during the course of the reaction or translocation on the nucleic acid. SSYA10-001 will be a valuable tool for studying the specific role of nsp13 in the SARS-CoV life cycle, which could be a model for other nidoviruses and also a candidate for further development as a SARS antiviral target.

Antioxidant, pro-oxidant effect of the thiosemicarbazone derivative Schiff base (4-(1-phenylmethylcyclobutane-3-yl)-2-(2-hydroxybenzylidenehydrazino) thiazole) and its metal complexes on rats

Adverse biological activities of thiosemicarbazone (TSC) and Schiff base (SB) derivatives have been widely studied in rats and in other animal species using different doses, times and routes of administration. However, there are few studies describing changes in some biochemical parameters in vivo which are indicative of oxidative stress in biological systems and of morphological changes of tissues. In this study, the rats were injected subcutaneously with a new thiosemicarbazone thiazole ring containing a Schiff base (LH) and its Cu(L)2 and Zn(L)2 complexes (25 mg kg(-1) body weight) and then sacrificed after 1, 2, 4, 8, 16, 32 and 64 days. The aim of this study was to determine the effect of the new compounds on the serum antioxidant vitamins (A, E, C), selenium (Se), malondialdehyde (MDA) levels, erythrocyte GSH-Px enzyme activity and morphological changes in the liver, kidney and adrenal gland tissues. It was observed that erythrocyte GSH-Px activity, serum MDA and vitamins A, E concentrations were statistically changed (p < 0.02), but serum levels of selenium, and vitamin C were not changed. In conclusion, the parameters measured show that Cu(L)2 caused considerable oxidative stress and Zn(L)2 behaved as an antioxidant. No oxidative stress in LH was observed compared to the control group.

Studies on nitrophenylfuran derivatives part Xii. synthesis, characterization, antibacterial and antiviral activities of some nitrophenylfurfurylidene-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines

Synthesis of four 1-aryl-3-[5-(p-nitrophenyl)-2-furyl]-2-propen-1-ones starting from substituted acetophenones and p-nitrophenylfurfuraldehyde is described. These propenones were then converted into corresponding dibromo derivatives which on dehydrobromination afforded alpha-bromopropenones rather than acetylenic ketones. Condensation of these dibromopropanones with 4-amino-5-mercapto-1,2,4-triazoles yielded a new class of nitrophenylfurfurylidene-1,2,4-triazolothiadiazines. The structures of nitrophenylfurfurylidene-1,2,4-triazolothiadiazines were established on the basis of analytical, IR, NMR and mass spectral studies. The formation of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines rather than 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazepines in the above condensation was unambiguously confirmed by X-ray crystallographic analysis of one of them. A possible mechanism is proposed to account for the formation of nitrophenylfurfurylidene-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines. Some of the newly synthesized triazolothiadiazines were screened for their antibacterial and antiviral properties.

The in vivo metabolism of 5-(4-nitrophenyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione in rats

It is known that substituted 1,2,4-triazole-3-thione derivatives have several biological activities, such as antimicrobial, diuretic and antidepressant activities. In our previous studies, the antifungal activity of 5-(4-aminophenyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione was found to be active against Candida tropicalis K1022. The aim of this study was to investigate the in vivo metabolic pathway of 5-(4-nitrophenyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione which was selected as a model compound for this study. The substrate and its potential metabolites, i.e. the acetylation and nitro reductive products, were synthesized and then separated using HPLC on a reverse phase system. In the in vivo metabolism study, a 4 mg dose was administered i.p. to male Wistar rats. Blood samples were collected at 0, 2, 4, 8, 12, 24 and 56 hours after administration and were passed through a Sep-Pak cartridge. The acetylated metabolite [5-(4-acetylaminophenyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione ], the amine metabolite [5-(4-aminophenyl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione] and an unknown metabolite were detected.