Flavoenzyme-mediated reduction reactions and antitumor activity of nitrogen-containing tetracyclic ortho-quinone compounds and their nitrated derivatives

Nitrogen-based tetracyclic ortho-quinones (naphtho[1'2':4.5]imidazo[1,2-a]pyridine-5,6-diones, NPDOs) and their nitro-substituted derivatives (nitro-(P)NPDOs) were obtained by condensation of substituted 2,3-dichloro- 1,4-naphthoquinones with 2-amino-pyridine and -pyrimidine and nitration at an elevated temperature. The structural features of the compounds as well as their global and regional electrophilic potency were characterized by means of DFT computation. The compounds were highly reactive substrates of single- and two-electron (hydride)- transferring P-450R (CPR; EC 1.6.2.4) and NQO-1 (DTD; EC 1.6.99.2), respectively, concomitantly producing reactive oxygen species. Their catalytic efficiency defined in terms of the apparent second-order rate constant (kcat/KM (Q)) values in P-450R- and NQO-1-mediated reactions varied in the range of 3-6 × 107 M-1 s-1 and 1.6-7.4 × 108 M-1 s-1, respectively. The cytotoxic activities of the compounds on tumor cell lines followed the concentration-dependent manner exhibiting relatively high cytotoxic potency against breast cancer MCF-7, with CL50 values of 0.08-2.02 µM L-1 and lower potency against lung cancer A-549 (CL50 = 0.28-7.66 µM L-1). 3-nitro-pyrimidino- NPDO quinone was the most active compound against MCF-7 with CL50 of 0.08 ± 0.01 µM L-1 (0.02 µg mL-1)) which was followed by 3-nitro-NPDO with CL50 of 0.12 ± 0.03 µM L-1 (0.035 µg mL-1)) and 0.28 ± 0.08 µM L-1 (0.08 µg mL-1) on A-549 and MCF-7 cells, respectively, while 1- and 4-nitro-quinoidals produced the least cyto- or cells quantified by AO/EB staining showed that the cell death induced by the compounds occurs primarily through apoptosis

Preliminary investigation of the antibacterial activity of antitumor drug 3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine) and its derivatives

The antitumor drug 3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine, TPZ (1)) along with a number of newly synthesized tirapazamine derivatives (TPZs) bearing substitutions at the 3-amine position of TPZ (1) were estimated for their antibacterial activity against representative Gram-negative Escherichia coli (ATCC 25922) and Salmonella enterica (SL 5676), as well as Gram-positive Staphylococcus aureus (ATCC 25923) bacterial strains. Their activities in terms of minimum inhibitory concentrations (MICs) varied in the range of 1.1 M (0.25 g/mL)–413 M (128 g/mL). Amongst the most potent derivatives (1–6), acetyl- and methoxycarbonyl-substituted TPZs (2 and 4) were the strongest agents, which exhibited approximately 4–30 fold greater activities compared to those of TPZ (1) along with the reference drugs chloramphenicol (CAM) and nitrofurantoin (NFT). The inhibitory activities of the compounds were highly impacted by their structural features. No reliable relationships were established between activities and the electron-accepting potencies of the whole set of studied compounds, while the activities of TPZ drug (1) and the structurally uniform set of molecules (2–6) were found to increase with an increase in their electron-accepting potencies obtained by means of density functional theory (DFT) computation. A greater steric, lipophilic and polar nature of the substituents led to a lower activity of the compounds. The combined antibacterial in vitro trial gave clear evidence that TPZs coupled with the commonly utilized antibiotics ciprofloxacin (Cipro) and nitrofurantoin (NFT) could generate enhanced (suggestive of partial and virtually complete synergistic) and additive e ects. The strongest e ects were defined for TPZs–NFT combinations, which resulted in a notable reduction in the MICs of di-N-oxides. These preliminary findings suggest that the synthesized novel di-N-oxides might be used as sole agents or applied as antibiotic complements

New 1-(3-nitrophenyl)-5,6-dihydro-4H-[1,2,4]triazolo[4,3- a][1,5]benzodiazepines: synthesis and computational study

Triazole derivatives constitute an important group of heterocyclic compounds have have been the subject of extensive study in the recent past. These compounds have shown a wide range of biological and pharmacological activities. In this work, new fused tricyclic 1-(3-nitrophenyl)-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1,5]-benzodiazepines have been synthesized by the thermal cyclization of N'-(2,3-dihydro-1H-1,5-benzodiazepin-4-yl)-3- nitrobenzohydrazides. After screening ethanol, toluene and 1-butanol as solvents, butanol-1 was found to be the best choice for the cyclization reaction in order to obtain the highest yields of tricyclic derivatives. The chemical structures of the synthesized compounds were elucidated by the analysis of their IR, 1H- and 13C-NMR spectral data. For tentative rationalization of the reaction processes, the global and local reactivity indices of certain compounds, taking part in the reaction pathway, were assessed by means of quantum mechanical calculations using the conceptual density functional theory (DFT) approach. This work could be useful for the synthesis of new heterocyclic compounds bearing a fused triazole ring