Antibacterial activity of CTBT (7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine) generating reactive oxygen species

Self-Catalyzed Rapid Synthesis of N-Acylated/N-Formylated α-Aminoketones and N-Hydroxymethylated Formamides from 3-Aryl-2H-Azirines and 2-Me/Ph-3-Aryl-2H-Azirines

A rapid and effective method has been established for the synthesis of N-acylated α-aminoketone derivatives by the reaction of 3-aryl-2H-azirines and highly substituted 2-Me/Ph-3-aryl-2H-azirines with various carboxylic acids under ambient air within 10 min at room temperature. N-Trifluoroacetylated α-aminoketones with different substituents have been reported in the presence of trifluoroacetic acid. This protocol is equally effective to synthesize N-formylated α-aminoketone and N-hydroxymethylated formamide derivatives.

Synthesis and anticancer evaluation of some novel pyrimido[5,4-e][1,2,4]triazines and pyrazolo[3,4-d]pyrimidine using DMF-DMA as methylating and cyclizing agent

Background

Described a series of main target compounds pyrimido[5,4-e][1,2,4]triazines is obtained via condensation of 6-hydrazinyluracil with different aromatic aldehydes to give the hydrazones followed by nitrosation with HNO₂ then intramolecular cyclization. On the other hand, pyrazolopyrimidines can be obtained by the reaction of hydrazones with dimethylformamide-dimethylacetal (DMF-DMA), DMF-DMA in the presence of DMF or by refluxing the hydrazinyluracil with DMF-DMA in the presence of DMF directly. The newly synthesized compounds are evaluated in vitro for their anticancer activity against human lung carcinoma (A549).

Results

A newly substituted compounds of benzaldehyde-pyrimidin-4-yl)hydrazones (5a–f), pyrimido[5,4-e][1,2,4]triazines 6a–e, arylethylidenehydrazinylpyrimidine 7a,b and pyrazolopyrimidines 9,11 are screened for cytotoxic activity against human lung carcinoma (A549) cell line. They exhibited a good yield. Compound 6b shows the highest effect with IC₅₀ value 3.6 μM, followed by compounds 9, 5a, 8, 5e, 6e, 5b, 5f, 7a, 5c, 6c, 7b, 6a, 11, 5d and 6d.

Conclusion

A simple and efficient route is used for the synthesis of pyrimido[5,4-e][1,2,4]triazines and pyrazolopyrimidines. The synthesized compounds are screened for antitumor activity.

Cytochromes bd-I and bo3 are essential for the bactericidal effect of microcin J25 on Escherichia coli cells

Microcin J25 has two targets in sensitive bacteria, the RNA polymerase, and the respiratory chain through inhibition of cellular respiration. In this work, the effect of microcin J25 in E. coli mutants that lack the terminal oxidases cytochrome bd-I and cytochrome bo₃ was analyzed. The mutant strains lacking cytochrome bo₃ or cytochrome bd-I were less sensitive to the peptide. In membranes obtained from the strain that only expresses cytochrome bd-I a great ROS overproduction was observed in the presence of microcin J25. Nevertheless, the oxygen consumption was less inhibited in this strain, probably because the oxygen is partially reduced to superoxide. There was no overproduction of ROS in membranes isolated from the mutant strain that only express cytochrome bo₃ and the inhibition of the cellular respiration was similar to the wild type. It is concluded that both cytochromes bd-I and bo₃ are affected by the peptide. The results establish for the first time a relationship between the terminal oxygen reductases and the mechanism of action of microcin J25.

Antibacterial activity of Syzygium aromaticum seed: Studies on oxidative stress biomarkers and membrane permeability

Oxidative stress and membrane permeability as mode of antibacterial activity of aqueous extract of Syzygium aromaticum seeds against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus was investigated. The concentration of phytochemical constituents of Syzygium aromaticum was determined using gas chromatography. Syzygium aromaticum seeds contain eugenol acetate > β-carophyllene > eugenin > eugenol > methyl salicylate > β-humulene > rhamnatin > fernesol > α-copeane > β-ylangene > kaempferol > cinnamic acid > oleanolic acid > benzaldehyde > α-humulene > vanillin > α-cubebene > carvicol > benzoic acid. Syzygium aromaticum showed antimicrobial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values as 0.06 and 0.10 mg/mL respectively. Time kill susceptibility by Syzygium aromaticum at MBC values showed significant decrease in the optical density and colony-forming unit (CFU) of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Superoxide anion radical content of the bacterial cells increased significantly following exposure to the extract. In a similar vein, superoxide dismutase and catalase activities increased significantly, while the level of reduced glutathione reduced, malondialdehyde increased significantly in bacterial cells exposed to the extract. The extract at MBC also enhanced the leakage of 260 nm absorbing materials and outer membrane permeability. It is evident from the data generated from this study that aqueous extract of Syzygium aromaticum seeds enhanced membrane permeability and oxidative stress in Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Evaluation of Antibacterial Activity and Reactive Species Generation of N-Benzenesulfonyl Derivatives of Heterocycles

Two N-benzenesulfonyl (BS) derivatives of 1,2,3,4-tetrahydroquinoline (THQ) were designed, prepared, and screened for antibacterial activity. This approach was based on combining the two privileged structures, BS and THQ, which are known to be active. The objective of this study was to evaluate the antibacterial activity of BS-THQ and its analogue 4-NH2BS-THQ, and to investigate the roles of reactive oxygen species and reactive nitrogen species in their lethality. Both showed bactericidal activity against Staphylococcus aureus ATCC 29213 and methicillin-resistant S. aureus (MRSA) ATCC 43300, with transmission electron microscopy revealing a disturbed membrane architecture. Furthermore, an increase of reactive oxygen species (ROS) in strains treated with BS-THQ with respect to the control was detected when fluorescent microscopy and spectrophotometric techniques were used. The analogue 4-NH2BS-THQ demonstrated a broader spectrum of activity than BS-THQ, with a minimum inhibitory concentration of 100 µg/mL against reference strains of S. aureus, Escherichia coli and Pseudomonas aeruginosa. The assayed compounds represent promising structures for the development of new synthetic classes of antimicrobials.