The resistance of pathogenic microbes to currently available antimicrobial agents has been considered a global alarming concern. Hence, close attention should be paid to the development of novel potent antimicrobials. Herein, we report the synthesis, in vitro antimicrobial evaluation, of two novel sets of quinoline derivatives as potential DNA gyrase and DHFR inhibitors. The design of new compounds depended on modifying the structural aspects of previously reported fluoroquinolones. In both sets, the methyl group replaced the fluorine atom at C-6. In the first set, the diverse heterocyclic fragments of reported antimicrobial potentials, including pyrazole, isoxazole, and pyrimidine, were attached to C-3 of the quinoline scaffold. In the second set, the quinolone ring was replaced with the pyrazolo[3,4-b]quinoline scaffold to examine the effect of this action on the antimicrobial activity and the in silico virtual binding with DNA gyrase and DHFR. The preliminary antimicrobial activity of new compounds was assessed against a panel of pathogenic microbes including Gram-positive bacteria (Streptococcus pneumonia and Bacillus subtilis), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), and fungal strains (Aspergillus fumigatus, Syncephalastrum racemosum, and Geotriucum candidum). Six derivatives displayed relatively potent antimicrobial activity with a percent activity range of 80–113% relative to ampicillin, gentamicin, and amphotericin B as reference antimicrobial agents. Molecular docking studies were conducted to predict the binding affinities of new compounds toward the active sites of DNA gyrase and DHFR as proposed therapeutic targets.

Treatment options for the management of breast cancer are still inadequate. This inadequacy is attributed to the lack of effective targeted medications, often resulting in the recurrence of metastatic disorders. Cumulative evidence suggests that epidermal growth factor receptor (EGFR-TK) and cyclin-dependent kinases-9 (CDK-9) overexpression correlates with worse overall survival in breast cancer patients. Pyranopyrazole and pyrazolone are privileged options for the development of anticancer agents. Inspired by this proven scientific fact, we report here the synthesis of two new series of suggested anticancer molecules incorporating both heterocycles together with their characterization by IR, ¹H NMR, ¹³C NMR, ¹³C NMR-DEPT, and X-ray diffraction methods. An attempt to get the pyranopyrazole-gold complexes was conducted but unexpectedly yielded benzylidene-2,4-dihydro-3H-pyrazol-3-one instead. This unexpected result was confirmed by X-ray crystallographic analysis. All newly synthesized compounds were assessed for their anti-proliferative activity against two different human breast cancer cells, and the obtained results were compared with the reference drug Staurosporine. The target compounds revealed variable cytotoxicity with IC₅₀ at a low micromolar range with superior selectivity indices. Target enzyme EGFR-TK and CDK-9 assays showed that compounds 22 and 23 effectively inhibited both biological targets with IC₅₀ values of 0.143 and 0.121 µM, respectively. Molecular docking experiments and molecular dynamics simulation were also conducted to further rationalize the in vitro obtained results. Communicated by Ramaswamy H. Sarma

In this study, an efficient multistep synthesis of novel aromatic tricyclic hybrids incorporating different biological active moieties, such as 1,3,4-thiadiazole and 1,2,4-triazole, was reported. These target scaffolds are characterized by having terminal lipophilic or hydrophilic parts, and their structures are confirmed by different spectroscopic methods. Further, the cytotoxic activities of the newly synthesized compounds were evaluated using in vitro MTT cytotoxicity screening assay against three different cell lines, including HepG-2, MCF-7, and HCT-116, compared with the reference drug Taxol. The results showed variable performance against cancer cell lines, exhibiting MCF-7 and HepG-2 selectivities by active analogs. Among these derivatives, 1,2,4-triazoles 11 and 13 and 1,3,4-thiadiazole 18 were found to be the most potent compounds against MCF-7 and HepG-2 cancer cells. Moreover, structure–activity relationship (SAR) studies led to the identification of some potent LSD1 inhibitors. The tested compounds showed good LSD1 inhibitory activities, with an IC₅₀ range of 0.04–1.5 μM. Compounds 27, 23, and 22 were found to be the most active analogs with IC₅₀ values of 0.046, 0.065, and 0.074 μM, respectively. In addition, they exhibited prominent selectivity against a MAO target with apparent cancer cell apoptosis, resulting in DNA fragmentation. This research provides some new aromatic-centered 1,2,4-triazole-3-thione and 1,3,4-thiadiazole analogs as highly effective anticancer agents with good LSD1 target selectivity.