Quinoline-based promising anticancer and antibacterial agents, and some metabolic enzyme inhibitors

A series of substituted quinolines was screened for their antiproliferative, cytotoxic, antibacterial activities, DNA/protein binding affinity, and anticholinergic properties by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation, lactate dehydrogenase cytotoxicity, and microdilution assays, the Wolfe-Shimmer equality method, the Ellman method, and the esterase assay, respectively. The results of the cytotoxic and anticancer activities of the compounds displayed that 6-bromotetrahydroquinoline (2), 6,8-dibromotetrahydroquinoline (3), 8-bromo-6-cyanoquinoline (10), 5-bromo-6,8-dimethoxyquinoline (12), the novel N-nitrated 6,8-dimethoxyquinoline (13), and 5,7-dibromo-8-hydroxyquinoline (17) showed a significant antiproliferative potency against the A549, HeLa, HT29, Hep3B, and MCF7 cancer cell lines (IC₅₀  = 2-50 μg/ml) and low cytotoxicity (∼7-35%) as the controls, 5-fluorouracil and cisplatin. The compound-DNA linkages are hyperchromic or hypochromic, causing variations in their spectra. This situation shows that they can be bound to DNA with the groove-binding mode, with K_b value in the range of 2.0 × 10³ -2.2 × 10⁵  M^-1 . Studies on human Gram(+) and Gram(-) pathogenic bacteria showed that the substituted quinolines exhibited selective antimicrobial activities with MIC values of 62.50-250 μg/ml. All tested quinoline derivatives were found to be effective inhibitors of acetylcholinesterase (AChE) and the human carbonic anhydrase I and II isoforms (hCA I and II), with K_i values of 46.04-956.82 nM for hCA I, 54.95-976.93 nM for hCA II, and 5.51-155.22 nM for AChE. As a result, the preliminary data showed that substituted quinolines displayed effective pharmacological features. Molecular docking studies were performed to investigate the binding modes and interaction energies for compounds 2-17 with AChE (PDB ID: 4EY6), hCA I (PDB ID: 1BMZ), and hCA II (PDB ID: 2ABE).