Design, synthesis, molecular docking, and spectral studies of new class of carbazolyl polyhydroquinoline derivatives as promising antibacterial agents with noncytotoxicity towards human mononuclear cells from peripheral blood

Synthesis of hydrazone-based polyhydroquinoline derivatives - antibacterial activities, α-glucosidase inhibitory capability, and DFT study

In recent years, polyhydroquinolines have gained much attention due to their widespread applications in medicine, agriculture, industry, etc. Here, we synthesized a series of novel hydrazone-based polyhydroquinoline derivatives via multi-step reactions. These molecules were characterized by modern spectroscopic techniques (1H-NMR, 13C NMR, and LC-HRMS) and their antibacterial and in vitro α-glucosidase inhibitory activities were assessed. Compound 8 was found to be the most active inhibitor against Listeria monocytogenes NCTC 5348, Bacillus subtilis IM 622, Brevibacillus brevis, and Bacillus subtilis ATCC 6337 with a zone of inhibition of 15.3 ± 0.01, 13.2 ± 0.2, 13.1 ± 0.1, and 12.6 ± 0.3 mm, respectively. Likewise, compound 8 also exhibited the most potent inhibitory potential for α-glucosidase (IC50 = 5.31 ± 0.25 μM) in vitro, followed by compounds 10 (IC50 = 6.70 ± 0.38 μM), and 12 (IC50 = 6.51 ± 0.37 μM). Furthermore, molecular docking and DFT analysis of these compounds showed good agreement with experimental work and the nonlinear optical properties calculated here indicate that these compounds are good candidates for nonlinear optics.

Antimicrobial activity of natural and semi-synthetic carbazole alkaloids

Since the first natural carbazole alkaloid, murrayanine, was isolated from Mwraya Spreng, carbazole alkaloid derivatives have been widely concerned for their anti-tumor, anti-viral and anti-bacterial activities. In recent decades, a growing body of data suggest that carbazole alkaloids and their derivatives have different biological activities. This is the first comprehensive description of the antifungal and antibacterial activities of carbazole alkaloids in the past decade (2012-2022), including natural and partially synthesized carbazole alkaloids in the past decade. Finally, the challenges and problems faced by this kind of alkaloids are summarized. This paper will be helpful for further exploration of this kind of alkaloids.

Hantzsch reaction using copper nitrate hydroxide-containing mesoporous silica nanoparticle with C3N4 framework as a novel powerful and reusable catalyst

Copper nitrate hydroxide (CNH)-containing mesoporous silica nanoparticle (MSN) with g-C₃N₄ framework (MSN/C₃N₄/CNH) was fabricated via a four-step hydrothermal synthesis method. Functionalized MSN-based C₃N₄ was prepared, decorated with CNH, and identified by different physicochemical techniques such as FT-IR, XRD, SEM, EDX, and STA analyses. Then, MSN/C₃N₄/CNH composite was utilized as a robust catalyst for the fast fabrication of biologically active polyhydroquinoline derivatives with high yields between 88 and 97% via Hantzsch reaction under mild reaction conditions and short reaction time (within 15 min) owing to synergistic influence of Lewis acid and base sites. Moreover, MSN/C₃N₄/CNH can be straightforwardly recovered and used up to six reaction cycles without a conspicuous decrease in efficiency.

Novel Polyhydroquinoline-Hydrazide-Linked Schiff's Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (3-27) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (1-27) were deduced with the help of spectroscopic techniques, such as 1H-, 13C -NMR, and HR-ESI-MS. The synthesized products (1-27) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of Escherichia coli and Enterococcus faecalis. Among them, compound 17 was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound 27 was more potent, with an EC50 value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.

Design, synthesis, spectral characterization and molecular docking studies of novel pyranoquinolinyl dihydropyridine carboxylates as potential antibacterial agents including Vibrio cholerae with minimal cytotoxity towards fibroblast cell line (L-929)

Novel pyranoquinolinyl dihydropyridine carboxylate (PDC) derivatives were designed by incorporating the multi-drug resistance modulating effects of 1,4 dihydropyridines along with potential antibacterial activity of quinolines in the molecular design. The designed PDC derivatives were synthesized by multi-step synthesis involving Michael addition, reduction followed by inverse electro demand Diels-Alder reaction to produce pyranoquinolinyl dihydropyridine carboxylates in good yields. All the PDC derivatives were characterized by ¹H NMR, ¹³C NMR, FT-IR, Mass spectral and CHN analysis. The Quinolinyl dihydropyridine carboxylate derivatives were evaluated for in vitro antibacterial activity by agar well diffusion method. Molecular docking studies revealed that the exo diethyl 4-(4aR,5S,10bR)-5-(4-chlorophenyl)-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinolin-8-yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate diastereomer (5c) forms four hydrogen bonds with the cell wall protein of vibrio cholerae in comparison to the endo diethyl 4-((4aR,5R,10bR)-5-(4-chlorophenyl)-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinolin-8-yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate diastereomer (4c) which forms two hydrogen bonds with the cell wall protein of vibrio cholerae and hence leading to better anchorage, enhanced gold score and relatively good antibacterial activity for the exo PDC derivatives. Minimum inhibitory concentration (MIC) of the active compounds was evaluated by macro dilution method. The mechanism of antibacterial action of the PDC derivatives was investigated by SEM studies. The cytotoxicity of PDC derivatives were evaluated against fibroblast cells (L-929).