Quinoline-based Compounds as Key Candidates to Tackle Drug Discovery Programs of Microbicidal Agents

Ultrasound assisted synthesis of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety with potential antimicrobial activity

We present in this paper a direct and efficient study regarding synthesis and spectral characterization of three series of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety, with potential antimicrobial activity, by using ultrasound (US) irradiation and conventional methods (CV). The synthesis pathway is efficient and direct, in two steps: an initial N-acylation of 8-aminoquinoline followed by metal complexation with variously M2+ metals (Cd2+, Co2+, Cu2+, Ni2+, Pd2+, Zn2+). For both type of reactions, N-acylation and complexation, under US irradiations the synthesis have some undeniable advantages: the most relevant being the higher yields, a dramatically decrease for reaction time (with about 150 (one hundred fifty) folds for complexation) comparative with conventional methods (CV) (therefore the spent energy decrease in the same way), a decrease of the amount of used solvents. Taking into account the above considerations these reactions setup could be appreciated as eco-friendly. The structures of the obtained hybrid quinoline - sulfonamide complexes (HQBSM) were determined by elemental analysis and by using spectral investigations: FT-IR, NMR experiments, and X-ray diffraction (in three cases). The FT-IR and NMR spectra of complexes show a similar spectroscopic pattern for all complexes and fully confirm the proposed structures. The X-ray spectra analyses prove without doubts the structure of metal complexes, indicating that their structure depends essentially by two factors: the nature of metal and the nature of sulfonamide-quinoline moieties. Complexes containing 4-methoxy-benzoyl moiety and Zn2+ (e.g. 6a) are tetra-coordinated while in the Ni2+ complex (e.g. 6e) the metallic ion forms a distorted square-based bi-pyramid. In the complexes containing 4-nitro-benzoyl moiety and Cd2+ (e.g. 5d) the metallic ion forms a triangular bipyramid. The antibacterial and antifungal assay reveal that only hybrid HQBSM complex (4e) (with 4-chlorophenyl moiety and Ni2+ in molecule) have a significant antibacterial activity.

Quinoline derivatives volunteering against antimicrobial resistance: rational approaches, design strategies, structure activity relationship and mechanistic insights

Emergence of antimicrobial resistance has become a great threat to human species as there is shortage of development of new antimicrobial agents. So, its mandatary to combat AMR by initiating research and developing new novel antimicrobial agents. Among phytoconstituents, Quinoline (nitrogen containing heterocyclic) have played a wide role in providing new bioactive molecules. So, this review provides rational approaches, design strategies, structure activity relationship and mechanistic insights of newly developed quinoline derivatives as antimicrobial agents.

The Potential of 2-Substituted Quinolines as Antileishmanial Drug Candidates

There is a need for new, cost-effective drugs to treat leishmaniasis. A strategy based on traditional medicine practiced in Bolivia led to the discovery of the 2-substituted quinoline series as a source of molecules with antileishmanial activity and low toxicity. This review documents the development of the series from the first isolated natural compounds through several hundred synthetized molecules to an optimized compound exhibiting an in vitro IC₅₀ value of 0.2 µM against Leishmania donovani, and a selectivity index value of 187, together with in vivo activity on the L. donovani/hamster model. Attempts to establish structure–activity relationships are described, as well as studies that have attempted to determine the mechanism of action. For the latter, it appears that molecules of this series act on multiple targets, possibly including the immune system, which could explain the observed lack of drug resistance after in vitro drug pressure. We also show how nanotechnology strategies could valorize these drugs through adapted formulations and how a mechanistic targeting approach could generate new compounds with increased activity.

Repurposing Bedaquiline for Effective Non-Small Cell Lung Cancer (NSCLC) Therapy as Inhalable Cyclodextrin-Based Molecular Inclusion Complexes

There is growing evidence that repurposed drugs demonstrate excellent efficacy against many cancers, while facilitating accelerated drug development process. In this study, bedaquiline (BDQ), an FDA approved anti-mycobacterial agent, was repurposed and an inhalable cyclodextrin complex formulation was developed to explore its anti-cancer activity in non-small cell lung cancer (NSCLC). A sulfobutyl ether derivative of β-cyclodextrin (SBE-β-CD) was selected based on phase solubility studies and molecular modeling to prepare an inclusion complex of BDQ and cyclodextrin. Aqueous solubility of BDQ was increased by 2.8 × 10³-fold after complexation with SBE-β-CD, as compared to its intrinsic solubility. Solid-state characterization studies confirmed the successful incorporation of BDQ in the SBE-β-CD cavity. In vitro lung deposition study results demonstrated excellent inhalable properties (mass median aerodynamic diameter: 2.9 ± 0.6 µm (<5 µm) and fine particle fraction: 83.3 ± 3.8%) of BDQ-CD complex. Accelerated stability studies showed BDQ-CD complex to be stable up to 3 weeks. From cytotoxicity studies, a slight enhancement in the anti-cancer efficacy was observed with BDQ-cyclodextrin complex, compared to BDQ alone in H1299 cell line. The IC₅₀ values for BDQ and BDQ-CD complex were found to be ~40 µM in case of H1299 cell line at 72 h, whereas BDQ/BDQ-CD were not found to be cytotoxic up to concentrations of 50 µM in A549 cell line. Taken together, BDQ-CD complex offers a promising inhalation strategy with efficient lung deposition and cytotoxicity for NSCLC treatment.