Novel aryl-bis-quinolines with antimalarial activity in-vivo

Potent Antimalarial Activity of Two Arenes Linked with Triamine Designed To Have Multiple Interactions with Heme

Based on the idea that compounds designed to exhibit high affinity for heme would block hemozoin formation, a critical heme-detoxification process for malarial parasites, we synthesized a series of compounds with two π-conjugated moieties at terminal amino groups of triamine. These compounds exhibited moderate to high antimalarial activities in vitro toward both chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum. In a P. berghei-infected mouse model, 3a and 12a showed potent antimalarial activities compared to artesunate, as well as a prolonged duration of antimalarial effect. We found a good correlation between protective activity against hemin degradation and antimalarial activity. Compounds 8b and 3a strongly inhibited hemozoin formation catalyzed by heme detoxification protein.

New 2-(aryl/heteroaryl)-6-(morpholin-4-yl/pyrrolidin-1-yl)-(4-trifluoromethyl)quinolines: synthesis via Buchwald–Hartwig amination, photophysics, and biomolecular binding properties

New 6-(morpholino/pyrrolidino)quinolines displaying interesting photophysical and biomolecular binding properties achieved by Buchwald–Hartwig amination.

Comprehensive review on various strategies for antimalarial drug discovery

The resistance of malaria parasites to existing drugs carries on growing and progressively limiting our ability to manage this severe disease and finally lead to a massive global health burden. Till now, malaria control has relied upon the traditional quinoline, antifolate and artemisinin compounds. Very few new antimalarials were developed in the past 50 years. Among recent approaches, identification of novel chemotherapeutic targets, exploration of natural products with medicinal significance, covalent bitherapy having a dual mode of action into a single hybrid molecule and malaria vaccine development are explored heavily. The proper execution of these approaches and proper investment from international agencies will accelerate the discovery of drugs that provide new hope for the control or eventual eradication of this global infectious disease. This review explores various strategies for assessment and development of new antimalarial drugs. Current status and scientific value of previous approaches are systematically reviewed and new approaches provide a pragmatic forecast for future developments are introduced as well.

Vibrational spectroscopic and molecular docking study of (2E)-N-(4-chloro-2-oxo-1,2-dihydroquinolin-3-yl)-3-phenylprop-2-enamide

FT-IR and FT-Raman spectra of (2E)-N-(4-chloro-2-oxo-1,2-dihydroquinolin-3-yl)-3-phenylprop-2-enamide were recorded and analyzed experimentally and theoretically. The synthesis, (1)H NMR and PES scan results are also discussed. Nonlinear optical behavior of the examined molecule was investigated by the determination of first hyperpolarizability. The calculated HOMO and LUMO energies show the chemical activity of the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. From the MEP it is evident that the negative charge covers the carbonyl group and the positive region is over the NH group. The calculated geometrical parameters (SDD) are in agreement with that of similar derivatives. Molecular docking simulations against targets from Mycobacterium tuberculosis are reported and the results suggest that the compound might exhibit inhibitory activity against PknB.

Experimental and theoretical studies on IR, Raman, and UV-Vis spectra of quinoline-7-carboxaldehyde

Spectroscopic properties of quinoline-7-carboxaldehyde (Q7C) have been studied in detail both experimentally and theoretically. The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)), dispersive-Raman (3500-50 cm(-1)), and UV-Vis (200-400 nm) spectra of Q7C were recorded at room temperature (25 °C). Geometry parameters, potential energy surface about CCH(O) bond, harmonic vibrational frequencies, IR and Raman intensities, UV-Vis spectrum, and thermodynamic characteristics (at 298.15K) of Q7C were computed at Hartree-Fock (HF) and density functional B3LYP levels employing the 6-311++G(d,p) basis set. Frontier molecular orbitals, molecular electrostatic potential, and Mulliken charge analyses of Q7C have also been performed. Q7C has two stable conformers that are energetically very close to each other with slight preference to the conformer that has oxygen atom of the aldehyde away from the nitrogen atom of the quinoline.

Spectroscopic (FT-IR, FT-Raman, UV and NMR) investigation, conformational stability, NLO properties, HOMO-LUMO and NBO analysis of hydroxyquinoline derivatives by density functional theory calculations

The FTIR and FT-Raman spectra of 2-hydroxyquinoline and its derivatives have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of these compounds were obtained by the density functional theory using 6-311++G(d,p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. A detailed interpretation of the infrared and Raman spectra were also reported based on total energy distribution (TED). The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically simulated spectra. (1)H and (13)C NMR spectra were recorded and its corresponding nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compound was recorded and the electronic properties HOMO and LUMO energies were measured by time-dependent (TD-DFT) approach. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. In addition, the non-linear optical properties were discussed from the dipole moment values and excitation wavelength in the UV-visible region.

Vibrational spectra of quinoline-4-carbaldehyde: combined experimental and theoretical studies

The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)) and Dispersive-Raman (3500-50 cm(-1)) spectra of solid sample of quinoline-4-carbaldehyde (Q4C) have been recorded. The molecule structure, vibrational frequencies, IR intensities, Raman intensities and thermodynamic properties of the two possible aldehyde rotamers of Q4C have been obtained with the Hartree-Fock (HF) and density functional B3LYP calculations employing the 6-311++G(d,p) basis set. Q4C has two stable conformers, in one of which the O atom of the aldehyde is oriented to form a H-bond with one of the hydrogens of quinoline, while in the other there is no such a H bond. The conformer with an extra H-bond is more stable and, thus it is the ground state. The computed vibrational frequencies of the lowest energy conformer agree also slightly better than those of the higher energy rotamer with the experimental frequencies after the computed frequencies are scaled. The temperature dependence of the standard heat capacities (C), standard entropies (S) and standard enthalpy (H) changes of Q4C has been discussed.

Tetrazole-based deoxyamodiaquines: synthesis, ADME/PK profiling and pharmacological evaluation as potential antimalarial agents

A series of new deoxyamodiaquine-based compounds was synthesized via the modified TMSN3-Ugi multi-component reaction and evaluated in vitro for antiplasmodial activity. The most potent compounds, 6b, 6c and 6j, showed IC50 values in the range of 6-77nM against chloroquine-resistant K1- and W2-strains of Plasmodium falciparum. In vitro ADME characterization of frontrunner compounds 6b and 6c indicates that these two compounds are rapidly metabolized and have a high clearance rate in human and rat liver microsomes. This result correlated well with an in vivo pharmacokinetics study, which showed low bioavailability of 6c in rats. Tentative metabolite identification was determined by LC-MS and suggested metabolic lability of groups attached to the tertiary nitrogen. Preliminary studies on 6b and 6c suggested strong inhibitory activity against the major CYP450 enzymes. In silico docking studies were used to rationalize strong inhibition of CYP3A4 by 6c. Full characterization and biological evaluation of the metabolites is currently underway in our laboratories.

Experimental and theoretical quantum chemical investigations of 8-hydroxy-5-nitroquinoline

The FT-IR and FT-Raman spectra of 8-hydroxy-5-nitroquinoline have been recorded in the regions 4000-400 and 4000-100 cm(-1), respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The normal coordinate analysis was carried out to confirm the precision of the assignments. The structure of the compound was optimised and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(**), 6-311++G(**) and cc-pVDZ basis sets. The vibrational frequencies were calculated in all these methods and were compared with the experimental frequencies which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. (1)H and (13)C NMR spectra were recorded and (1)H and (13)C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-Visible spectrum of the compound was recorded and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. The influences of the nitro and hydroxy groups on the skeletal modes and on the proton chemical shifts have been investigated.

Determination of structural and vibrational properties of 6-quinolinecarboxaldehyde using FT-IR, FT-Raman and dispersive-Raman experimental techniques and theoretical HF and DFT (B3LYP) methods

The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)) and Dispersive-Raman (3500-50 cm(-1)) spectra of solid sample of 6-quinolinecarboxaldehyde (6QC) have been recorded. The structure, vibrational frequencies, IR intensities, Raman activities and thermodynamic properties of the two possible aldehyde rotamers of 6QC have been calculated at the Hartree-Fock (HF) and density functional B3LYP levels employing 6-311++G(d,p) basis set. The complete assignments were performed on the basis of the potential energy distribution (PED) of the all vibrational modes. Since HF and B3LYP mode definitions of this molecule are quite similar to each other, we only give in Table 3 PED of Rot1 calculated at B3LYP level for the sake of simplicity. Potential energy surface has been scanned over the C3-C2-C1O16 torsion angle. When the O atom of the aldehyde is farther away than the nitrogen atom of the quinoline, 6QC has the lowest possible energy, and thus is in its ground state. The scaled theoretical frequencies of the lowest energy rotamer agree also slightly better than those of the higher energy rotamer with the experimental frequencies. The thermodynamic characteristics of the ground state of 6QC have been theoretically investigated at 298.15 K temperature.

Quantum chemical and spectroscopic investigations of 5-aminoquinoline

The Fourier transform infrared (FTIR) and FT-Raman spectra of 5-aminoquinoline (5AQ) have been recorded in the range 4000-400 and 3500-100 cm(-1), respectively. The complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out using the observed FTIR and FT-Raman data. (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by using the gauge independent atomic orbital (GIAO) method. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The geometric parameters, chemical shifts and absorption wavelengths were compared with the experimental data of the molecule. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from ab initio HF and DFT-B3LYP gradient calculations employing the 6-31G** and 6-311++G** basis sets for optimized geometries of the compound. The interactions of NH-pi and the influence of amino group on the skeletal modes are investigated.

Ab initio, density functional theory and structural studies of 4-amino-2-methylquinoline

The Fourier transform infrared (FTIR) and FT-Raman spectra of 4-amino-2-methylquinoline (AMQ) have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. The experimental vibrational frequency was compared with the wavenumbers obtained theoretically by ab initio HF and DFT-B3LYP gradient calculations employing the standard 6-31 G** and high level 6-311 ++G** basis sets for optimised geometry of the compound. The complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out using the experimental FTIR and FT-Raman data, and quantum mechanical studies. The geometry and normal modes of vibration obtained from the HF and DFT methods are in good agreement with the experimental data. The potential energy distribution of the fundamental modes was calculated with ab initio force fields utilising Wilson's FG matrix method. The NH-pi interactions and the influence of amino and methyl groups on the skeletal modes are investigated.

Vibrational spectroscopic investigations, ab initio and DFT studies on 7-bromo-5-chloro-8-hydroxyquinoline

The Fourier transform infrared (FTIR) and FT-Raman spectra of 7-bromo-5-chloro-8-hydroxyquinoline (BCHQ) have been measured in the range 4000-400 and 4000-100cm(-1), respectively. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT-Raman data. The geometry was optimised without any symmetry constrains using the DFT/B3LYP and HF methods with 6-31G** basis set. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from ab initio HF and density functional theory (DFT) gradient calculations employing the HF/6-31G** and B3LYP/6-31G** methods for the optimised geometry of the compound. The structural parameters and normal modes of vibration obtained from HF and DFT methods are in good agreement with the experimental data. Normal coordinate analysis was also carried out with ab initio force fields utilising Wilson's FG matrix method.

Antimalarial in-vivo activity of bis(9-amino-6-chloro-2-methoxyacridines)

In the fight against malaria, chemotherapy using bisacridines may represent an alternative method to overcoming chloroquine-resistance. Eight bis(9-amino-6-chloro-2-methoxyacridines), in which acridine moieties were linked by polyamines substituted with a side chain, were tested for their in-vivo activity upon mice infected by Plasmodium berghei. Three of the compounds revealed antimalarial activity but no relationship could be deduced from a comparison of in-vitro and in-vivo activities. N-alkylation of the central amino group generated toxicity and, therefore, only compounds N-acylated in this position can be selected as leads.