H. R. Prakash Naik

Nanostructured TiO2 Catalyzed Microwave Assisted Synthesis of Fused Quinolines – DNA Binding, Molecular Docking and Antioxidant Activity

The use of nanostructured TiO2 as mixed phase photocatalyst in the synthesis of 2H-pyrano/2H-thiopyrano [2,3-b]quinoline-2-carboxylic acid (2a/2b) is described. The binding modes of 2a/2b with ds DNA fragments d(CGCGAATTCGCG) were predicted by molecular docking studies. The lowest energy was found in the compound 2b with a binding energy of -7.44 Kcal/mol and inhibition constant of 5.39 x e-6. The interaction study with CT DNA was carried out by absorption spectra, (Kb constant obtained for 2a is 3.5x106 and for 2b it is 2.9x105), viscosity and thermal denaturation methods. The in vitro antioxidant activities were evaluated. Finally, the results showed that the intercalated 2a/2b compounds are strong antioxidants and they protect oxidative DNA damage from harmful free radicals.

Pyrimido[4,5-b]quinoline-2-thiol/ol: microwave-induced one-pot synthesis, DNA binding and cleavage studies

This article describes the synthesis of pyrimido[4,5-b]quinoline-2-thiol/ol (3a/3b) by microwave irradiation technique. The dynamic interaction of compounds with deoxyribonucleic acid (DNA) was investigated by absorption spectra, viscosity measurements, and thermal denaturation studies. Intrinsic binding constants (K b ) had values 3.1×106 for 3a and 2.3×105 for 3b. The proposed DNA binding mode supports the large enhancement in the relative viscosity of calf thymus (CT-DNA) on binding to compounds. Results suggest that 3a/3b can bind to CT-DNA by intercalation via the aromatic ring into the base pairs of DNA. Moreover, efficient DNA damage was observed on oxidative cleavage in the presence of 3a/3b.

2-Thieno/Selenopyrano[2,3-b]quinolines: Microwave-Induced One-Pot Synthesis, DNA Binding, and Photocleavage Studies

We have characterized a new class of 2-thieno/2-selenopyrano[2,3-b]quinolin-2-ol (2c/3c) intercalators exhibiting a novel type of DNA binding and photocleavage activity. The dynamic behavior of these compounds with DNA was investigated by absorption spectra (obtained Kb constant for 2c is 3.6 × 106 and for 3c is 2.8 × 105), viscosity, and thermal denaturation studies. Intrinsic binding constants (Kb) have been estimated under a similar set of experimental conditions. An absorption spectral study shows the strong interaction between synthesized 2c, 3c, and base pairs CT-DNA. In addition, the effects of these compounds on DNA cleavage were investigated by photoirradiation at 360 nm and show that the hybrids effectively cleaved double-stranded DNA with UV light of a long wavelength and without any additive.

Synthesis, DNA Binding, Docking and Photoclevage Studies of Novel Benzo[b][1,8]naphthyridines

The synthesis and docking studies of novel benzo[b][1,8]naphthyridines is discribed. The docking studies show that the derivatives prefer to bind the AT-rich region of double stranded DNA (ds-DNA). The maximum binding energy -7.16 (kcal/mol) was observed for benzo[b][1,8]naphthyridine-5-thiol 5a and it is a better candidate as an enantioselective binder to ds-DNA than the other derivatives of benzo[b][1,8]naphthyridines. When photoirradiated at 365 nm, benzo[1,8]-naphthyridines have been found to promote the photocleavage of plasmid pUC19 DNA.

Benzo[h]quinoline based Macrocyclic Copper(II), Cobalt(II) Complexes: Synthesis, Characterization and Light induced DNA Cleavage Studies

A new ligand dibenzo[h]quinolineno[1,3,7,9] tetraazacyclododecine-7,15 (14H, 16H)-dibenzene (L) and its Co(II)/Cu(II) metal complexes of type [MLX2] (Where (M = Co(II) (5), Cu(II) (6) and X = Cl) were synthesized and are well characterized by FT-IR, 1H-NMR, FAB mass elemental analysis, and electronic spectral data. The role of the cobalt/copper metals in photo-induced DNA cleavage reactions was explored by designing complex molecules having macrocyclic structure. Finally, we have shown that photocleavage of plasmid DNA is more efficiently enhanced when this macrocyclic ligand is irradiated in the presence of copper(II) than that of cobalt metal.

Synthesis of Quinoline-Based Thieno-Seleno-Phenylquinazolinones

The synthesis of quinoline-substituted phenylquinazolinones containing sulfur and selenium is described. These molecules were isolated from a series of reactions of 2-phenyl-4H-3,1-benzoxazin-4-one with 2-chloro, 2-thieno, and 2-selenoquinoline-3-carbaldehyde hydrazones. The structure of the isolated compounds has been elucidated on the basis of IR, 1 H NMR, mass spectral, and elemental analysis data.

An Efficient, Microwave-Assisted, One-Pot Synthesis of Dioxolano Quinoline/benzo[h]quinolines as Potent Antibacterial Agents

Quinolines/benzo[h]quinolines are associated with a broad spectrum of biological activities. In view of this, 3-(1,3-dioxolan-2-yl)quinoline/benzo[h]quinoline-2-thiol/selenols were prepared under microwave irradiation through one-pot reactions, and these quinolines/ benzo[h]quinolines were evaluated for potential antibacterial activity. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

TiO2 Nanopowder Catalyzed Microwave-Induced One-Pot Synthesis of Novel Quinoline/Benzo[h]quinoline3-carbonitrile Under Solvent Free Conditions

A rapid and efficient method for the synthesis of various carbonitrile quinoline/benzo[h]quinolines has been developed through the Knoevenagel condensation, Michael addition of aromatic aldehyde/amine with carbonyl compounds in the presence of a nanostructured TiO2 photocatalyst by microwave irradiation under solvent-free conditions.

A Rapid and Efficient Multicomponent Synthesis of Bi-Quinolines Under Solvent-Free Conditions

An efficient synthesis of substituted condensed quinolino-quinolines has been achieved in a one-pot reaction from 2-hydroxy/mercapto/seleno-4-methylquinoline and 2-mercapto/seleno-3-formyl quinolines using anhydrous ammonium hydroxide as the reductant by microwave irradiation under solvent-free conditions.

Synthesis, Characterization, and DNA Binding Studies of S2N2 Donor Bis-Mercaptoquinoline Co(II) and Ni(II) Metal Complexes: A New Class of Antimicrobial Agent

This article describes a convenient procedure for the synthesis of metal complexes of the type [ML] [CoMPQT](1), [NiMPQT](2) where M = Co(II), Ni(II) tetradentate (S2N2) Schiff-base using 3-[(2-[(2-mercaptoquinolin-3-yl)methylene]aminophenyl)imino]methyl quinoline-2-thiol ligand (MPQT)L. The synthesized ligand and its metal complexes were characterized by elemental analysis, FT-IR, 1H NMR, mass, and electronic spectra. The mode of bonding and the geometry of the complexes have been confirmed on the basis of IR and UV-vis spectral findings and magnetic measurements. The binding property of the complexes with calf-thymus DNA was studied by absorption spectra, viscosity measurements, and thermal denaturation studies. The intrinsic binding constant (Kb) had the value 2.8 × 104 M−1 for 1 and 4.8 × 104 M−1 for 2, suggesting that complex 2 binds more strongly to CT-DNA than complex 1. The synthesized metal complexes were screened for antibacterial and antifungal activities. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.