Novel Quinoline-Based Thiazole Derivatives for Selective Detection of Fe3+, Fe2+, and Cu2+ Ions.

New quinoline-based thiazole derivatives QPT and QBT were synthesized and characterized by various spectroscopic and single-crystal X-ray crystallographic studies. The metal-sensing properties of the probes were further examined by absorption and fluorescence spectrometry. The fluorescence intensity of QPT and QBT was remarkably quenched during the addition of Fe3+, Fe2+, and Cu2+ ions in THF/H2O (1:1) at pH = 7.4 in HEPES buffer, while the addition of other metal ions did not affect the fluorescence intensity of the ligands. The detection ability of the probes QPT and QBT was further investigated by titration with various equivalents of metal ions, optimized pH ranges for detection, and reversibility with Na2EDTA for biological applications.

Application of real sample analysis and biosensing: Synthesis of new naphthyl derived chemosensor for detection of Al3+ ions.

A new chemosensor (NANH) based on naphthyl moiety was synthesized with good selectivity and sensitivity towards Al3+ ions via the inhibition by operating through dual mechanisms like photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT). The synthesized NANH was validated by various techniques such as 1H, 13C NMR and mass spectrum. While prominent fluorescent enhancement was observed from the NANH upon binding with Al3+ ions, however, other metal ions have not responded in the emission spectrum. Detection limit and association constant of NANH for Al3+ were calculated as 1.2 × 10-7 M and 4.09 × 104 M-1 by using fluorescence titration method. Binding ratio (1:1) of NANH with Al3+ ions were proved by Job's plot and DFT studies. Furthermore, aluminium in variety of water samples was determined, and NANH could be used for biosensing of Al3+ in living cells.

A novel 8-nitro quinoline-thiosemicarbazone analogues induces G1/S & G2/M phase cell cycle arrest and apoptosis through ROS mediated mitochondrial pathway.

A series of novel 8-nitro quinoline-based thiosemicarbazone analogues were synthesized and characterized by various spectroscopic and single crystal X-ray analyses. The potent antitumor effects of synthesized compounds towards the cancer cells were evaluated by MTT assay. Amongst, the compound 3a exhibited the highest inhibitory activity and the compounds 3f and 3b were also showed significant activity. The molecular mechanistic studies of cell death have demonstrated that the treated potent compound 3a induced G1/S & G2/M phase cell cycle arrest and induced apoptosis via mitochondrial dysfunction and increased the production of cytotoxic ROS levels. The RT-PCR gene expression analysis revealed that the cell death induced by activation of caspase-3 dependent intrinsic apoptotic signaling pathway. Further, the molecular binding affinity of compounds with estrogen receptor alpha was calculated by molecular docking studies. Thus, novel 8-nitro quinoline-thiosemicarbazone analogues provide a unique tool for breast cancer therapeutic tactics.

Synthesis and X-ray study of dispiro 8-nitroquinolone analogues and their cytotoxic properties against human cervical cancer HeLa cells.

A series of unique dispiro analogues containing an oxindole pyrrolidine 8-nitroquinolone hybrid has been obtained through a one-pot three-component 1,3-dipolar cycloaddition of azomethine ylides generated in situ from the condensation of isatins and benzylamine with (E)-3-arylidene-2,3-dihydro-8-nitro-4-quinolones. The structures of the newly synthesized compounds were characterized by using different spectroscopic techniques and by X-ray diffraction studies of their regio- and stereochemistry. All the synthesized compounds were screened for in vitro cytotoxic activity against the human cervical cancer cell line HeLa. The compounds have exhibited potent inhibition against human cervical cancer cells and insignificant toxicity to normal cells. The compounds 6d, 6a, 6h, 6b, and 6e induced apoptosis of HeLa cells, through ROS influx. The expression levels of proteins involved in the mitochondrion-related pathways were detected, and Western blot analysis showed that apoptosis occurred via activation of caspase-3.

An efficient new dual fluorescent pyrene based chemosensor for the detection of bismuth (III) and aluminium (III) ions and its applications in bio-imaging.

A new simple pyrene based schiff base chemosensor 1 (nicotinic acid pyren-1-ylmethylene-hydrazide) has been constructed and is prepared from 1-pyrenecarboxaldehyde and nicotinic hydrazide. Notably, the chemosensor 1 exhibited remarkable colour changes while in the presence of trivalent metal ions like Bi3+ & Al3+ ion in DMSO-H2O, (1:1 v/v, HEPES = 50 mM, pH = 7.4). The UV-Vis spectral investigation of chemosensor 1 showed that the maximum absorption peak appeared at 378 nm. In emission studies, chemosensor 1 develops weak fluorescence, while upon the addition of Bi3+ and Al3+ ions, it exhibits an enhancement of fluorescence intensity. Nevertheless, rest of metal ions have no changes in the emission spectra. The association constant of chemosensor 1 for binding to Bi3+ & Al3+ system had a value of 1.27 × 104 M-1 and 1.53 × 104 M-1. The detection limits were 0.12 µM for Bi3+ and 0.17 µM for Al3+ respectively. The overall results reveal that chemosensor 1 can act as a dual-channel, highly selective, and sensitive probe for Bi3+ and Al3+ ions. Moreover, the fluorescence imaging of chemosensor 1 was applied in RAW 264.7 cell line and cytotoxicity assay prove that this chemosensor 1 is non-toxic as well as highly biocompatible.

Biologically active perspective synthesis of heteroannulated 8-nitroquinolines with green chemistry approach.

A new class of pyrazolo[4,3-c]quinoline (5a-i, 7a-b) and pyrano[3,2-c]quinoline (9a-i) derivatives were designed and synthesized in moderate to good yields by microwave conditions. To enhance the yield of pyrano[3,2-c]quinoline derivatives, multicomponent one-pot synthesis has been developed. The synthesized compounds were identified by spectral and elemental analyses. Compounds 9a and 9i showed good antibacterial activity against Gram-positive and Gram-negative bacterial strains. All of the new compounds exhibited weak to moderate antioxidant activity, compound 9d exerted significant antioxidant power. The cytotoxicity of these compounds were also evaluated against MCF-7 (breast) and A549 (Lung) cancer cell lines. Most of the compounds displayed moderate to good cytotoxic activity against these cell lines. Compound 9i was found to be significantly active in this assay and also induced cell death by apoptosis. Molecular docking studies were carried out using EGFR inhibitor in order to determine the molecular interactions.

Synthesis of first ever 4-quinolone-3-carboxylic acid-appended spirooxindole-pyrrolidine derivatives and their biological applications.

A series of 4-quinolone-3-carboxylic acid-containing spirooxindole-pyrrolidine derivatives was synthesized via multicomponent 1,3-dipolar cycloaddition reactions of azomethine ylides with new (E)-4-oxo-6-(3-phenyl-acryloyl)-1,4-dihydroquinoline-3-carboxylic acids in good yields with high regioselectivity. The cycloadducts were characterized by analytical and spectral data including [Formula: see text], [Formula: see text], 2D NMR and mass spectroscopy. The structure of one of the compounds (8a) was investigated theoretically by computational techniques. DFT studies support the proposed mechanism for this cycloaddition reaction. Furthermore, antibacterial activities of the new compounds were evaluated against Gram-positive and Gram-negative bacterial strains. Compounds 8f, 8m and 8p showed potent inhibition activities against selected bacteria. The in vitro cytotoxicity of spirooxindole derivatives (8a-r) was evaluated against MCF-7 breast cancer cell line. Among the various compounds tested, compound 8f [Formula: see text] showed significant cytotoxic activity compared to the standard drug doxorubicin [Formula: see text].

A new DNA-intercalative cytotoxic allylic xanthone from Swertia corymbosa.

Phytochemical investigation of the CHCl3 fraction of Swertia corymbosa resulted in the isolation of a new 3-allyl-2,8-dihydroxy-1,6-dimethoxy-9H-xanthen-9-one (1), along with four known xanthones, gentiacaulein (3), norswertianin (4), 1,3,6,8-tetrahydroxyxanthone (5), and 1,3-dihydroxyxanthone (6). Structure of compound 1 was elucidated with the aid of IR, UV, NMR, and MS data, and chemical transformation via new allyloxy xanthone derivative (2). Compounds 1-6 exhibited various levels of antioxidant and anti-α-glucosidase activities. Absorption and fluorescence spectroscopic studies on 1-6 indicated that these compounds could interact with calf thymus DNA (CT-DNA) through intercalation and with bovine serum albumin (BSA) in a static quenching process. Compound 1 was found to be significantly cytotoxic against human cancer cell lines HeLa, HCT116, and AGS, and weakly active against normal NIH 3T3 cell line.

Crystal structure of 4'-(2-meth-oxy-quinolin-3-yl)-1'-methyl-dispiro-[indan-2,2'-pyrrolidine-3',3''-indoline]-1,3,2''-trione.

In the title compound, C30H23N3O4, the central 1-methyl-pyrrolidine ring adopts a twist conformation on the N-CH2 bond. The pyrrolidin-2-one ring of the indolin-2-one ring system also has a twist conformation on the C-C bond involving the spiro C atom and the carbonyl C atom. The five-membered ring of the indene-1,3-dione moiety has an envelope conformation with the spiro C atom as the flap. The quinoline ring system adopts an almost planar conformation (r.m.s. deviation = 0.04 Å). The mean planes of the indolin-2-one ring system, the indene-1,3-dione ring system and the the quinoline ring system are inclined to the mean plane of the central 1-methyl-pyrrolidine ring by 77.97 (7), 86.98 (7) and 46.58 (6)°, respectively. In the crystal, mol-ecules are linked via N-H⋯N hydrogen bonds, forming chains along the b axis. The chains are linked via a number of C-H⋯O hydrogen bonds, and C-H⋯π and π-π inter-actions [inter-centroid distance = 3.7404 (9) Å], forming a three-dimensional network.

A regioselective multicomponent protocol for the synthesis of novel bioactive 4-hydroxyquinolin-2(1H)-one grafted monospiropyrrolidine and thiapyrrolizidine hybrids.

An expedient route toward the synthesis of 4-hydroxyquinolone grafted spiropyrrolidines or pyrrolizidines has been accomplished through 1,3-dipolar cycloaddition reaction of various azomethine ylides derived from isatin or acenaphthalene and sarcosine with 4-hydroxyquinolone derivatives as dipolarophile. The regio and stereo chemical outcome of the cycloaddition reaction is ascertained by X-ray crystallographic studies and spectroscopic techniques of the cycloadducts. Furthermore, cytotoxicity evaluation of selected compounds showed significant inhibition of cell proliferation against cervical as well as colon cancer cell lines.

Axially chiral biscarbazoles and biological evaluation of the constituents from Murraya koenigii.

Chemical investigation of the fruit pulp of Murraya koenigii resulted in the identification of two new dimeric carbazole alkaloids, bisgerayafoline D (1) and bismahanimbinol (2) along with four known alkaloids, bispyrayafoline (3), O-methyl mahanine (4), O-methyl mukonal (5), and mahanine (6). Structures of 1-6 were determined with the aid of UV, IR, Mass and extensive NMR spectroscopic studies. Absolute configurations of biaryls in 1 and 2 were assigned using a combination of computational Circular Dichroism (CD) and experimental electronic CD spectroscopic data. Compounds 1-6 were evaluated for anti-oxidant, anti-α-glucosidase, DNA binding, protein interactions and cytotoxic activities. Among all the isolates, mahanine (6) was found to exhibit significant radical scavenging and α-glucosidase inhibitory activities. Compound 6 was also found to be active in cytotoxicity assay against three human cancer cell lines HeLa, HCT116, AGS and this compound was weakly active against normal mouse embryonic fibroblasts (NIH3T3).

Antioxidant and structure-activity relationships of five tetraoxygenated xanthones from Swertia minor (Griscb.) Knobl.

Antioxidant activity-guided fractionations of chloroform extract of Swertia minor yielded five known tetraoxygenated xanthones (1-5), of which compound 3 was isolated for the first time from plant sources. Compounds 1-5 were identified with the aid of extensive NMR spectroscopic studies. A relationship between the structural features of 1-5 and their antioxidant activity was also determined. Among these bioactive isolates (1-5), compound 4 exhibited strong scavenging effect in DPPH (IC(50) = 10.31 µg mL(-1)), FRAP (8536.32 ± 34.1 Mmol Fe (II) g(-1)) and metal chelating (17.2 ± 0.88 mg EDTA g(-1)) assays. Compound 5 was potently active in secondary antioxidant assay (i.e. binding to metal ions strongly); however, its primary antioxidant capacity was found to be feeble.

Synthesis, antioxidant and toxicological study of novel pyrimido quinoline derivatives from 4-hydroxy-3-acyl quinolin-2-one.

A series of novel pyrimido and other fused quinoline derivatives like 4-methyl pyrimido [5,4-c]quinoline-2,5(1H,6H)-dione (4a), 4-methyl-2-thioxo-1,2-dihydropyrimido [5,4-c]quinoline-5(6H)-one (4b), 2-amino-4-methyl-1,2-dihydropyrimido [5,4-c]quinolin-5(6H)-one (4c), 3-methylisoxazolo [4,5-c]quinolin-4(5H)-one (4d), 3-methyl-1H-pyrazolo [4,3-c]quinoline-4(5H)-one (5e), 5-methyl-1H-[1,2,4] triazepino [6,5-c]quinoline-2,6(3H,7H)-dione (5f), 5-methyl-2-thioxo-2,3-dihydro-1H-[1,2,4]triazepino [6,5-c]quinolin-6(7H)-one (5 g) were synthesized regioselectively from 4-hydroxy-3-acyl quinolin-2-one 3. They were screened for their in vitro antioxidant activities against radical scavenging capacity using DPPH(), Trolox equivalent antioxidant capacity (TEAC), total antioxidant activity by FRAP, superoxide radical (O(2)(°-)) scavenging activity, metal chelating activity and nitric oxide scavenging activity. Among the compounds screened, 4c and 5 g exhibited significant antioxidant activities.

A two-photon fluorescent probe for near-membrane calcium ions in live cells and tissues.

A two-photon fluorescent probe (ACaL) is reported that can be excited by 780 nm fs pulses, shows high photostability and negligible toxicity, and can visualize near-membrane Ca2+ in live cells and deep inside live tissues by two-photon microscopy.

3-(1H-Benzimidazol-2-yl)-2-chloro-8-methyl-quinoline.

Two independent mol-ecules of the title compound, C(17)H(12)ClN(3), are present in the structure. The angle between the planes defined by the atoms of the benzimidazole unit and the quinoline unit are 45.2 (3) and 44.0 (3)°, indicating an essentially identical conformation for both mol-ecules. Each of the independent mol-ecules is linked with a symmetry equivalent by an inter-molecular N-H⋯N hydrogen bond involving the two benzimidazole N atoms, to form chains in the crystallographic c direction.

2-{2-[3-(1H-Benzimidazol-2-yl)quinolin-2-yl-oxy]eth-oxy}ethanol.

In the title compound, C(20)H(19)N(3)O(3), the inter-planar angle between the benzimidazole unit and the quinoline unit is 25.1 (2)°. Two different hydrogen bonds involving the hydr-oxy group and the imidazole unit are present. An intra-molecular N-H⋯O hydrogen bond links the hydr-oxy group of the side chain with the imidazole unit, forming a 12-membered ring, and an inter-molecular O-H⋯N hydrogen bond links the mol-ecules, forming chains in the crystallographic b direction.