Sathiah Thennarasu

Resveratrol stabilized gold nanoparticles enable surface loading of doxorubicin and anticancer activity

The green synthesis of gold nanoparticles was achieved by exploiting the antioxidant property of resveratrol (R). The formation of resveratrol stabilized gold nanoparticles (R-GNPs) was confirmed by the observation of the surface plasmon resonance band at 537 nm. The average size of R-GNPs produced in resveratrol medium was ~35nm. The geometrical shape and zeta potential of the gold nanoparticles were spherical and -21.2 mV, respectively. R-GNPs showed excellent stability in saline and other buffers mimicking the physiological pH. The MTT assay using fibroblast cells from explants tissue revealed the biocompatibility of R-GNPs. The cytotoxic activity of doxorubicin loaded R-GNPs against glioma carcinoma cell line (LN 229), showed the suitability of R-GNPs as a carrier for anticancer drugs.

Donor atom selective coordination of Fe3+ and Cr3+ trigger fluorophore specific emission in a rhodamine–naphthalimide dyad

A rhodamine–naphthalimide dyad with multiple coordination sites displays Fe3+ and Cr3+ specific absorption and fluorescence emission profiles and permits specific detection of Fe3+ and Cr3+ ions present in aqueous samples, and live A549 and CHO cells in a chemoselective manner.

Selective interactions of trivalent cations Fe3+, Al3+ and Cr3+ turn on fluorescence in a naphthalimide based single molecular probe

Synthesis and fluorescence turn-on behavior of a naphthalimide based probe is described. Selective interactions of trivalent cations Fe(3+), Al(3+) or Cr(3+) with probe 1 inhibit the PET operating in the probe, and thereby, permit the detection of these trivalent cations present in aqueous samples and live cells. Failure of other trivalent cations (Eu(3+), Gd(3+) and Nb(3+)) to inhibit the PET process in 1 demonstrates the role of chelating ring size vis-à-vis ionic radius in the selective recognition of specific metal ions.

Base catalysed domino and self-domino Michael–Aldol reactions: one-pot synthesis of dispirocyclopentaneoxindoles containing multiple chiral stereocenters

A one-pot method for the construction of three classes of densely functionalized dispirocyclopentaneoxindoles containing multiple chiral stereocenters is developed. Base promoted self-domino and domino reactions with and without the participation of solvent, alcohol, is accomplished. Piperidine catalyzed self-domino reaction involves the participation of the nucleophilic solvent, alcohol, resulting in complex dispiro compounds containing four and five diastereoisomeric centers. Triethylamine promotes the self-domino reaction between two molecules of 3-phenacylideneoxindoles with added nucleophiles, and not with the solvent nucleophile. Diisopropylethylamine facilitates the domino reaction between 3-phenacylidineoxindole and phenacylacenaphthylenone allowing the construction of novel dispirocyclopentaneoxindoles with high yields and diastereoselectivity. A plausible mechanism is tentatively proposed to account for the diastereoselectivity of the domino Michael–Aldol reaction.

Acetic acid promoted tandem cyclization of in situ generated 1,3-dipoles: stereoselective synthesis of dispiroimidazolidinyl and dispiropyrrolidinyl oxindoles with multiple chiral stereocenters

We report acetic acid promoted in situ generation of ketimine and a 1,3-dipole that results in regio- and diastereoselective formation of dispiropyrrolidineoxindoles and dispiroimidazolidineoxindoles via tandem cycloaddition. This novel one-pot reaction generates four chiral centres with two contiguous spirostereocenters in dispiropyrrolidineoxindoles, and three chiral centres with two distal spirostereocenters in dispiroimidazolidineoxindoles.

Synthesis of Novel Pyridopyridazin-3(2H)-one Derivatives and Evaluation of Their Cytotoxic Activity against MCF-7 Cells

A series of pyridopyridazin-3(2H)-one derivatives was synthesized in two facile steps. Mannich-type three-component condensation afforded the 2,6-diaryl piperidin-4-one derivatives, which underwent intramolecular cyclization in the presence of hydrazine or phenylhydrazine to yield the corresponding pyridopyridazin-3(2H)-one derivatives. All the derivatives of pyridopyridazin-3(2H)-one, except 3e and 3f, showed moderate activity against human breast adenocarcinoma (MCF-7) cells. The higher degree of inhibition of MCF-7 cell proliferation shown by 2a–2f indicates the significance of the amide proton in pyridopyridazin-3(2H)-one derivatives.

Ethyl 1''-benzyl-2''-oxo-2',3',5',6',7',7a'-hexa-hydro-1'H-di-spiro-[indeno-[1,2-b]quinoxaline-11,2'-pyrrolizine-3',3''-indoline]-1'-carboxyl-ate monohydrate.

In the title compound, C38H32N4O3·H2O, the quinoxaline–indene and pyrrolizine systems are essentially planar, with maximum deviations from their mean planes of 0.162 and 0.563 Å, respectively. The pyrrolizine ring forms dihedral angles of 88.53 (5) and 89.95 (8)° with the quinoxaline–indene system and the indoline ring, respectively. The central pyrrolidine ring has an envelope conformation with the C atom bearing the quinoxaline-indene system as the flap. The pyrrolidine ring of the indole system adopts an envelope conformation with the C atom bonded to the pyrrolizine ring N atom as the flap. The five-membered ring attached to the central pyrolidine ring adopts a twisted conformation. In the crystal, O—H⋯N and O—H⋯O hydrogen bonds between water molecules and pyrrolizine N and carbonyl O atoms together with C—H⋯O interactions result in chains along [100].

Antiviral activity of Thiosemicarbazones derived from α-amino acids against Dengue virus†

The endemicity and seasonal outbreaks of Dengue disease in most tropical and subtropical countries underscores an urgent need to develop effective prevention and control measures. Development of a Dengue vaccine, which is complicated by the Antibody Dependent Enhancement effect (ADE), a viral inhibitor, seems prudent as it would inhibit the spread of the virus. In vitro methods such as MTT assay and plaque formation unit reduction assays were employed for screening the viral inhibitory property of α‐amino acid based Thiosemicarbazides. The results elicits that at concentrations not exceeding the maximum non cytotoxic concentration (MNCC), these compounds completely prevented Dengue virus infection in vero cells as indicated by the absence of cytopathic effects in a dose‐dependent manner. The high potency of Bz‐Trp‐TSC against all four types of Dengue virus infection elevates Thiosemicarbazide as a lead antiviral agent for Dengue disease. Screening small molecules for antiviral activity against the most rapidly spreading mosquito‐borne viral disease is being explored by several research groups. Our findings would help to augment the efforts to identify the lead compounds for antiviral therapy to combat the Dengue disease. J. Med. Virol. 89:546–552, 2017.

A novel 2-(2′-aminophenyl)benzothiazole derivative displays ESIPT and permits selective detection of Zn2+ ions: experimental and theoretical studies

Synthesis of a novel 2-(2′-aminophenyl)benzothiazole based probe (1) and demonstration of excited state intramolecular proton transfer (ESIPT) with a large Stokes shift (∼246 nm) are presented. Selective interactions of probe 1 with DMSO and Zn2+ result in the inhibition of ESIPT operating in 1. Inhibition of ESIPT by only Zn2+ and not by other common metal ions permits the selective detection of Zn2+ at concentrations as low as 4.5 × 10−9 M in aqueous medium.

Ethyl 1′′-benzyl-1′-methyl-2′′-oxodi­spiro­[indeno­[1,2-b]quinoxaline-11,3′-pyrrolidine-2′,3′′-indoline]-4′-carboxyl­ate

In the title compound, C36H30N4O3, the quinoxaline–indene system is roughly planar, with a maximum deviation from the mean plane of 0.218 Å for the C atom shared with the central pyrrolidine ring. This latter ring forms dihedral angles of 84.54 (7) and 83.91 (8)° with the quinoxaline–indene system and the indole ring, respectively. The central pyrrolidine ring has an envelope conformation with the N atom as the flap, while the pyrrolidine and five-membered rings of the indole group adopt twisted conformation and envelope (with the C atom bearing the quinoxaline–indene system as the flap) conformations, respectively. In the crystal, molecules are linked via weak C—H⋯N hydrogen bonds, forming a chain running along [100].