Pratibha Sharma

Exploration of antimicrobial and antioxidant potential of newly synthesized 2,3-disubstituted quinazoline-4(3H)-ones

A series of 2-(chloromethyl)-3-(4-methyl-6-oxo-5-[(E)-phenyldiazenyl]-2-thioxo-5,6-dihydropyrimidine-1(2H)-yl)quinazoline-4(3H)-ones 9a-j was synthesized by treating 2-(chloroacetyl)amino benzoic acid with 3-amino-6-methyl-5-[(E)-phenyldiazenyl]-2-thioxo-2,5-dihydropyrimidine-4(3H)-one 8a-j and was screened for in vitro antibacterial activities against a representative panel of Gram-positive and Gram-negative bacteria. The compounds were synthesized in excellent yields and the structures were corroborated on the basis of IR, (1)H NMR, Mass and elemental analysis data. All the synthesized compounds elicited the potent inhibitory action against all the tested bacterial stains. Furthermore, in order to explore the antioxidant potential of newly synthesized compounds, the free radical scavenging activity measurement were performed by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay method. It is revealed from the antioxidant screening results that the compounds 9c and f manifested profound antioxidant potential.

Reconfiguration strategy for optimization of solar photovoltaic array under non-uniform illumination conditions

Performance of a solar photovoltaic (SPV) array is affected by variations in temperature, solar insolation and array configuration. At times, the SPV arrays are susceptible to non-uniform illumination due to shading caused by passing cloud, towers, trees etc. The effect of partial shading is critical; it can cause problems such as irregular P-V characteristics (multiple peaks) which makes power optimization difficult by the conventional power extraction techniques and results in significant loss of power. In most SPV systems, a DC-DC converter is connected at the SPV output to compensate for the drop in the PV output voltage. Under shaded conditions, a high gain DC-DC converter is needed to boost the low SPV voltage, which leads to additional power loss. Under such conditions, an appropriate reconfiguration scheme may prove to be beneficial as it ensures a certain minimum voltage for the next stage, obviating the need for high voltage gain, thereby reducing the power losses in the DC-DC converter. Under non-uniform illumination conditions, the P-V characteristics may exhibit multiple peaks. In the absence of reconfiguration, the conventional power optimization technique will get trapped at the local maxima and result in loss of power. While reconfiguration shows advantage in power as well as makes the P-V characteristics less irregular making the convergence to the maximum power point easier. This paper proposes a reconfiguration strategy which ensures a certain minimum deviation from the operating voltage with improvement in power. A reconfigurable 4×4 solar PV cell array is designed. The experimental results for a 4×4 cell array demonstrating the reconfiguration strategy showing improvement in power has been included. And simulation results of reconfiguration of flexible PV modules under non-uniform conditions are also provided.

Exploration of in vitro time point quantitative evaluation of newly synthesized benzimidazole and benzothiazole derivatives as potential antibacterial agents

Present communication deals with the in vitro time point quantitative antibacterial evaluation of newly synthesized 1,2-disubstituted benzimidazoles (3a-p) and 2-substituted benzothiazoles (5a-h) against Gram-positive bacteria Staphylococcus aureus, Bacillus cereus, and Gram-negative bacteria Vibrio cholerae, Shigella dysenteriae and Escherichia coli. These compounds were synthesized under mild reaction conditions using Al(2)O(3)-Fe(2)O(3) nanocrystals as heterogeneous catalyst. Bio-evaluation studies revealed that, compounds 3a, 5a and 5d exhibited moderate to good antibacterial activity against all the tested bacterial stains. The compounds 3a, 3f and 5a have shown enhanced inhibitory activity compared with standard antibacterial drug ciprofloxacin against V. cholerae, B. cereus, and S. dysenteriae, respectively. Additionally, the compounds 3a, 3e, 3f, 3h and 5b displayed complete bactericidal activity within 24 h, whereas ciprofloxacin took 48 h to kill those bacteria completely.

Cardioprotective potential of N,α-L-rhamnopyranosyl vincosamide, an indole alkaloid, isolated from the leaves of Moringa oleifera in isoproterenol induced cardiotoxic rats: in vivo and in vitro studies.

Hitherto unknown protective effect of N,α-L-rhamnopyranosyl vincosamide (VR), isolated from Moringa oleifera leaves in isoproterenol (ISO)-induced cardiac toxicity was evaluated in rats. Oral administration of VR at 40 mg/kg for 7 days markedly reduced the ISO-induced increase in the levels of serum cardiac markers such as troponin-T, creatine kinase-MB, lactate dehydrogenase and glutamate pyruvate transaminase as well as cardiac lipid peroxidation with a parallel increase in the cellular antioxidants suggesting its cardio-protective and free radical scavenging potential, which was latter confirmed by in vitro study. Rats treated with test compound also improved the ISO-induced abnormal changes in ECG as well as in cardiac histology. A reduction in myocardial necrosis was further evidenced by the tri-phenyl tetrazolium chloride (TTC) stain in isolated test drug pretreated rats. These findings suggest the cardio-protective potential of the isolated alkaloid and possibly the beneficial action is mediated through its free radical scavenging property.

QSAR modeling of synthesized 3-(1,3-benzothiazol-2-yl) 2-phenyl quinazolin-4(3H)-ones as potent antibacterial agents

Present communication elicits the designing and synthesis of 3-(1,3-benzothiazol-2-yl) 2-phenyl quinazolin-4(3H)-ones as potential antibacterial agents. A number of substituted 2-amino benzothiazoles, 2-amino-5-[(E)-phenyl diazenyl] benzoic acid, and 2-phenyl-4H benzo[d] [1,3] oxazin-4-one were synthesized as the precursor substrates. The compounds were synthesized in excellent yields and the structures were corroborated on the basis of IR, 1H NMR, Mass, and elemental analysis data. These compounds were screened in vitro for their antibacterial activity against a representative panel of Gram positive and Gram negative bacteria and models were generated through quantitative structure–activity relationship (QSAR).The activity contributions due to structural and substituent effects were determined using sequential regression procedure. The antimicrobial assay data show that the synthesized compounds are found to manifest profound antimicrobial activity.

Dynamic power optimization of contoured flexible PV array under Non-Uniform Illumination conditions

Lightweight, flexible PV (FPV) modules are suitable for BIPV and stand-alone applications where contoured layouts are required and system weight is a constraint. This report focuses on optimization of a contoured FPV array which operates under Non Uniform Illumination (NUI) conditions. NUI conditions can occur at low solar angle for contoured layouts and also due to unexpected partial shading events. The output Power Voltage (P-V) characteristics under contouring and partial shading demonstrate severe oscillatory behavior around the maximum power region, which results in inefficient implementation of established tracking algorithms that seek to detect a dominant global maxima. An algorithm for MPP tracking has been proposed that takes into account both static and dynamic parameters. An integrated test system has been developed which can accurately monitor solar irradiance (range 100–1000 Watts/m2) and solar angle and load dependent instantaneous output voltage and current. The system has been designed for maximum current and voltage rating of 3A and 25V respectively. While an output power penalty results due to contouring, our results show a very small energy differential up to a maximum array contour value of 10°. This analysis may lead to development of novel, flexible PV array based designs.

Synthesis and bio-evaluation of aryl hydrazono esters for oviposition responses in Aedes albopictus

A novel series of aryl hydrazono esters (AHE) (1-13) were synthesized (yield 76-98%) to study the oviposition responses in Aedes albopictus (Skuse) mosquitoes for the first time. At a concentration of 10μgml(-1) in dual choice experiment, among the screened compounds, AHE-12 showed remarkable oviposition attractant activity with an oviposition activity index (OAI) of +0.299 (greater than 95% confidence limit) comparable to p-cresol (OAI +0.320) which is well-reported oviposition attractant for Aedes aegypti. Conversely, AHE-10 exhibited highest oviposition deterrent activity with OAI -0.247. The possible utilization of these compounds will be in integrated vector management strategies.

Hydrogen in FeTi thin films by ERDA with Ag107 ions

Abstract Hydrogen content in hydride at various depths is very important. In the present work hydrogen content in hydrogenated FeTi thin films has been investigated by ERDA (Elastic Recoil Detection Analysis) using 160 MeV, Ag 107 ions. ERDA investigations have shown that FeTi thin films without exposing hydrogen have about 50 atm% of hydrogen content and after hydrogenation these films acquire 5–10 atm% of additional hydrogen. It was observed that the hydrogenation of irradiated films did not increase the hydrogen concentration further. It implies than a beam did not cause track formation in the sample at this energy.

Titania nanomaterials: efficient and recyclable heterogeneous catalysts for the solvent-free synthesis of poly-substituted quinolines via Friedlander hetero-annulation

The present communication describes the use of titania (TiO2) nanomaterials of different sizes (16 nm, 35 nm, 70 nm, 200 nm, and 1000 nm) as heterogeneous catalysts for the preparation of a series of medicinally significant poly-substituted quinoline derivatives via Friedlander hetero-annulation. These TiO2 nanomaterials exhibited remarkable catalytic activity with a high substrate to catalyst molar ratio (20 : 1) to achieve the synthetic targets in excellent yields ranging from 81–94%. The effect of catalyst particle size on the yield of the quinolines was also investigated. Yields of product were found to decrease when the TiO2 particle size increased from 16 nm to 1000 nm. GC-MS data indicated that TiO2 nanoparticles having 16 nm and 35 nm size of anatase phase provided better yields of the target compound, followed by particles of 70 nm in size, whereas 200 nm and 1000 nm size of anatase phase did not show the formation of the product under the same reaction conditions. The use of catalyst in solvent-free reaction conditions and its reusability up to five-cycles with similar catalytic response are the unique features of this heterogeneous catalysis. Furthermore, greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yield are the noteworthy features of this eco-friendly green protocol.

Theoretical Evaluation of Global and Local Electrophilicity Patterns to Characterize Hetero-Diels-Alder Cycloaddition of Three-Membered 2H-Azirine Ring System

Present communication elicits an interesting interaction between 2H-azirine and a number of electron rich and electron deficient dienes. A series of substituted 2H-azirine 1-10, and three dienes namely cyclopentadiene D-1, furfural D-2, and dinitrofuran D-3 were chosen to investigate and critically review the reactivity and selectivity of Diels-Alder cycloaddition strategy. The global and local electrophilicity patterns have been evaluated to interpret the electrophilic/nucleophilic behavior of dienes D-1 to D-3 and dienophiles 1-10, in polar Diels-Alder cycloaddition, using the DFT method at the B3LYP/6-31G* level of theory. Regional nucleophilicity have been evaluated using local nucleophilicity descriptor N(k) (Perez, P.; Domingo, L. R.; Duque-Norena, M.; Chamorro, E. J. Mol. Struct. THEOCHEM 2009, 895, 86-91), and regional electrophilicity at the active sites of the interactive species involved in Diels-Alder processes have been described on a quantitative basis using local electrophilicity index omega(k).