Highly selective synthesis of the ring-B reduced chlorins by ferric chloride-mediated oxidation of bacteriochlorins: effects of the fused imide vs isocyclic ring on photophysical and electrochemical properties

The oxidation of bacteriopyropheophorbide with ferric chloride hexahydrate or its anhydrous form produced the ring-D oxidized (ring-B reduced) chlorin in >95% yield. Replacing the five-member isocyclic ring in bacteriopyropheophorbide- a with a fused six-member N-butylimide ring system made no difference in regioselective oxidation, and the corresponding ring-B reduced chlorin was isolated in almost quantitative yield. When the oxidant was replaced by 2,3-dichloro-5,6-dicyano-p-benzoquinone, which is frequently used at the oxidizing stage of the porphyrin synthesis, the ring-B oxidized (ring-D reduced) chlorins were obtained. With both ring-B reduced and ring-D reduced chlorins in hand, their photophysical and electrochemical properties were examined and compared for the first time. The ring-B reduced chlorine 20, with a fused six-member N-butylimide ring, exhibits the most red-shifted absorption band (at lambda(max) = 746 nm), the lowest fluorescence quantum yield (4.5%), and the largest quantum yield of singlet oxygen formation (67%) among the reduced ring-B and ring-D chlorins investigated in this study. Measurements of the one-electron oxidation and reduction potentials show that compound 20 is also the easiest to oxidize among the examined compounds and the third easiest to reduce. In addition, the 1.62 eV HOMO-LUMO gap of 20 is the smallest of the examined compounds, and this agrees with values calculated using the DFT method. Spectroelectrochemical measurements afforded UV-visible absorption spectra for both the radical cations and radical anions of the examined chlorins. The ring-B reduced compound 20, with a fused six-member N-butylimide ring, is regarded as the most promising candidate in this study for photodynamic therapy because it has the longest wavelength absorption and the largest quantum yield of singlet oxygen formation among the compounds investigated.     

Water deficit stress mitigation by calcium chloride in Catharanthus roseus: effects on oxidative stress, proline metabolism and indole alkaloid accumulation

The present investigation was conducted to determine whether CaCl(2) increases Catharanthus roseus drought tolerance and if such tolerance is correlated with changes in oxidative stress, osmoregulation and indole alkaloid accumulation. C. roseus plants were grown under water deficit environments with or without CaCl(2). Drought induced oxidative stress was measured in terms of lipid peroxidation (LPO) and H(2)O(2) contents, osmolyte concentration, proline (PRO) metabolizing enzymes and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with 5mM CaCl(2) and 5mM CaCl(2) alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stressed plants showed increased LPO, H(2)O(2), glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) activity and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. Addition of CaCl(2) to drought stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the gamma-GK activities. Calcium ions increased the GB contents. CaCl(2) appears to confer greater osmoprotection by the additive role with drought in GB accumulation. The drought with CaCl(2)-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to drought stressed and well-watered plants.     

Changes in antioxidant metabolism of Vigna unguiculata (L.) Walp. by propiconazole under water deficit stress

In the present study, a pot culture experiment was conducted to estimate the ameliorating effect of propiconazole (PCZ) on drought stress in cowpea (Vigna unguiculata (L.) Walp.) plants. From 30 days after sowing (DAS), the plants were subjected to 3, 6 and 9 days interval drought (DID) stress and drought stress with PCZ at 15 and 15 mg l(-1) PCZ alone and 1 day interval irrigation was kept as control. The plant samples were collected on 34 DAS (3 DID), 37 DAS (6 DID) and 40 DAS (9 DID). The plants were separated into root, stem and leaf for estimating the antioxidant contents and activities of antioxidant enzymes. Individual and combined drought stress and PCZ treatments increased ascorbic acid (AA), alpha-tocopherol (alpha-toc) contents, superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and polyphenol oxidase (PPO) activities when compared to control. The PCZ treatment mitigated the adverse effects of drought stress by increasing the antioxidant potentials and thereby paved the way for overcoming drought stress in V. unguiculata plants.     

Remarkable regioselective position-10 bromination of bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a

Both bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a on reacting with NBS (N-bromosuccinamide) undergo electrophilic bromination to provide 10-bromo analogs. The electronic nature of the substituents present at position-3 did not make any difference in the regioselective outcome of the brominated products. These relatively stable brominated chlorins and bacteriochlorins provide an easy way of introducing a wide variety of functionalities, which could be extremely useful in developing improved agents for biomedical applications and supramolecular chemistry.     

Synthesis of cubic Li<Subscript>7</Subscript>La<Subscript>3</Subscript>Zr<Subscript>2</Subscript>O<Subscript>12</Subscript> by modified sol–gel process

Polycrystalline cubic Li₇La₃Zr₂O₁₂ (LLZ) with garnet-related type structure has been synthesized at 700 °C by modified sol–gel processes using citric acid as organic complexing agent and butan-1-ol or propan-2-ol as surface active agent. Thermal analysis (thermogravimetric/differential thermal analysis) indicated that the gel must be annealed at around 700 °C to completely remove the organic solvent. X-ray powder diffraction, X-ray fluorescence, and scanning electron microscopic investigations revealed that Al may not be essential to form cubic-phase LLZ; however, the addition of Al₂O₃ led to enhanced sintering of LLZ.     

A Novel Dialkylamino-Functionalized Chalcone,DML6, Inhibits Cervical Cancer Cell Proliferation,In Vitro,via Induction of Oxidative Stress,Intrinsic Apoptosis and Mitotic Catastrophe

In this study, we designed, synthesized and evaluated, in vitro, novel chalcone analogs containing dialkylamino pharmacophores in the cervical cancer cell line, OV2008. The compound, DML6 was selective and significantly decreased the proliferation of OV2008 and HeLa cells in sub-micromolar concentrations, compared to prostate, lung, colon, breast or human embryonic kidney cell line (HEK293). DML6, at 5 μM, arrested the OV2008 cells in the G2 phase. Furthermore, DML6, at 5 μM, increased the levels of reactive oxygen species and induced a collapse in the mitochondrial membrane potential, compared to OV2008 cells incubated with a vehicle. DML6, at 5 μM, induced intrinsic apoptosis by significantly (1) increasing the levels of the pro-apoptotic proteins, Bak and Bax, and (2) decreasing the levels of l the anti-apoptotic protein, Bcl-2, compared to cell incubated with a vehicle. Furthermore, DML6, at 5 and 20 μM, induced the cleavage of caspase-9, followed by subsequent cleavage of the executioner caspases, caspase-3 and caspase-7, which produced OV2008 cell death. Overall, our data suggest that DML6 is an apoptosis-inducing compound that should undergo further evaluation as a potential treatment for cervical cancer.     

Robust stability analysis for Markovian jumping interval neural networks with discrete and distributed time-varying delays

This paper investigates robust stability analysis for Markovian jumping interval neural networks with discrete and distributed time-varying delays. The parameter uncertainties are assumed to be bounded in given compact sets. The delay is assumed to be time-varying and belong to a given interval, which means that the lower and upper bounds of interval time-varying delays are available. Based on the new Lyapunov–Krasovskii functional (LKF), some inequality techniques and stochastic stability theory, new delay-dependent stability criteria have been obtained in terms of linear matrix inequalities (LMIs). Finally, two numerical examples are given to illustrate the less conservative and effectiveness of our theoretical results.     

Pressure-induced colossal piezoresistance effect and the collapse of the polaronic state in the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn2O7

We have investigated the effect of hydrostatic pressure as a function of temperature on the resistivity of a single crystal of the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7). Whereas a strong insulating behaviour is observed at all temperatures at ambient pressure, a clear transition into a metallic-like behaviour is induced when the sample is subjected to a pressure (P) of ~1.0 GPa at T < 70 K. A huge negative piezoresistance ~10(6) in the low temperature region at moderate pressures is observed. When the pressure is increased further (5.5 GPa), the high temperature polaronic state disappears and a metallic behaviour is observed. The insulator to metal transition temperature exponentially increases with pressure and the distinct peak in the resistivity that is observed at 1.0 GPa almost vanishes for P > 7.0 GPa. A modification in the orbital occupation of the e(g) electron between 3d(x(2)-y(2)) and 3d(z(2)-r(2)) states, as proposed earlier, leading to a ferromagnetic double-exchange phenomenon, can qualitatively account for our data.     

Growth,structural, thermal,optical, dielectric,mechanical and laser damage threshold studies of nicotinium tartrate single crystals

An organic nonlinear optical nicotinium tartrate (NT) single crystal was grown by slow evaporation solution growth technique. The cell parameters of NT crystal were confirmed by single crystal and powder X-ray diffraction studies. The crystalline perfection of NT crystal was examined from HRXRD studies. The presence of functional groups was identified from FTIR spectral analysis. TGA and DSC studies revealed the thermal stability of NT crystal. UV–vis-NIR spectral studies showed that the NT crystal has wide transmission window in the entire visible region. The dielectric study on NT crystal established the normal dielectric behavior. The mechanical strength of NT crystal was studied by Vickers’ microhardness test. The laser damage threshold value of NT crystal was measured using Nd:YAG laser. The relative SHG efficiency of NT was measured to be 1.1 times that of KDP.