Identification and characterization of in vitro and in vivo fidarestat metabolites: Toxicity and efficacy evaluation of metabolites

The progression of diabetic complications can be prevented by inhibition of aldose reductase and fidarestat considered to be highly potent. To date, metabolites of the fidarestat, toxicity, and efficacy are unknown. Therefore, the present study on characterization of hitherto unknown in vitro and in vivo metabolites of fidarestat using liquid chromatography–electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) is undertaken. In vitro and in vivo metabolites of fidarestat have been identified and characterized by using LC/ESI/MS/MS and accurate mass measurements. To identify in vivo metabolites, plasma, urine, and feces samples were collected after oral administration of fidarestat to Sprague–Dawley rats, whereas for in vitro metabolites, fidarestat was incubated in human S9 fraction, human liver microsomes, and rat liver microsomes. Furthermore, in silico toxicity and efficacy of the identified metabolites were evaluated. Eighteen metabolites have been identified. The main in vitro phase I metabolites of fidarestat are oxidative deamination, oxidative deamination and hydroxylation, reductive defluroniation, and trihydroxylation. Phase II metabolites are methylation, acetylation, glycosylation, cysteamination, and glucuronidation. Docking studies suggest that oxidative deaminated metabolite has better docking energy and conformation that keeps consensus with fidarestat whereas the rest of the metabolites do not give satisfactory results. Aldose reductase activity has been determined for oxidative deaminated metabolite (F‐1), and it shows an IC50 value of 0.44 μM. The major metabolite, oxidative deaminated, did not show any cytotoxicity in H9C2, HEK, HEPG2, and Panc1 cell lines. However, in silico toxicity, the predication result showed toxicity in skin irritation and ocular irritancy SEV/MOD versus MLD/NON (v5.1) model for fidarestat and its all metabolites. In drug discovery and development research, it is distinctly the case that the potential for pharmacologically active metabolites must be considered. Thus, the active metabolites of fidarestat may have an advantage as drug candidates as many drugs were initially observed as metabolites.     

A theoretical charge density study on nitrogen-rich 4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole (TNBI) energetic molecule

The bond topological and electrostatic properties of nitrogen-rich 4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole (TNBI) energetic molecule have been calculated from the DFT method with the basis set 6-311G** and the AIM theory. The optimized geometry of this molecule is almost matched with the experimental geometric parameters. The electron density at the bond critical point and the Laplacian of electron density of C–NO₂ bonds are not equal, one of them is much weaker than the other. Similar trend exists in the C–N bonds of the imidazole ring of the molecule. The ratio of the bond dissociation energy (BDE) of the weakest bond to the molecular total energy exhibits nearly a linear correlation with the impact sensitivity; its h ₅₀% value is ~32.01 cm. The electrostatic potential around both the nitro groups are found unequal; the NO₂ group of weakest C–NO₂ bond exhibits an extended electronegative region.     

Multicolored and white-light phosphors based on doped GdF3 nanoparticles and their potential bio-applications

Rare-earth-doped gadolinium fluoride nanocrystals were synthesized by a single step synthesis employing ethylene glycol as solvent. Based on X-ray diffraction studies, stabilization of hexagonal modification of GdF(3) has been inferred. The microscopic studies show formation of uniformly distributed nanocrystals (~15 nm). The nanoparticles are readily dispersible in water and show bright luminescence in colloidal solution. The luminescence properties have been investigated as a function of activator concentrations, and enhanced optical properties have been attributed to efficient energy transfer from the Gd(3+) to the activator RE(3+) ions, which has further been confirmed by steady-state and time-resolved optical studies. It has been demonstrated that on doping appropriate amount of activators in host GdF(3), a novel white-light-emitting phosphor is obtained with CIE co-ordinates and correlated color temperature (CCT) very close to broad daylight. This can have promising applications as phosphor for white-light ultraviolet-light-emitting diodes (UV-LEDs). Our experiments showed efficient labeling of human breast carcinoma cells (MCF-7) by Tb(3+)-doped GdF(3) nanoparticles. The fluorescence intensity was found to be dependent on the surface modifying/coating agent, and the results were validated using confocal microscopy in terms of localization of these functionalized nanoparticles.     

Biohydrogen Production from Cheese Whey Wastewater in a Two-Step Anaerobic Process

Cheese whey-based biohydrogen production was seen in batch experiments via dark fermentation by free and immobilized Enterobacter aerogenes MTCC 2822 followed by photofermentation of VFAs (mainly acetic and butyric acid) in the spent medium by Rhodopseudomonas BHU 01 strain. E. aerogenes free cells grown on cheese whey diluted to 10 g lactose/L, had maximum lactose consumption (～79%), high production of acetic acid (1,900 mg/L), butyric acid (537.2 mg/L) and H(2) yield (2.04 mol/mol lactose; rate,1.09 mmol/L/h). The immobilized cells improved lactose consumption (84%), production of acetic acid (2,100 mg/L), butyric acid (718 mg/L) and also H(2) yield (3.50 mol/mol lactose; rate, 1.91 mmol/L/h). E. aerogenes spent medium (10 g lactose/L) when subjected to photofermentation by free Rhodopseudomonas BHU 01 cells, the H(2) yield reached 1.63 mol/mol acetic acid (rate, 0.49 mmol/L/h). By contrast, immobilized Rhodopseudomonas cells improved H(2) yield to 2.69 mol/mol acetic acid (rate, 1.87 mmol/L/h). The cumulative H(2) yield for free and immobilized bacterial cells was 3.40 and 5.88 mol/mol lactose, respectively. Bacterial cells entrapped in alginate, had a sluggish start of H(2) production but outperformed the free cells subsequently. Also, the concomitant COD reduction for free cells (29.5%) could be raised to 36.08% by immobilized cells. The data suggest that two-step fermentative H(2) production from cheese whey involving immobilized bacterial cells, offers greater substrate to- hydrogen conversion efficiency, and the effective removal of organic load from the wastewater in the long-term.     

Self‐association and hydrogen bonding of propionaldehyde in binary mixtures with water and methanol investigated by concentration‐dependent polarized Raman study and DFT calculations

The Raman spectra of neat propionaldehyde [CH₃CH₂CHO or propanal (Pr)] and its binary mixtures with hydrogen‐donor solvents, water (W) and methanol (M), [CH₃CH₂CHO + H₂O] and CH₃CH₂CHO + CH₃OH] with different mole fractions of the reference system, Pr varying from 0.1 to 0.9 at a regular interval of 0.1, were recorded in the ν(CO) stretching region, 1600–1800 cm⁻¹. The isotropic parts of the Raman spectra were analyzed for both the cases. The wavenumber positions and line widths of the component bands were determined by a rigorous line‐shape analysis, and the peaks corresponding to self‐associated and hydrogen‐bonded species were identified. Raman peak at ∼1721 cm⁻¹ in neat Pr, which has been attributed to the self‐associated species, downshifts slightly (∼1 cm⁻¹) in going from mole fraction 0.9 to 0.6 in (Pr + W) binary mixture, but on further dilution it shows a sudden downshift of ∼7 cm⁻¹. This has been attributed to the low solubility of Pr in W (∼30%), which does not permit a hydrogen‐bonded network to form at higher concentrations of Pr. A significant decrease in the intensity of this peak in the Raman spectra of Pr in a nonpolar solvent, n‐heptane, at high dilution (C = 0.05) further confirms that this peak corresponds to the self‐associated species. In case of the (Pr + M) binary mixture, however, the spectral changes with concentration show a rather regular trend and no special features were observed. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydrogen bonding in different pyrimidine–methanol clusters probed by polarized Raman spectroscopy and DFT calculations

We report on the hydrogen bonding between pyrimidine (Pd) and methanol (M) as H‐donor in this study. Hydrogen bonds between pyrimidine and methanol molecules as well as those between different methanol molecules significantly influence the spectral features at high dilution. The ring‐breathing mode ν₁ of the reference system Pd was chosen as a marker band to probe the degree of hydrogen bonding. Polarized Raman spectra in the region 970–1020 cm⁻¹ for binary mixtures of (pyrimidine + methanol) at 28 different mole fractions were recorded. A Raman line shape analysis of the isotropic Raman line profiles at all concentrations revealed three distinct spectral components at mole fractions of Pd below 0.75. The three components are attributed to three distinct groups of species: ‘free Pd’ (pd), ‘Pd with low methanol content’ (pd1) and ‘Pd with high‐methanol content’ (pd2). The two latter species differ considerably in the pattern and the strengths of the hydrogen bonds. The results of density functional theory calculations on structures and vibrational spectra of neat Pd and eight Pd/M complexes with varying methanol content support our interpretations of the experimental results. A nice spectra–structure correlation for the different cluster subgroups was obtained, similar to earlier results obtained for Pd and water. Apart from N···H and O···H hydrogen bonds between pyrimidine and methanol, O···H hydrogen bonds formed among the methanol molecules in the cluster at high methanol content also play a crucial role in the interpretation of the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

Dissolutive Capillary Penetration with Expanding Pores and Transient Contact Angles

The penetration kinetics of a cylindrical capillary and a capillary porous body with a temporally expanding capillary radius due to reactive dissolution ahead of the liquid front is modeled under conditions where the equilibrium contact angle is not attained during at least part of the penetration process. These effects cause deviations from the predictions of the Washburn equation, with the actual penetration kinetics depending upon the rate processes involved. Copyright 2000 Academic Press.     

Fast separation and sensitive detection of carcinogenic aromatic amines by reversed-phase micro-liquid chromatography coupled with electrochemical detection

A micro-LC method was developed for the fast and sensitive analysis of aromatic amines by electrochemical detection. The chromatographic separation of nine carcinogenic aromatic amines was performed on an ABZ + PLUS column with detection limits up to pM L(-1) levels. Mobile phase comprised of methanol-acetate buffer of pH 5 (45:55, v/v) used at a flow rate of 0.2 ml min(-1). The detection was performed with a 6 mm glassy carbon electrode at an applied potential of 0.8 V versus Ag/AgCl. An intraday RSD for retention time and peak area were between 0.22% and 0.73% and 1.86% and 4.03%, respectively. The interdays RSD for retention time and peak area were between 0.47% and 1.35% and 2.04% and 4.42%, respectively. The applicability of the assay has been demonstrated by analyzing these aromatic amines in lake water and synthetic food colour additives. A comparison is given between electrochemical and UV detection.     

Amperometric determination of thorium as selenite

Summary Amperometric titration of thorium as selenite in a base electrolyte consisting of 0.9 M ammonium acetate in 60–70 per cent alcohol (ph 6.2–6.4) has been described. The titration is carried out at –1.0 V vs. S.C.E. A reversed L-type of curve is obtained and the formation of a normal selenite is suggested. The accuracy of the procedure is comparable with that obtained with other classical methods.

---

Zusammenfassung Es wird ein Verfahren zur amperometrischen Titration von Thorium mit Selenitlösung beschrieben. Die Titration wird bei –1,0 V (gegen die ges. Kalomelelektrode) ausgeführt, bei Gegenwart von 0,9 m Ammoniumacetat und 60–70% Alkohol (pH 6,2–6,4). Man erhält eine Titrationskurve, die etwa die Form eines umgekehrten L hat. Die Genauigkeit des Verfahrens ist vergleichbar mit der anderer klassischer Methoden. Es wird angenommen, daß die Reaktion zur Bildung eines normalen Selenits führt.

     

Peroxidative catalytic oxidation of alcohols catalyzed by heterobinuclear vanadium(V) complexes using H2O2 as terminal oxidizing agents

Here we report the catalytic oxidation of benzylic alcohol, hetero‐aryl alcohols and propargylic alcohols to their corresponding carbonyl compound using heterobimetallic sodium‐dioxidovanadium(V) complexes. The present catalytic oxidation studies proceed at 70 °C using H₂O₂ as terminal oxidant. During the whole process, the complexes react with hydrogen peroxide to form peroxo‐vanadium(V) species. The present study shows the heterogeneity of pre‐catalyst which could be easily recovered and moreover isolation of product is very simple.