Rapid and cost-effective LC–MS/MS method for determination of hydroxycitric acid in plasma: Application in the determination of pharmacokinetics in commercial Garcinia preparations

Garcinia cambogia is one of the most commonly used anti-obesity dietary supplements, and hydroxycitric acid (HCA) is a major constituent in the commercial preparations of Garcinia. High doses of HCA are often consumed without much awareness of its pharmacokinetic and toxicokinetic parameters, and therefore, a complete understanding of its effects is lacking. The first step in understanding these parameters is the availability of a reliable bioanalytical method. Here, we present the first report on a UPLC–MS/MS method for analysis of HCA in rat plasma after a simplified and cost-effective protein precipitation. Chromatographic separation of the analytes in the supernatant was achieved using hydrophilic interaction liquid chromatography, where mass parameters were optimized and a rapid 5-min quantitative assay was developed. The method was highly sensitive, accurate, precise and linear in the concentration range of 10.5–5000 ng/mL (validated according to the United States Food and Drug Administration guidelines). Further, the method was successfully used to describe the pharmacokinetic profile of HCA in rat plasma after the administration of pure HCA and commercial Garcinia preparations.     

Luminescent amphiphilic nanogels by terpyridine-Zn(II) complexation of polymeric micelles

In this work, we investigated terpyridine (tpy)/Zn(II) complexation for the crosslinking of polymeric micelles of the branched poly(ethylene oxide)–poly(propylene oxide) block copolymer Tetronic® 1107 (T1107) in water and produce physically stable amphiphilic luminescent nanogels. Nanoparticles displayed a size of 235 ± 25 and 318 ± 57 nm before and after Zn(II) crosslinking, respectively, as measured by dynamic light scattering. High-resolution scanning electron microscopy analysis revealed the multimicellar nature of the crosslinked nanoparticles. In addition, Zn(II) complexation prevented nanoparticle disassembly after extreme dilution below the critical micellar concentration and reduced the minimum concentration required for the reverse thermal gelation of concentrated aqueous T1107 systems. The cell compatibility and uptake were initially assessed in the murine macrophage cell line RAW 264.7. Results showed that complexation increases the cell compatibility of the nanoparticles with respect to the non-complexed counterparts. In addition, non-crosslinked nanoparticles accumulated in the cell membrane, while the complexed ones were internalized, as observed by confocal laser scanning fluorescence microscopy. Then, the antiproliferative activity of the crosslinked nanoparticles was confirmed in the rhabdomyosarcoma cell line Rh30; their inhibitory concentration 50 (IC₅₀) being 101 μg/mL (6.7 μM). Finally, the encapsulation and release of the hydrophobic antiretroviral efavirenz was characterized in vitro. Complexation slightly reduced the release kinetics with respect to the pristine nanoparticles. Overall results demonstrate the promise of this simple modification strategy to produce amphiphilic nanogels with a set of advantageous physicochemical, optical, and biological properties.     

On Free Fall of a Particle into a Black Hole and Falling Below the Event Horizon in Kramer’s Metric in the Presence of Dark Energy

Russian Physics Journal - For a model of decaying dark energy with a fermion (τ-lepton), additional corrections to the classical estimate of the time of falling of particles into a static...     

A Molibdenum(VI)–Gallein–Diphenhydramine Ion Associate and Its Application to the Extraction-Photometric Determination of Diphenhydramine

Optimum conditions for the formation and extraction of a slightly soluble ion associate of diphenhydramine with the anionic complex molibydenum–gallein were determined. The ternary complex was extracted with butanol at pH 4–7. In the presence of diphenhydramine, the color strength became stronger, which was manifested in the absorption spectra as hypsochromic and bathochromic shifts. Some physicochemical characteristics of the complex were determined, the specificity of the reaction with respect to diphenhydramine was studied, and the probable complexation scheme was proposed. It was found that the molybdenum–gallein–diphenhydramine complex forms at a component ratio of 1: 2: 2. A procedure for the extraction–photometric determination of diphenhydramine in injection solutions and tablets was developed (RSD = 15–20%). The linearity range of the calibration graph was 0.02–0.20 mg/mL.     

Chemical shifts in ESCA and NMR

A detailed examination of the relationship between chemical shifts in ESCA and NMR is presented. It is demonstrated that even in series of closely related compounds a linear correlation between ESCA and NMR shifts cannot be expected. Included is a discussion of reorganization effects on electron binding energies. The close relation between chemical shifts of ESCA and NMR and the spin—rotation constants of molecules is pointed out.     

Numerical studies on the anderson localization problem

Our study of Anderson's tight binding model for strongly disordered electronic systems is extended to a numerical treatment of thed c-conductivity atT=0. For 100 × 100 square lattices, 129 × 129 triangular lattices, and for diamond lattices with 27,000 sites, the behaviour of is studied as a function of the Fermi energy and the disorder. The calculations are based on the exact eigenfunction representation of the Kubo formula, which is evaluated by the systematic application of recursion algorithms. Our results are in favour of Mott's original suggestion of a minimum metallic conductivity _min, both in two and three dimensions. In two dimensions we find the universal value of _min=(0.11 ±0.02)e ²/. Based on the thesis of J. Stein, Regensburg 1979     

Magnetic circular dichroism in the luminescence ofF andF A centres in alkali halides

Summary The magnetic circular dichroism has been in the past an excellent tool to clarify the optical cycle of theF centres in alkali halides and the nature of the relaxed excited state. We have used such technique to study the weak doubleF emission found recently in NaI and the luminescence ofF andF _A centres (of both type I and II) in KCl. We have found that the long-wavelengthF emission in NaI and theF _A (I) emission in KCl∶Na⁺ behave like the well-known emission of theF centres, confirming the attribution of the above luminescence in NaI to the normal relaxed excited state. A completely different behaviour is displayed by the short-wavelengthF emission in NaI and by theF _A (II) emission in KCl∶Li⁺. The experimental data have been compared with the Ham and Grevsmuhl vibronic theory of the relaxed excited state.

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Riassunto Gli effetti di dicroismo magnetico circolare hanno costituito in passato un ottimo mezzo per chiarire il ciclo ottico dei centriF in alogenuri alcalini e la natura dello stato eccitato rilassato. Abbiamo usato tale tecnica per studiare la debole doppia emissioneF trovata recentemente in NaI e la luminescenza dei centriF edF _A (di tipo I e II) in KCl. Si è trovato che l'emissioneF a minore energia in NaI e l'emissioneF _A (I) in KCl∶Na⁺ si comportano come la ben nota emissione dei centriF, il che conferma l'attribuzione di tale luminescenza in NaI allo stato eccitato rilassato normale. L'emissioneF a energia maggiore in NaI e l'emissioneF _A (II) in KCl∶Li⁺ mostrano un comportamento completamente diverso. I dati sperimentali sono stati confrontati con la teoria vibronica di Ham e Grevsmuhl dello stato eccitato rilassato.

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Резюме Магнитный круговой дихроизм ранее применялся как инструмент для выяснения оптического циклаF центров в щелочных галогенидах и природы релаксирующего возбужденного состояния. В этой работе мы используем эту технику для исследования слабого двойного F излучения, обнаруженного недавно в NaI и при люминесценцииF иF _A центров (типа I и типа II) в KCl. Мы обнаружили, что длинноволновоеF излучения в NaI иF _A (I) излучение в KCl∶Na⁺ ведет себя как хорошо известное излучениеF центров, что подтверждает приписывание вышеуказанной люминесценции в NaI нормальному релаксирующему возбужденному состоянию. Полностью отличное поведение обнаруживает коротковолновоеF излучение в NaI иF _A (II) излучение в KCl∶Li⁺. Полученные экспериментальные данные сравниваются с вибрационной теорией Гама и Гревсмула для релаксирующего возбужденного состояния.

     

Numerical studies on the anderson localization problem

The electron localization is studied for Anderson's tight-binding model with diagonal and off-diagonal disorder for a very large square lattice (10,000 sites) and diamond lattice (27,000 sites). The numerical investigations are based on the Lanczos recursion method. The convergence of the recursion coefficientsa _n ,b _n is discussed with regard to the electron localization.From Anderson's criterion and an exact real space renormalization method the energy of the localization edge is found as a function of the degree of disorder. Also the dependence of the spatial decay rate of localized wave functions on the energy and the degree of disorder is evaluated. Near the Anderson transition, where all states become localized, we get two critical exponentsv _E andv _W , which lead us to the tentative suggestion of multicritical scaling laws for this transition.     

The (d,p) Reactions below 3.0 MeV

Excitation functions for a number of proton groups for the reactions ²³Na(d, p)²⁴Na and ²⁷Al(d, p)²⁸Al were measured in the energy range E_d = 1.5 to 3.0 MeV. The angular distributions for a number of proton groups were measured at a number of deuteron energies below 3.0 MeV for the three reactions ¹²C(d, p)¹³C, ²³Na(d, p)²⁴Na and ²⁷Al(d, p)²⁸Al. The theory of deuteron stripping reactions at incident energies below the Coulomb barrier has been considered. A closed analytical form for the differential cross-section has been obtained considering three cases according to the incident deuteron and outgoing proton energies. An attempt has been made to fit the angular distribution measurements at a number of deuterons bombarding energies accordingly.     

Maximal operators of Fejér means of double Walsh-Fourier series

The main aim of this paper is to prove that the maximal operator of the Fejér mean of the double Walsh-Fourier series is not bounded from the Hardy space H _1/2 to the space weak-L _1/2. This paper was written during the visit of the author at the College of Nyíregyháza in Hungary.