Tyrosinase inhibitory potential of natural products isolated from various medicinal plants

Seven secondary metabolites, p-hydroxybenzoic acid (1), 3,4-dihydroxybenzoic acid (2), ferulic acid (3), 2,6-dimethoxy-4-hydroxy acetophenone (4), lupeol (5), 2'-O-ethylmurrangatin (6) and hibiscetin heptamethyl ether (7) were the natural products isolated from various medicinal plants. Their structures were identified by spectral comparison with previously reported data. The compounds 1-7 were screened for their tyrosinase-inhibitory activity. The compound p-hydroxybenzoic acid (1) was found to have potent activity against tyrosinase enzyme, whereas lupeol (5) showed significant activity.     

HF, MP2 and DFT calculations and spectroscopic study of the vibrational and conformational properties of N-diethylendiamine

The conformational stability and vibrational modes of the N-diethylendiamine organic cation (N-DD(2+)) were studied by experimental (Raman) spectroscopy combined with theoretical calculations. Various ab initio theories were used: Hartree-Fock (HF) theory, M?ller-Plesset second-order perturbation (MP2) theory and density functional theory (DFT). Three stable conformers of N-DD(2+), trans-trans, gauche-gauche and gauche-trans were calculated. A comparison between the computed structural parameters of the conformers at both levels of theory and the X-ray data was made. It is demonstrated that the N-DD(2+) cation adopts more probably the gauche-gauche conformation at room temperature. In order to make a more detailed interpretation of the low temperature phase transition of N-DDHP, the Raman spectra of N-DDHP were recorded at room and low temperature in the 200-3400 cm(-1) region. The vibrational frequencies of the different conformers of N-DD(2+) were also calculated using the DFT/B3LYP (6-31G(d)) level of theory. By comparison between the experimental and theoretical results, the conformational dynamic of the N-DD(2+) organic cation was confirmed. It is shown that the N-DD(2+) cation configuration changes from gauche-gauche conformer to gauche-trans conformer when decreasing the temperature.     

Composition operators on <Emphasis Type="Italic">f</Emphasis>-algebras

By a composition operator between two f-algebras we mean a positive algebra homomorphism. This paper intends to give a systematic study of such operators. A particular attention is paid to their connection with separating regular operators as well as to their global behavior in the module of regular operators. The paper ends with some open problems.     

Screening for potential quality markers of Callerya nitida var. hirsutissima. Z.Wei based on components profile,pharmacokinetics, and anti-inflammatory study

Callerya nitida var. hirsutissima. Z.Wei is a classical, traditional Chinese herbal medicine mostly used to treat rheumatoid arthritis. Recent reports suggest that inconsistent and poor-quality control levels have primarily affected the therapeutic efficacy. Therefore, the aim of the current study was to investigate the active chemical ingredients, stability of components in blood, pharmacokinetics, and pharmacodynamics to specify the potential markers for quality control and quality evaluation of Callerya nitida. The active components in vitro and in vivo were obtained by ultra-high-performance liquid chromatography-mass spectrometry. Moreover, the changes of the bioactive components in the blood were monitored over time (0–24 h) in order to identify stable active components. On this basis, the pharmacokinetic characteristics of these ingredients combined with the anti-inflammatory activity were determined to screen out the potential markers for ensuring the quality control of Callerya nitida. The identified four components, such as calycosin, daidzein, formononetin, and 5-hydroxymethylfurfural, have the characteristics of intrinsic components, clearly defined structures, high exposure values, and in vivo stability, which are important for the therapeutic activity of pharmacologically active materials. Therefore, they can be used as potential markers to control the quality levels of Callerya nitida.     

A projection method for the spectral solution of non‐homogeneous and incompressible Navier–Stokes equations

This paper is devoted to the development of a parallel, spectral and second‐order time‐accurate method for solving the incompressible and variable density Navier–Stokes equations. The method is well suited for finite thickness density layers and is very efficient, especially for three‐dimensional computations. It is based on an exact projection technique. To enforce incompressibility, for a non‐homogeneous fluid, the pressure is computed using an iterative algorithm. A complete study of the convergence properties of this algorithm is done for different density variations. Numerical simulations showing, qualitatively, the capabilities of the developed Navier–Stokes solver for many realistic problems are presented. The numerical procedure is also validated quantitatively by reproducing growth rates from the linear instability theory in a three‐dimensional direct numerical simulation of an unstable, non‐homogeneous, flow configuration. It is also shown that, even in a turbulent flow, the spectral accuracy is recovered. Copyright © 2012 John Wiley & Sons, Ltd.     

A direct synthesis of β-carbolines via a three-step one-pot domino approach with a bifunctional Pd/C/K-10 catalyst

A rapid, microwave-assisted synthesis of β-carbolines via a successive condensation/cyclization/dehydrogenation approach is described. This methodology involves the coupling of various tryptamines with aromatic aldehydes/glyoxals. The product imine undergoes a Pictet-Spengler cyclization followed by a final dehydrogenation to yield β-carbolines in a three-step domino reaction. The use of the bifunctional catalyst Pd/C/K-10 combined with microwave irradiation enabled the synthesis of β-carbolines in short reaction times and in good to excellent yields.     

Heisenberg uncertainty inequality for Gabor transform on nilpotent Lie groups

Analysis Mathematica - In this paper, we define and prove an analog of the Heisenberg uncertainty inequality for Gabor transform in the setup of connected, simply connected nilpotent Lie groups....     

A two-strain epidemic model with mutant strain and vaccination

In this paper, it is assumed that the spread of a pathogen can mutate in the host to create a second, cocirculating, mutant strain. Vaccinated individuals perhaps becomes infected after being in contact with individuals infected with mutant strain. A?two-strain epidemic model with vaccination is firstly investigated. The existence and stability properties of equilibria in this model are examined. By analyzing the characteristic equation and constructing Lyapunov functions, the conditions for local and global stability of the infection-free, boundary and endemic equilibria are established. The existence of Hopf bifurcation from the endemic equilibrium is also examined as this equilibrium loses its stability. Our theoretical results are confirmed by numerical simulations.