Phenylthiohydantoin Formation as a Novel Mode of Assay,Applied to S-Carboxymethylcysteine in Plasma

Abstract

The novel method now described, for S-carboxymethylcysteine in plasma at levels that may be lower than 20 μg/ml in therapeutic investigations, entails conversion into the corresponding phenylthiohydantoin (PTH) derivative, so as to confer ultraviolet detectability in a final separation step entailing reverse-phase HPLC. The conditions adopted take account of possible losses of the compound, associated with capricious water-solubility, of stability problems unexpectedly encountered with its PTH derivative, and of the risk of interferences from plasma constituents.     

Development and Validation of Derivative Spectrophotometric Method for Determination of Rabeprazole Sodium in Pharmaceutical Formulation

Abstract

The aim of this work is to develop and validate the derivative spectrophotometric method for determination of the proton pump inhibitor rabeprazole sodium in pharmaceutical formulations. The technique was applied using water (pH 10.0) as diluent. The first‐order derivative spectra were obtained at N=5, Δλ=4.0 nm, and determinations were made at 304 nm. The method showed high specificity in the presence of formulation excipients and good linearity in the concentration range of 6.0 to 18.0 µg/mL^?1. The intra‐ and interday precision data demonstrated the method has good reproducibility [Relative Standard Deviation ((RSD)=1.0 interdays)]. Accuracy was also evaluated and results were satisfactory (mean recovery of 99.15%). The detection and quantitation limits were 0.055 and 0.17 µg/mL^?1, respectively. The method was demonstrated to be adequate for routine analysis in quality control.     

Derivative Spectrophotometric Determination of Copper and Palladium Simultaneously by Using MDTC as a Reagent

Abstract

A selective, sensitive, and economical derivative spectrophotometric method has been developed for the determination of trace amount of Cu(II) and Pd(II) with MDTC as a reagent in the presence of CTAB, a solubilizing agent. The molar absorption coefficient and analytical sensitivities of the 1:2 Cu(MDTC)₂ and Pd(MDTC)₂ complexes are 2.467×10⁴ and 2.989×10⁴ l mol^?1, respectively. The developed derivative procedure, is applied for the rapid and selective simultaneous determination of Cu(II) and Pd(II) in the range of 0.2–15 and 0.1–10 µg/ml, respectively. Complex matrices, including alloys, biological samples, pharmaceutical samples and synthetic mixtures have been successfully analyzed for trace amounts of two metal ions.     

Existence of solutions for fractional differential equations with multi-point boundary conditions

We discuss the existence of solutions for a nonlinear multi-point boundary value problem of integro-differential equations of fractional order q ∈ (1, 2]. Our analysis relies on the contraction mapping principle and the Krasnoselskii’s fixed point theorem. Example is provided to illustrate the theory.     

Fractional differential equations of motion in terms of combined Riemann—Liouville derivatives

In this paper,we focus on studying the fractional variational principle and the differential equations of motion for a fractional mechanical system.A combined Riemann-Liouville fractional derivative operator is defined,and a fractional Hamilton principle under this definition is established.The fractional Lagrange equations and the fractional Hamilton canonical equations are derived from the fractional Hamilton principle.A number of special cases are given,showing the universality of our conclusions.At the end of the paper,an example is given to illustrate the application of the results.     

Hamilton formalism and Noether symmetry for mechanico—electrical systems with fractional derivatives

This paper presents extensions to the traditional calculus of variations for mechanico-electrical systems containing fractional derivatives.The Euler-Lagrange equations and the Hamilton formalism of the mechanico-electrical systems with fractional derivatives are established.The definition and the criteria for the fractional generalized Noether quasisymmetry are presented.Furthermore,the fractional Noether theorem and conseved quantities of the systems are obtained by virtue of the invariance of the Hamiltonian action under the infinitesimal transformations.An example is presented to illustrate the application of the results.     

Parametric studies on relationships between flutter derivatives of slender bridge (Ⅱ)

Based on curve fitting of coefficients of three component forces of the Messina Straits Bridge, and the previously proposed semi-analytical expressions of flutter deriva-tives of flexible structure, the change of flutter derivatives of slender bridge cross-section with respect to its aerodynamic center, rotational speed and angle variation is studied using a parametric method. The calculated results are compared with the measured ones, and expressions of flutter derivatives of the Messina Straits Bridge are derived. The in-trinsic relationships existing in flutter derivatives are validated again. It is shown that the influence of the rotational speed on flutter derivatives is not negligible. Therefore, it provides an additional semi-analytical approach for analyzing flutter derivatives of the bridge with streamlined cross-section to get its aerodynamic information.     

Fractional optimal control of a 2-dimensional distributed system using eigenfunctions

This paper presents an eigenfunctions expansion based scheme for Fractional Optimal Control (FOC) of a 2-dimensional distributed system. The fractional derivative is defined in the Riemann–Liouville sense. The performance index of a FOC problem is considered as a function of both state and control variables, and the dynamic constraints are expressed by a Partial Fractional Differential Equation (PFDE) containing two space parameters and one time parameter. Eigenfunctions are used to eliminate the terms containing space parameters and to define the problem in terms of a set of generalized state and control variables. For numerical computation Grünwald–Letnikov approximation is used. A direct numerical technique is proposed to obtain the state and the control variables. For a linear case, the numerical technique results into a set of algebraic equations which can be solved using a direct or an iterative scheme. The problem is solved for different number of eigenfunctions and time discretization. Numerical results show that only a few eigenfunctions are sufficient to obtain good results, and the solutions converge as the size of the time step is reduced.     

General solutions to a class of time fractional partial differential equations

A class of time fractional partial differential equations is considered, which in- cludes a time fractional diffusion equation, a time fractional reaction-diffusion equation, a time fractional advection-diffusion equation, and their corresponding integer-order partial differential equations. The fundamental solutions to the Cauchy problem in a whole-space domain and the signaling problem in a half-space domain are obtained by using Fourier- Laplace transforms and their inverse transforms. The appropriate structures of the Green functions are provided. On the other hand, the solutions in the form of a series to the initial and boundary value problems in a bounded-space domain are derived by the sine- Laplace or cosine-Laplace transforms. Two examples are presented to show applications of the present technique.     

Discovery of Fuchsone Derivatives as Novel Nonpeptide Inhibitor of Caspase-3

Many degenerative diseases caused by uncontrolled cell death can be intervened pharmaceutically through inhibiting caspase-3 activity that leads to cell apoptosis. Here is presented the discovery of rosolic acid and phe- nolphthalein methyl ester, which both belong to fuchsone derivatives, as novel and potent nonpeptide inhibitors of caspase-3. They show high inhibitory potency against caspase-3 in vitro(IC50=0.28 and 0.13 μmol/L). Molecular modeling study provided further an insight into the interaction of phenolphthalein methyl ester with activated caspase-3. The structures of the present small-molecule caspase-3 inhibitors are different from the structures of known caspase-3 inhibitors, so the inhibitors were likely to provide some information for the discovery of anti-caspase-3 inhibitors.