Validation of UV spectrophotometric and nonaqueous titration methods for the determination of carvedilol in pharmaceutical formulations

Ultraviolet (UV) spectrophotometric and nonaqueous volumetric methods are described for the determination of carvedilol in pharmaceutical formulations. Linearity, precision, and accuracy were evaluated according to the validation guidelines of the International Conference on Harmonization and the United States Pharmacopeia for both methods. The UV spectrophotometric procedure was performed in ethanol at 244 nm. Good linearity was obtained between 2 and 7 microg/mL with a correlation coefficient of 0.9999. The intra- and interday precision values were <2% for all samples analyzed. The accuracy, determined from recovery studies, was between 97.5 and 102.2%. The other procedure was based on the volumetric quantitation of carvedilol in a nonaqueous medium with 0.01 M perchloric acid and 1% violet crystal as the indicator. The validation of the volumetric method yielded good results that included linearity (r of > 0.999), precision (relative standard deviations of <2% for intra- and interday precision), and accuracy (96.4-102.4%). The methods were applied to tablets and compounded capsules. Statistical analysis by analysis of variance showed no significant difference between the results obtained by the proposed methods.     

A liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometric (LC‐APPI‐MS/MS) method for the determination of triterpenoids in medicinal plant extracts

An analytical method using liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometry with toluene as a dopant was developed for the determination of triterpenes in medicinal plant extracts. The 12 compounds determined have been shown to exhibit biological activity, such as gastroprotective, hepatoprotective, anti‐inflammatory, antiviral and anti‐tumor effects. The parameters of the atmospheric pressure photoionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection and quantification ranged from 0.4 to 157.9 µg l^?1 and 1.3 to 526.4 µg l^?1, respectively. The method was validated and applied to extracts of five medicinal plants species (Mansoa alliacea (Lam.) A.H.Gentry, Bauhinia variegata var variegata, Bauhinia variegata var alboflava, Cecropia obtuse Trécul and Cecropia palmate Willd) from the Amazonian region. The concentrations of the six triterpenes quantified in the samples ranged from 0.424 mg kg^?1 for ursolic acid to 371.96 mg kg^?1 for β‐amyrin, which were quantified by using the standard addition method (n = 3). Copyright © 2016 John Wiley & Sons, Ltd.     

Structure and properties of dinuclear manganese(III) complexes with pentaanionic pentadentate ligands including alkoxo, amido, and phenoxo donors

Doubly bridged mu-alkoxo-mu-X (X = pyrazolato or acetato) dinuclear MnIII complexes of 2-hydroxy-N-{2-hydroxy-3-[(2-hydroxybenzoyl)amino]propyl}benzamide) (H5L1) and 2-hydroxy-N-{2-hydroxy-4-[(2-hydroxybenzoyl)amino]butyl}benzamide (H5L2), [Mn2(L)(pz)(MeOH)4].xMeOH (1, L = L1, x = 0.5; 2, L = L2, x = 0; Hpz = pyrazole) and [Mn2(L1)(OAc)(MeOH)4] (3), have been prepared, and their structure and magnetic properties have been studied. The X-ray diffraction analysis of 1 (C24.5H34Mn2N4O9.5, triclinic, P, a = 12.2050(7) A, b = 12.7360(8) A, c = 19.2780(10) A, alpha = 99.735(5) degrees , beta = 96.003(4) degrees , gamma = 101.221(5) degrees , V = 2867.6(3) A3, Z = 4), 2 (C25H34Mn2N4O9, triclinic, P, a = 9.4560(5) A, b = 11.0112(5) A, c = 13.8831(6) A, alpha = 90.821(4) degrees , beta = 92.597(4) degrees , gamma = 93.403(4) degrees , V = 1441.29(12) A3, Z = 2), and 3 (C23H32Mn2N2O11, triclinic, P, a = 10.511(5) A, b = 11.713(5) A, c = 13.135(5) A, alpha = 64.401(5) degrees , beta = 74.000(5) degrees , gamma = 66.774(5) degrees , V = 1329.3(10) A3, Z = 2) revealed that all complexes consist of dinuclear units which are further extended into 1D (1 and 3) and 2D (2) supramolecular networks via hydrogen-bonding interactions. Magnetic susceptibility data evidence antiferromagnetic interactions for all three complexes: J = -3.6 cm-1, D approximately 0 cm-1, g = 1.93 (1); J = -2.7 cm-1, D = 0.8 cm-1, g = 1.93 (2); J = -4.9 cm-1, D = 3.8 cm-1, g = 1.95 (3).     

Synthesis of 3′-deoxy-3′-iminodiacetic acid and 3′-deoxy-3′-aminodiethanol thymidine analogues and NMR study of their complexation with boronic acids

The iminodiacetic acid and aminodiethanol moieties are known for their ability to generate with boronic acids bicyclic structures having a strong intramolecular NB coordination. We describe here the convergent synthesis of 3′-deoxy-3′-iminodiacetic acid and 3′-deoxy-3′-aminodiethanol thymidine analogues. The abilities of these compounds to form boronate complexes with aliphatic or aromatic boronic acids were established by 1D and 2D ¹H and ¹³C NMR. Moreover, conformational analysis of the newly synthesized compounds revealed a marked preference for an N-type sugar puckering.     

The role of temperature in the synthesis of hybrid inorganic-organic materials: the example of cobalt succinates

Five different cobalt succinate materials synthesized from an identical starting mixture using temperature as the only independent variable show increasing condensation and density at higher synthesis temperatures.     

Direct synthesis and aqueous solution properties of Y-shaped, stimulus-responsive block copolymer surfactants

We report the direct synthesis of a wide range of well-defined, Y-shaped stimulus-responsive block copolymers under mild conditions; the aqueous solution behaviour of these new polymeric surfactants has been investigated.     

(Eta5-pentamethylcyclopentadienyl)rhodium and -iridium complexes with weakly and strongly coordinating anions: isolation and first X-ray molecular structures of the tris(solvent) complexes [(C5Me5)M(acetone)2(H2O)][BF4]2 (M = Rh, Ir)

Several novel pentamethylcyclopentadienyl complexes of general formula [(C5Me5)IrL3][BF4]2 were prepared including the tris(solvent) precursors [(C5Me5)M(acetone)2(H2O)][BF4]2 (M = Rh, Ir) (1a,b). The X-ray molecular structures of 1a,b were determined at low temperature. Complexes 1a,b are isostructural, and both compounds crystallize in the monoclinic space group P2(1)/c with a = 10.157(3) A, b = 14.038(9) A, c = 16.335(2) A, beta = 99.73(2) degrees, and Z = 4 for 1a and with a = 10.107(9) A, b = 13.994(16) A, c = 15.996(34) A, beta = 99.61(12) degrees, and Z = 4 for 1b. The coordinated water molecule is hydrogen bonded to both BF4(-) anions. Reaction of 1a,b with pyridine (py) afforded the related tris(pyridine) complexes [(C5Me5)M(eta1-(N)-py)3][BF4]2 (M = Rh, Ir) (2a,b). Complex 2b was characterized by X-ray crystallography, monoclinic space group P2(1)/c with a = 8.665(3) A, b = 19.687(7) A, c = 18.408(5) A, beta = 94.17(3) degrees, and Z = 4. Moreover, we prepared the novel neutral compounds (C5Me5)M(eta2-NO3)(eta1-NO3) (M = Rh, Ir) (4a,b) where the anions are bonded to the metal center instead of a coordinating solvent as confirmed by X-ray study on the iridium complex 4b. The latter crystallizes in the orthorhombic space group Pcab with a = 13.032(4) A, b = 14.370(11) A, c = 14.839(18) A, and Z = 8.     

Hexacyanometalate molecular chemistry: di-, tri-, tetra-, hexa- and heptanuclear heterobimetallic complexes; control of nuclearity and structural anisotropy

Following a bottom-up approach to nanomaterials, we present a rational synthetic route to high-spin and anisotropic molecules based on hexacyanometalate [M(CN)(6)](3-) cores. Part 1 of this series was devoted to isotropic heptanuclear clusters; herein, we discuss the nuclearity and the structural anisotropy of nickel(II) derivatives. By changing either the stoichiometry, the nature of the terminal ligand, or the counterion, it is possible to tune the nuclearity of the polynuclear compounds and therefore to control the structural anisotropy. We present the synthesis and the characterisation by mass spectrometry, X-ray crystallography and magnetic susceptibility of bi-, tri-, tetra-, hexa- and heptanuclear species [M(CN)(n)(CN-M'L)(6-n)](m+) (with n=0-5; M=Cr(III), Co(III), M'=Ni(II); L=pentadentate ligand). Thus, with M=Cr(III), d(3), S=3/2, a dinuclear complex [Cr(III)(CN)(5)(CN-NiL(n))](9+), (L(n)=polydentate ligand) was built and characterised, showing a spin ground state, S(G)=5/2, with a ferromagnetic interaction J(Cr,Cu)=+18.5 cm(-1). With M=Co(III) (d(6), S=0) were built di-, tri-, tetra-, hexa and hepanuclear CoNi species: CoNi, CoNi(2), CoNi(3), CoNi(5) and CoNi(6). By a first approximation, they behave as one, two, three, five and six isolated nickel(II) complexes, respectively, but more accurate studies allow us to evaluate the weak antiferromagnetic coupling constant between two next-nearest neighbours M'-Co-M'.