Capillary zone electrophoretic separation and determination of imidazolic antifungal drugs

Capillary zone electrophoresis (CZE) was adapted to the simultaneous determination of a mixture of three imidazolic antifungal drugs. Separation was achieved by using a fused-silica capillary column with an acetic acid-Tris buffer at pH 5.18 and UV detection at 196 nm. Several electrophoretic parameters were investigated: pH and buffer concentration, applied voltage, temperature and injection conditions. The optimized CZE method was applied to the individual determination of ketoconazole, clotrimazole and econazole in pharmaceutical forms, after a previous single extraction step in methanol, with recoveries of 98.00, 99.96 and 99.58% respectively. The antifungal drugs can be determined at a concentration level lower than 1.0 x 10(-7) M.     

Non-emissive RuII Polypyridyl Complexes as Efficient and Selective Photosensitizers for the Photooxidation of Benzylamines

Five new Ru^II polypyridyl complexes bearing N-(arylsulfonyl)-8-amidoquinolate ligands and three of their biscyclometalated Ir^III congeners have been prepared and employed as photocatalysts ( PC s) in the photooxidation of benzylamines with O₂. In particular, the new Ru^II complexes do not exhibit photoluminescence, rather they harvest visible light efficiently and are very stable in solution under irradiation with blue light. Their non-emissive behavior has been related to the low electrochemical energy gaps and rationalized on the basis of theoretical calculations (DFT analysis) that predict low S₀←T₁ energy values. Moreover, the Ru^II complexes, despite being non-emissive, display excellent activities in the selective photocatalytic transformation of benzylamines into the corresponding imines. The presence of an electron-withdrawing group (-CF3) on the arene ring of the N-(arylsulfonyl)-8-amidoquinolate ligand improves the photocatalytic activity of the corresponding photocatalyst. Furthermore, all the experimental evidence, including transient absorption spectroscopy measurements suggest that singlet oxygen is the actual oxidant. The Ir^III analogues are considerably more photosensitive and consequently less efficient photosensitizers ( PS s).     

Synthesis of Symmetrical and Nonsymmetrical Polyenes by Iterative and Bidirectional Palladium-Catalyzed Cross-Coupling Reactions

Bifunctional unsaturated reagents designed to undergo palladium-catalyzed cross-coupling reactions with complementary polyenyl connective fragments are highly useful for the undoubtedly challenging synthesis of polyenes. The current toolkit of building blocks for the bidirectional formation of Csp²−Csp² single bonds of polyenes includes homo-bisfunctionalized reagents with equal or unequal reactivity (due to steric and/or electronic factors), and hetero-bisfunctionalized counterparts containing either two different nucleophiles, two electrophiles or one of these functionalities and a latent nucleophile that can be unmasked when desired. The combination of these bifunctional linchpin reagents using tactics that modulate the reactivity of each terminus in order to achieve the required connection have streamlined the synthesis of polyenes of great complexity using (iterative) cross-coupling methods for Csp²−Csp² bond formation. Reaction conditions for the Pd-catalyzed cross-coupling reactions are mild and functional-group-tolerant, and therefore these protocols allow to construct the polyene structures using shorter unsaturated reactants with the desired geometries, since in general the products preserve the stereochemical information of the connected cross-coupling partners.     

Crystal structures and thermal decomposition oftrans-Pd(Creat)2Cl2·2H2O andcis-Pt(Creat)2I2·3H2O

New complexes of the formulaetrans-Pd(Creat)₂Cl₂·2H₂O (I) andcis-Pt(Creat)₂I₂·3H₂O (II) have been prepared and their structures and stabilities studied by X-ray diffraction and thermal analysis. Both compounds have a squareplanar geometry, the two Cl atoms and N1 creatinine atoms are coordinated to Pd intrans configuration, while in compoundII the I atoms and N1 atoms are coordinated incis configuration. In spite of the earlier differences, the TG and DTA curves of the complexes show that their stability is very similar. Since an extended hydrogen bond system is present in the crystals, especially inII, the possible consequences in biological media are discussed briefly.

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Kristallstrukturen und thermische Zersetzung vontrans-Pd(Creat)₂Cl₂·2H₂O undcis-Pt(Creat)₂I₂·3H₂O

Zusammenfassung Es wurden neue Komplexe der Formelntrans-Pd(Creat)₂Cl₂·2H₂O (I) undcis-Pt(Creat)₂I₂·3H₂O (II) hergestellt und ihre Strukturen und Stabilitäten mittels Röntgenstrukturanalyse bzw, thermischer Analyse untersucht. Beide Komplexe haben quadratisch-planare Struktur, die zwei Cl-Atome und die N1-Creatinin-Atome sind an Pd intrans-Konfiguration koordiniert, währenddessen in VerbindungII die I-Atome und die N1-Atome incis-Konfiguration zueinander stehen. Trotz früherer Differenzen zeigen die TG- und DTA-Kurven der Komplexe, daß ihre Stabilitäten sehr ähnlich sind. Da besonders inII ein ausgedehntes Wasserstoffbindungssystem vorhanden ist, werden auch mögliche Konsequenzen bezüglich biologischer Wirksamkeit kurz diskutiert.

     

Research in the azole series. 103. Synthesis and 13C NMR study of pyrazole-4-carboxaldehydes

Ten new pyrazoles have been prepared and their ¹³C nmr chemical shifts compared with those of twelve other pyrazoles, some of them prepared purposely for this study. The chemical shifts are discussed statistically assuming that they are additive. A formyl group in the position 4 of the pyrazole ring produces a large effect on carbon C₄ (SCS = 17.3 ppm) and medium effects on carbons C₃ (SCS = 1.9 ppm) and C₅ (SCS = 3.8 ppm). The azines derived from pyrazole-4-carboxaldehydes are of the E,E-configuration.     

Spectroscopic studies of stratum corneum model membrane from Bothrops jararaca treated with cationic surfactant

This research employed FT-Raman and PAS-FTIR spectroscopic techniques to evaluate the interaction of cetyl trimethyl ammonium chloride (CTAC), a cationic surfactant, on the stratum corneum (SC) of shed snake skins from Bothrops jararaca, used as model membranes. Surfactant aqueous solutions (50.0 and 0.78 gl(-1)) with neutral pH were applied on the samples with intervals of 4, 8 (whole SC) and 12h (SC tape-stripped). Samples presented modifications of the topography for all conditions of the assays and the monomers of the surfactant, instead of the micelles, seemed to interact with the keratin. The SC model membranes treated with CTAC have had an augment of water content (except for whole SC treated for 8h) indicated by the expansion of the band 3600-3300 cm(-1), mainly for the tape-stripped samples after 12h treatment. Concentration appeared to be an important factor related to an increase of the tissue hydration.     

Diterpenes from teucrium capitatum L. X-ray crystal and molecular structure of capitatin

Two diterpenes, capitatin 4 and teucapitatin 5 have been isolated from Teucrium capitatum. The X-ray structure of 4, including absolute stereochemistry, is given. Diterpene 4 has been chemically related to picropolin 1 and picropolinone 2, thereby establishing the absolute stereochemistry of these two neoclerodane-type diterpenes.     

Determination of diclofenac sodium in eagle's minimum essential medium with Earle's balanced salt solution

A validated method was developed for determination of diclofenac sodium, considered a model hydrophilic drug for in vitro permeation studies, in Eagle's Minimum Essential Medium (MEM) with Earle's balanced salt solution. Liquid chromatography was used to determine diclofenac sodium. This method was developed with a reversed-phase column Supercosil LC 18, DB 25 cm x 4.5 mm; the mobile phase was methanol with 3% (v/v) acetic acid-Milli-Q water (74 + 26), and detection was at 283 nm. The detection and quantitation limits were 2.41 x 10(-8) and 3.31 x 10(-5) microg/microL, respectively. The accuracy within-day (n = 3) and day-to-day (n = 7) was 98.83%; the mean variation coefficient for inter- (n = 7) and intraday precision (n = 3) was 12.20%, thus, not exceeding 15%. This method can be used as an analytical procedure for the determination of diclofenac sodium in MEM for in vitro permeation studies.     

Evolution of carrier and optical phonon distribution in photoexcited semiconductors

A study of the time evolution of a coupled photoexcited electron-LO phonon system is presented. Zubarev's method to deal with irreversible relaxation processes is used to derive the dynamic equation for the distribution functions. We report results which allow to remove some inconsistencies and controversies concerning early models proposed for the interpretation of measurements of the ratio Stokes to anti-Stokes intensities in the LO-phonon Raman spectrum.