Application of HPLC-NMR coupling using C30 phase in the separation and identification of flavonoids of taxonomic relevance

The on-line separation and identification of two important taxonomic markers for plant species of the Paepalanthus genus, the flavonoids 6-methoxykaempferol-3-O-β-D-glucopyranoside and 6-methoxykaempferol-3-O-β-D-6″(p-coumaroyl)glucopyranoside, has been performed with an HPLC-NMR coupling using C30 phase. 1D spectra have been recorded in the stopped-flow mode for the two predominant chromatographic peaks. This is the first application of HPLC-NMR coupling using C30 phase to a taxonomic problem. The technique drastically reduces the required amount of sampling for structure determination. © Springer-Verlag 2000.

Solid-state NMR, ionic conductivity, and thermal studies of lithium-doped siloxane-poly(propylene glycol) organic-inorganic nanocomposites

Hybrid organic-inorganic ionic conductors, also called ormolytes (organically modified electrolytes), were obtained by dissolution of LiClO 4 in siloxane-poly(propylene glycol) matrixes. The dynamic features of these nanocomposites were studied and correlated to their electrical properties. Solid-state nuclear magnetic resonance (NMR) spectroscopy was used to probe the effects of the temperature and nanocomposite composition on the dynamic behaviors of both the ionic species ( 7Li) and the polymer chains ( 13C). NMR, dc ionic conductivity, and DSC results demonstrate that the Li + mobility is strongly assisted by the segmental motion of the polymer chain above its glass transition temperature. The ac ionic conductivity in such composites is explained by use of the random free energy barrier (RFEB) model, which is agreement with their disordered and heterogenous structures. These solid ormolytes are transparent and flexible, and they exhibit good ionic conductivity at room temperature (up to 10 -4 S/cm). Consequently, they are very promising candidates for use in several applications such as batteries, sensors, and electrochromic and photoelectro-chemical devices.

Array of Bose-Einstein condensates under time-periodic Feshbach-resonance management

The investigation of the dynamics of a discrete soliton in an array of Bose-Einstein condensates under the action of a periodically time-modulated atomic scattering length [Feshbach-resonance management (FRM)] was discussed. The slow and rapid modulations, in comparison with the tunneling frequency were considered. An averaged equation, which was a generalized discrete nonlinear Schrödinger equation, including higher-order effective nonlinearities and intersite nonlinear interactions was derived in the case of the rapid modulation. It was demonstrated that the modulations of sufficient strength results in splitting of the soliton by direct simulations.

Macromolecular array patterns of silk gland secretion in social Hymenoptera larvae

The cocoon, produced by most holometabolous insects, is built with silk that is usually produced by the larval salivary gland. Although this silk has been widely studied in the Lepidoptera, its composition and macromolecular arrangement remains unknown in the Hymenoptera. The macromolecular array patterns of the silk in the larval salivary gland of some meliponids, wasps, and ants were analyzed with polarized-light microscopy, and they were compared with those of Bombyx mori (Lepidoptera). There is a birefringent secretion in the glandular lumen of all larvae, due to filamentous structural proteins that display anisotropy. The silk in the distal, middle and proximal regions of the secretory portion of Formicidae and Vespidae glands presented a lattice optical pattern. We found a different pattern in the middle secretory portion of the Meliponini, with a zigzag rather than a lattice pattern. This indicates that the biopolymer fibers begin their macromolecular reorganization at this glandular region, different from the Formicidae and the Vespidae, in which the zigzag optical pattern was only found at the lateral duct. Probably, the mechanism of silk production in the Hymenoptera is a characteristic inherited from a common ancestor of Vespoidea and Sphecoidea; the alterations in the pattern observed in the Meliponini could be a derived characteristic in the Hymenoptera. We found no similarity in the macromolecular reorganization patterns of the silk between the Hymenoptera species and the silkworm.

Determination of saturates, aromatics and ethanol in Brazilian commercial gasoline with low olefin content using 1 H NMR spectroscopy

In this work, a Hydrogen Nuclear Magnetic Resonance (1H NMR) method has been developed to determine aromatics and ethanol in Brazilian commercial gasoline with low olefin content. The proposed method involves subdividing an 1H NMR spectrum into regions, each of which is assumed to be associated with a specific type of structural group (OH, CH, CH2 and CH3). The method is based on the assignment of overlapping regions of 1H NMR spectra due to the signals of naphthene (N), iso and normal paraffins (P) and ethanol (E). Each 1H NMR spectrum was divided into 8 regions and the integration was correlated to the percentage of the substances to be determined. The results of the analysis by 1H NMR were compared with analysis of GC-FID obtained with the PONA system. The proposed technique of 1H NMR was shown to be an appropriate method for this sample type.

β-lactam antibiotics epitope mapping with STD NMR spectroscopy: A study of drug-human serum albumin interaction

Molecular recognition events are key issues in many biological processes. STD NMR (saturation transfer difference nuclear magnetic resonance spectroscopy) is one of the techniques used to understand such biological interactions. Herein, we have investigated the interactions of four β-lactam antibiotics belonging to two classes (cephalosporins and penicillins) with human serum albumin (HSA) by 1H STD NMR revealing that the interaction between the aromatic moiety and HSA is responsible for the binding efficiency. Thus, the structural differences from the five to six-membered thio ring in penicillins and cephalosporins do not seem to influence antibiotic-albumin interactions. © 2012 Sociedade Brasileira de Química.

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI-MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (1H-13C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple-Bond Correlation (HMBC), 1H-15N HMBC, 1H- 1H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p-Cl and p-Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p-NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.

Characterization of flavonoids and phenolic acids in Myrcia bella cambess. Using FIA-ESI-IT-MSn and HPLC-PAD-ESI-IT-MS combined with NMR

The leaves of Myrcia DC. ex Guill species are used in traditional medicine and are also exploited commercially as herbal drugs for the treatment of diabetes mellitus. The present work aimed to assess the qualitative and quantitative profiles of M. bella hydroalcoholic extract, due to these uses, since the existing legislation in Brazil determines that a standard method must be developed in order to be used for quality control of raw plant materials. The current study identified eleven known flavonoid-O-glycosides and six acylated flavonoid derivatives of myricetin and quercetin, together with two kaempferol glycosides and phenolic acids such as caffeic acid, ethil galate, gallic acid and quinic acid. In total, 24 constituents were characterized, by means of extensive preparative chromatographic analyses, along with MS and NMR techniques. An HPLC-PAD-ESI-ITMS and FIA-ESI-IT-MSn method were developed for rapid identification of acylated flavonoids, flavonoid-O- glycosides derivatives of myricetin and quercetin and phenolic acids in the hydroalcoholic M. bella leaves extract. The FIA-ESI-IT-MS techinique is a powerful tool for direct and rapid identification of the constituents after isolation and NMR characterization. Thus, it could be used as an initial method for identification of authentic samples concerning quality control of Myrcia spp extracts. © 2013 by the authors.

Prospecção química e avaliação das atividades e alelopática de Myrcia bella Cambess

Pós-graduação em Ciências Biológicas (Botânica) - IBB

Estudo químico e biológico do fungo endofítico Phomopsis sp. isolado da Senna spectabilis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prospecção química e biológica do fungo endofítico Camarops sp. isolado de Alibertia macrophylla

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Detecção in silico e caracterização dos constituintes micromoleculares majoritários do fungo endofítico Colletotrichum gloeosporioides isolado de folhas de Garcinia xanthochymus usando HPLC-DAD-HRMS e GC-MS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Genes candidatos a marcadores tumorais na progressão do adenocarcinoma de próstata indentificados por análise de HR-CGH e CGH-ARRAY

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudos químicos e biológicos de espécies do gênero Lippia (Verbenaceae) nativas no Cerrado paulista

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ultrasonic non-destructive testing of plate-like structures using piezoelectric array transducers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)