Regina M S Pereira

Universidade Federal do Pampa (Unipampa), Caçapava, Rio Grande do Sul, Brazil

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Publications (5)10.23 Total impact

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    ABSTRACT: The interaction of Pt(II)(dppf)-complex, namely [Pt(dppf)(H(2)O)(2)](2+) with DNA was investigated by DPV and (1)H-NMR techniques. The results showed that the interaction process has been characterized by changes in the electrochemical parameters of both compounds and the formation of a new anodic current peak close to the anodic current peak of the [Pt(dppf)(H(2)O)(2)](2+). In addition, the (1)H-NMR spectra show that the coordination of Pt(II)(dppf)-complex to dsDNA occurs via N(7) of guanine. Others parameters like pH and ionic strength that affect the interaction process were also investigated.
    Biology of Metals 12/2008; 22(2):385-92. · 3.17 Impact Factor
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    ABSTRACT: In this work the interaction of DNA and the flavonoid-transition metal complex (Cu(II)-naringin complex) is characterized. The interaction was evaluated by using electrochemical ssDNA- and dsDNA-based biosensors and the results were supported by UV, CD and (1)H NMR data. In the electrochemical method, changes in the oxidation peak of the guanine and adenine bases obtained by square wave voltammetry (SWV) showed evidence of the interaction. The variations of the spectroscopic characteristics of DNA and Cu(II)-naringin complex in aqueous medium demonstrated that the predominant interaction mode may be by intercalation. Cu(II)-naringin complex interacts to dsDNA probably via N(7) of guanine site.
    Journal of Pharmaceutical and Biomedical Analysis 01/2008; 45(5):706-13. · 2.95 Impact Factor
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    ABSTRACT: Coumarin is an active principle found in several vegetable species with a characteristic smell of vanilla. It is widely used as a perfume fixer, paint and spray additive, and in cleaning products. It also possesses clinical value due to antibiotic and analgesic properties, besides its potential use in the treatment of cancer and AIDS. The objective of this work was to obtain solubility data for coumarin under several conditions, as well as to evaluate process parameters for its extraction from emburana seeds with supercritical CO2. The process parameters studied were temperature, pressure, CO2 flow rate and particle size of the seeds. The solubility in supercritical CO2 was correlated using the Peng–Robinson equation. Solid-supercritical fluid and liquid-supercritical fluid equilibria were considered and correlated separately, with L-SC presenting better results due to the effect of the melting point depression of coumarin under high pressure. The results showed significant effects of pressure and temperature on the extraction yield and also, the smaller the particle size of the seeds, the better the yield.
    The Journal of Supercritical Fluids. 01/2008;
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    ABSTRACT: The antioxidant activity of flavonoids is believed to increase when they are coordinated with transition metal ions. However, the literature on this subject is contradictory and the outcome seems to largely depend on the experimental conditions. In order to understand the contribution of the metal coordination and the type of interaction between a flavonoid and the metal ion, in this study a new metal complex of Cu (II) with naringin was synthesized and characterized by FT-IR, UV-VIS, mass spectrometry (ESI-MS/MS), elemental analysis and 1H-NMR. The results of these analyses indicate that the complex has a Cu (II) ion coordinated via positions 4 and 5 of the flavonoid. The antioxidant, anti-inflammatory and antimicrobial activities of this complex were studied and compared with the activity of free naringin. The Naringin-Cu (II) complex 1 showed higher antioxidant, anti-inflammatory and tumor cell cytotoxicity activities than free naringin without reducing cell viability.
    Molecules 02/2007; 12(7):1352-66. · 2.43 Impact Factor
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    ABSTRACT: Reaction of diphosphine complexes [IrCl{(C6F5)2P(CH2)2P(C6F5)2}]2 (I) and [IrCl(dppe)]2 (II) with coordinating solvents (acetonitrile, acetone, DMSO) leads to several square-planar complexes of the type [IrCl(diphosphine)(solvent)] which are stable only in solution ([IrCl{(C6F5)2P(CH2)2P(C6F5)2}(NCCH3)] (III) and [IrCl{(C6F5)2P(CH2)2P(C6F5)2}(acetone)], IV) and/or can be detected only under APCI-MS/MS conditions ([IrCl(dppe)(solvent)]). When III is allowed to react with CO for at least 30 min, the unusual five coordinated trans-dicarbonyl complex [IrCl{(C6F5)2P(CH2)2P(C6F5)2}(CO)2] (Vb) is formed, as characterized by 1H and 31P NMR, FT-IR, TGA and APCI-MS/MS.A new and stable square-planar complex [Ir(OCH3)(cod)(PClPh2)] (IX) was also synthesized. Its APCI-MS/MS spectrum is simple and unique as it shows exclusively the loss of a neutral C3H2 species. Along with the APCI-MS and APCI-MS/MS analyses, whenever it was possible all complexes were also characterized by 1H and 31P NMR spectroscopy.
    Inorganica Chimica Acta 05/2004; 357(7):2100-2106. · 1.69 Impact Factor