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Abstract: Leishmaniasis is one of the most important parasitic neglected disease. The electrochemical evaluation of the antileishmanial drug miltefosine‐dsDNA interaction was investigated in incubated solutions and using dsDNA‐electrochemical biosensors, following the changes in the oxidation peaks of guanosine and adenosine residues, and the occurrence of the free guanine residues, electrochemical signal. The electrochemical behaviour of miltefosine was also investigated, at a glassy carbon electrode, using cyclic, differential pulse and square wave voltammetry and no electrochemical redox processes were observed. The interaction mechanism of miltefosine‐dsDNA occurs in two ways: independent of the dsDNA sequence, and leading to the condensation/aggregation of DNA strands, producing a rigid miltefosine‐dsDNA complex structure, and a preferential interaction between the guanine hydrogen atoms in the C−G base pair and miltefosine, causing the release of guanine residues detected on the electrode surface. Miltefosine did not induce oxidative damage to DNA in the experimental conditions used. [ABSTRACT FROM AUTHOR]

Daptomycin was the first approved drug from a new class of antimicrobials, the cyclic lipopeptides, and presents a broad spectrum of activity against a wide range of gram-positive bacteria. The daptomycin redox behaviour, by cyclic, differential pulse and square wave voltammetry, in a wide pH range, at a glassy carbon electrode, was investigated. The daptomycin oxidation was a two-step irreversible diffusion-controlled process and the diffusion coefficient DDPT = 2.32 × 10−5 cm2 s−1, was calculated. A detection limit LOD = 0.32 μM, was obtained. For the first time daptomycin, in fetal bovine serum biological fluid, using DP voltammetry, was determined. [ABSTRACT FROM AUTHOR]

The in situ evaluation of the direct interaction of chromium species with double-stranded DNA (dsDNA) was studied using differential pulse voltammetry at a glassy carbon electrode. The DNA damage was electrochemically detected following the changes in the oxidation peaks of guanosine and adenosine bases. The results obtained revealed the interaction with dsDNA of the Cr(IV) and Cr(V) reactive intermediates of Cr(III) oxidation by O dissolved in the solution bound to dsDNA. This interaction leads to different modifications and causes oxidative damage in the B-DNA structure. Using polyhomonucleotides of guanine and adenine, it was shown that the interaction between reactive intermediates Cr(IV) and Cr(V)-DNA causes oxidative damage and preferentially takes place at guanine-rich segments, leading to the formation of 8-oxoguanine, the oxidation product of guanine residues and a biomarker of DNA oxidative damage. The interaction of Cr(VI) with dsDNA causes breaking of hydrogen bonds, conformational changes, and unfolding of the double helix, which enables easier access of other oxidative agents to interact with DNA, and the occurrence of oxidative damage to DNA. [ABSTRACT FROM AUTHOR]

The antidiabetic drug metformin (MET) is one of a group of emerging pharmaceutical drug contaminants in the wastewater treatment plants. The electrochemical behaviour of MET−Cu(II) complex by differential pulse and square wave voltammetry, in a wide pH range, at a glassy carbon electrode modified with a carbon black dihexadecylphosphate film (CB−DHP/GCE), was investigated. The MET−Cu(II) complex oxidation showed one pH‐dependent process, which leads to the formation of an oxidation product, being oxidized at a lower potential. The electroanalytical MET−Cu(II) complex detection limit, LOD=0.63 μM, and quantification limit, LOQ=2.09 μM, were obtained, and the MET−Cu(II) complex determination in wastewater samples collected from a senior residence effluent, using the CB−DHP/GCE, was achieved. Considering MET toxicity, the electrochemical evaluation of MET−dsDNA interaction, in incubated solutions and using dsDNA‐electrochemical biosensors, following the changes in the oxidation peaks of guanosine and adenosine residues electrochemical currents, was also investigated. The MET−dsDNA interaction mechanism, for shorter times, occurs by the binding of MET molecules in the minor grooves of the dsDNA, and for long times, the stabilization of the MET−dsDNA complex, causing a local distortion and/or unwinding of dsDNA morphology, is described. However, MET did not promote DNA oxidative damage. [ABSTRACT FROM AUTHOR]

Isotretinoin redox behaviour, by voltammetry, at the cathodic pre-treated boron doped diamond electrode by cyclic, differential pulse and square wave voltammetry, and by spectrophotometry in a wide pH range, was investigated. The isotretinoin oxidation was an irreversible, diffusion-controlled process, occurred in a three-step cascade mechanism, and the isotretinoin diffusion coefficient D13-cis-RA=7.35×10−6 cm2 s−1, was calculated. The UV-Vis isotretinoin maximum absorption was pH-dependent. The detection limits LOD=0.53 μM, by differential pulse voltammetry, and LOD=0.38 μM, by UV-Vis spectroscopy, were obtained. The isotretinoin in the pharmaceutical drug Roacutan®, using differential pulse voltammetry, was determined. [ABSTRACT FROM AUTHOR]

Abstract: A selected series of new different substituted 3-arylcoumarins have been designed, synthesized, and evaluated their electrochemical redox mechanisms. The relevant structural information about coumarins was considered in order to better understand the structure/electrochemical relationship. The influence of bromine, methyl or other hydroxyl groups in different positions of the coumarin scaffold, by cyclic, differential pulse and square wave voltammetry at a glassy carbon electrode at different pHs was investigated. A comparative study of differently substituted 8-hydroxy-3-arylcoumarins was performed. [Copyright &y& Elsevier]

The interaction of double-stranded DNA with two poly-nuclear Pd(II) chelates with the biogenic polyamines spermidine (Spd) and spermine (Spm), Pd(II)-Spd and Pd(II)-Spm, as well as with the free ligands Spd and Spm, was studied using atomic force microscopy (AFM) at a highly oriented pyrolytic graphite (HOPG) surface, volta-mmetry at a glassy carbon (GC) electrode, and gel elec-trophoresis. The AFM and voltammetric results showed that the interaction of Spd and Spm with DNA occurred even for a low concentration of polyamines and caused no oxidative damage to DNA. The Pd(II)-Spd and Pd(II)-Spm complexes were found to induce greater morphological changes in the dsDNA conformation, when compared with their ligands. The interaction was specific, inducing distortion and local denaturation of the B-DNA structure with release of some guanine bases. The DNA strands partially opened give rise to palladium intra- and interstrand cross-links, leading to the formation of DNA adducts and aggregates, particularly in the case of the Pd(II) Spd complex. [ABSTRACT FROM AUTHOR]

The drugs of abuse cocaine (C), heroin (H), and morphine (M) have been studied to enable understanding of the occurrence of cocaine–opioid interactions at a molecular level. Electrochemical, Raman, and NMR studies of the free drugs and their mixtures were used to study drug–drug interactions. The results were analyzed using data obtained from quantum-mechanical calculations. For the cocaine–morphine mixture (C–MH), formation of a binary complex was detected; this involved the 3-phenolic group and the heterocyclic oxygen of morphine and the carbonyl oxygen and the methyl protons of cocaine’s methyl ester group. NMR studies conducted simultaneously also revealed C–MH binding geometry consistent with theoretical predictions and with electrochemical and vibrational spectroscopy results. These results provide evidence for the occurrence of a cocaine–morphine interaction, both in the solid state and in solution, particularly for the hydrochloride form. A slight interaction, in solution, was also detected by NMR for the cocaine–heroin mixture. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Atomic force microscopy and differential pulse voltammetry were used to characterize the interaction of small highly structured ribozymes with two carbon electrode surfaces. The ribozymes spontaneously self-assemble in two-dimensional networks that cover the entire HOPG surface uniformly. The full-length ribozyme was adsorbed to a lesser extent than a truncated RNA sequence, presumably due to the formation of a more compact overall structure. All four nucleobases composing the ribozyme could be detected by anodic voltammetry on glassy carbon electrodes, and no signals corresponding to free nucleobases were found, indicating the integrity of the ribozyme molecules. Mg2+ cations significantly reduced the adsorption of ribozymes to the surfaces, in agreement with the stabilization of this ribozyme's compact, stable, and tightly folded tertiary structure by Mg2+ ions that could prevent the hydrophobic bases from interacting with the HOPG surface. Treatment with Pb2+ ions, on the other hand, resulted in an increased adsorption of the RNA due to well-known hydrolytic cleavage. The observed dependence of anodic peak currents on different folding states of RNA may provide an attractive method to electrochemically monitor structural changes associated with RNA folding, binding, and catalysis. [ABSTRACT FROM AUTHOR]

Few analytical methods are currently available for determination of apomorphine, the active substance of a new oral formulation used in the treatment of erectile dysfunction. In this way a flow injection electrochemical method (FIA-EC) was developed for its quantification and applied to pharmaceutical dosage forms. Based in previous findings regarding the stability of apomorphine in borate buIer and after optimization of several analytical parameters a single channel flow injection manifold was set up that enables the determination of this drug over the concentration range of 3 to 16 μmol L[SUP-1] with a detection limit of 0.5 μmol L[SUP-1] at a sampling rate of 90 h[SUP-1]. The simplicity and rapidity of the FIA-EC method used, its reproducibility and sensitivity make it suitable for quality control of pharmaceutical preparations of apomorphine intended for clinical use and research. [ABSTRACT FROM AUTHOR]

Two analytical methods for the quality control of dihydrocodeine in commercial pharmaceutical formulations have been developed and compared with reference methods: a square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC). The electrochemical methods proposed were successfully applied to the determination of dihydrocodeine in pharmaceutical tablets and in oral solutions. These methods do not require any pretreatment of the samples, the formulation only being dissolved in a suitable electrolyte. Validation of the methods showed it to be precise, accurate and linear over the concentration range of analysis. The automatic procedure based on a flow injection analysis manifold allows a sampling rate of 115 determinations per hour. [ABSTRACT FROM AUTHOR]

A square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen, guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L-1 and a linear calibration range from 40 to 140 µmol L-1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L-1 with a detection limit of 3 µmol L-1 and the FIA-EC system allowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%. [ABSTRACT FROM AUTHOR]