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The great interest in the study of antioxidants is mainly the prevention of physiological damage caused by oxidative processes. Cinnamon (Cinnamomum sp.), is a spice used worldwide in cooking and has gained prominence for its pharmacological properties, such as anti-inflamatory, antibacterial, antifungal, cardiovascular, among others. Given the importance of determining the antioxidant capacity in relation to therapeutic methods, this study aims to evaluate the antioxidant profile of commercial cinnamon samples by spectrophotometric, electrochemical and vasorelaxant methods. The spectrophotometric methods performed were 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Folin-Ciocalteu. For the electrochemical experiments, a three-electrode system was used, consisting of carbon paste electrode, platinum wire, and Ag/AgCl/KClsat, representing the working, auxiliary, and reference electrodes, respectively. The electroanalytical methods used were differential pulse, square wave, and cyclic voltammetries. Vascular reactivity was evaluated in aortic artery rings from male Wistar rats, using arteries with intact vascular endothelium and without endothelium. The endothelial nitric oxide synthase (eNOS) pathway and the inhibitor N-nitro-L-arginine-methylester (L-NAME) were used in this analysis. The correlation between the electrochemical approach and total phenols by the ABTS, DPPH, and Folin- Ciocalceu methods were 0.63, 0.70, and 0.73, respectively, with 1 being an ideal correlation. The correlation between spectrophotometric methods was 0.83. For the electrochemical results, a similar profile was observed, with anodic peak a.c Epa1= 0.1 V, indicative of polyphenolic compounds with high antioxidant power. In addition, a biosensor on a carbon paste electrode was applied to the selected extracts using laccase enzyme, obtained by the fungus Marasmiellus sp. and a signal improvement of up to 4 times in the antioxidant profile was observed when compared to the electrode without modification. The samples were analyzed by mass spectrometer, and the main chemical markers found were coumarin, cinnamaldehyde, and eugenol. Pharmacological assays showed that these samples also promoted a significant vasorelaxant effect associated to the antioxidant potential. Thus, cinnamon showed a high antioxidant capacity, in agreement with the results obtained in other studies, emphasizing its importance as a functional food.

Introduction: The pharmaceutical industry faces a major challenge to improve the solubility of some active ingredients. Carvedilol (CRV) is the drug of therapeutic choice in cardiovascular diseases. CRV presents low water solubility and low bioavaliability. Several researches were performed in order to increase the oral bioavailability, where selfemulsifying appeared as viable alternatives. Objective: The objective of this work was to evaluate interactions between CRV and its excipients, detecting the oxidative potential of these substances, thus, providing predictive data for the oxidation that may affect the stability and bioavailability of the drug system. Methodology: In the carbon pastes preparation were used 70 mg (graphite) and 30 mg (oil). Six excipients, oleic acid, canola, capmul, safflower, sesame and Plurol isoestearique. The following proportions were used in the making of the paste: 30:0, 20:10, 15:15, 10:20 and 0:30 of liquid excipient (sample): mineral oil (mg:mg) and 1.5:68.5, 3:67 and 7:63 of solid excipient (sample): graphite (mg:mg). CRV was incorporated in the oil moiety for solubilization and after used in solidstate analysis in the carbon paste. The techniques used were cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Results and Discussions: The Isostearique Plurol® was found to be electro-active in the studied potential, however, this oil oxidizes in different potentials from CRV. The results show that Isostearique Plurol®, liquid excipient, isoestearique acid and the solid excipient presented the greatest variations of anodic potential and were considered the best excipients for the CRV formulation. CRV presented higher stability at room temperature (25 ºC), whereas, it presented higher stability at 50 ºC when mixed with 7% estearique acid. Conclusions: Evidences of incompatibility were not found, relative to the increase of oxidation vulnerability, when in the presence of these excipients. The employment of electroanalysis for CRV compatibility studies show promising viability.

Piroxicam (PRX) was determined in pharmaceutical capsules with differential pulse voltammetry (DPV) in a three electrode system consisting of a pencil graphite electrode (PGE) as working electrode, a Pt wire and a reference electrode of Ag/AgCl/KCl 3 M. An irreversible oxidation peak was observed in Epa c.a. 0.6 V, which correlates to the oxidation of PRX. The coefficient of linear correlation obtained was 0.9946, with limit of detection of 2.1 µM and limit of quantification of 4.7 µM. PGE assays showed good analytical performance compared to high performance liquid chromatography and spectrophotometry, showing the potential to be further developed and employed in quick and simple analyses.

Direct electrochemical reduction of CO2 is a process that could contribute to the reduction of the emission of greenhouse gases by using CO2 as a raw material for fuel production. This paper focuses on voltammetric studies of functionalized electrodes for the electrochemical conversion of CO2 and reports on its use as a tool for electrode screening and optimization. Nickel substrates modified with copper and ruthenium/copper electrodeposits were studied. Voltammetric experiments indicate that CO2 electroreduction follows a nickel type mechanism in which this electrochemical reaction occurs simultaneously and in competition with hydrogen evolution. A significant inhibition of hydrogen evolution reaction is observed in nickel modified electrodes. Inhibition characteristics and the onset of carbon dioxide conversion are dependent of the type of electrode functionalization. Voltammetry is thus a powerful tool to evaluate electrode modifications and for tuning electrodes for an optimized electrocatalytic performance.

The electrochemical behaviour of 2,8-dihydroxyadenine (2,8-DHA)- the main adenine oxidation product- has been investigated over a wide pH range at a glassy carbon electrode (GCE) using cyclic, differential pulse and square wave voltammetry.

Mitoxantrone is an anthracycline used as an antitumour antibiotic for leukaemia and breast cancer treatment, due to its interaction with DNA. However, the molecular mechanism of the antitumour action is not completely understood. Using a glassy carbon electrode the electrochemical oxidation of mitoxantrone was shown to be a complex, pH-dependent, irreversible electrode process involving several metabolites. Comparison of the electrochemical oxidation behaviour of mitoxantrone, ametantrone and aminantrone enabled a deeper understanding of the mechanism and showed the relevance of electrochemical data for the understanding of the cytotoxicity of mitoxantrone. Since mitoxantrone and its oxidation products adsorb strongly on the electrode surface, causing severe problems of electrode fouling, reproducible electroanalytical determinations could only be done at very low concentrations and in an aqueous buffer supporting electrolyte containing 30% ethanol. The detection limit obtained was 10-7 M.

The electrochemical oxidation of 8-oxoguanine (8-oxoG) in the presence of uric acid (UA) was studied by differential pulse voltammetry over a wide pH range (1-12). The results showed that both compounds follow a pH-dependent oxidation mechanism that involves two electrons and two protons corresponding to reversible charge transfer reactions. The difference between the peak potential for the oxidation of each analyte was found to be always less than 100 mV over the whole pH range, the separation being greater in the pH interval 4-7. In mixtures of both analytes, pH 6 was shown to be the best for 8-oxoG determination in the presence of uric acid, since the peak current is higher and a greater peak separation is achieved.

The surface of an electrochemical glassy carbon electrode was modified with a layer of double-stranded DNA (dsDNA) or with double-stranded DNA conditioned in single-stranded DNA (ssDNA) and was used to investigate mitoxantrone-DNA interactions. Differential pulse and square wave voltammetry were applied to develop an electroanalytical procedure for the determination of mitoxantrone and evaluate its interaction with dsDNA or ssDNA immobilized on the electrode surface. The results demonstrate that MTX interaction with DNA is not specific to either guanine or adenine bases. The kinetics of the mitoxantrone-DNA interaction is slow and damage to DNA was followed with time.

Complexes between short oligodeoxynucleotides (ODN) with a variable dGxdCy base composition and liposomes composed of the cationic lipid DOTAP (ODN lipoplexes) were studied by differential pulse voltammetry at a glassy carbon electrode. Since lipoplexes are spontaneously formed by electrostatic interactions, the objective of the voltammetric study was to investigate their behaviour at the electrode surface/solution interface. It was verified that the peak current in the voltammograms for ODN lipoplexes was due to guanosine oxidation and that it was influenced both by the applied adsorption potential and the lipoplex (±) charge ratio used. It was found that for low ODN lipoplexes (±) charge ratios the peak current obtained was enhanced when compared to that registered with free ODN for the same concentration. This allowed a higher sensitivity in the determination of ODN by differential pulse voltammetry and a limit of detection of 5.5 ng/mL was achieved. A model that explains the organisation of ODN lipoplexes at the electrode surface/solution interface is proposed. The electrochemical results presented account for a better physicochemical characterisation of lipoplexes at charged interfaces, which can be important for the understanding and development of gene therapy vectors based on ODN lipoplexes.