Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> http://www.scielo.br/rss.php?pid=0103-505320150004&lang=es vol. 26 num. 4 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Novel <em>N</em>-Acylated Benzimidazolone Derivatives: Synthesis, 2D-QSAR and Targets Prediction]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400633&lng=es&nrm=iso&tlng=es A series of novel N-acylated benzimidazolone derivatives, were synthesized from 4-aminobenzoic acid, and their antifungal activities against Botrytis cinerea were evaluated by spore germination assay. Preliminary results indicated that most of the benzimidazolone derivatives had inhibitory effect on spore germination, among which 6-carboxylate substituted derivatives were more effective than its 5-substituted regioisomers. Furthermore, 2D-quantitative structure-activity relationship (2D-QSAR) studies revealed good predictive and statistically significant QSAR models, as well as highlighted that the activities were strongly influenced by the type of introduced acyl groups in the benzimidazolone moiety. Potential targets of the title compounds were predicted using ligand profiling and validated by molecular docking, and the results implied that the title compounds might be a new type of fatty acid synthetase inhibitor. <![CDATA[Fast Classification of Different Oils and Routes Used in Biodiesel Production Using Mid Infrared Spectroscopy and PLS2-DA]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400642&lng=es&nrm=iso&tlng=es This work aimed at employing partial least square discriminant analysis (PLS2-DA), allied to mid-infrared (MIR) spectroscopy as an analytical method for simultaneous classification of biodiesels from different oils (soybean and used frying oil) and routes (methylic and ethylic). The evaluation of the model was verified through values of sensitivity and specificity for each parameter, in the interest class. PLS2-DA model showed 100% correct classification in the discrimination of types of biodiesels. Therefore, the proposed methodology is fast, because it allows simultaneous classification of different types of biodiesels. Consequently, it can be used in quality control of this type of biofuel. <![CDATA[HPLC-DAD and UV-Vis Spectrophotometric Methods for Methotrexate Assay in Different Biodegradable Microparticles]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400649&lng=es&nrm=iso&tlng=es The challenge of the present work concerned the development and validation of high performance liquid chromatography (HPLC) and UV-Vis spectrophotometric methods for quantitation of methotrexate (MTX) loaded on biodegradable microparticles, composed of copolymers with different solubilities such as chitosan and poly (lactic-co-glycolic acid) (PLGA). The linearity of the analytical curves for MTX were &gt; 0.999 (r2) and the limits of detection (LOD) were 0.014 µg mL-1 and 0.060 µg mL-1 for HPLC and UV-Vis spectrophotometric method, respectively. In addition, both methods were specific, robust, and accurate with a recovery between 89.5% and 105.5%. The method showed precision with relative standard deviations lower than 3.39% for HPLC and 2.90% for UV-Vis spectrophotometry. Statistical analysis revealed that both methods provide equivalent results, and also can be used for quality control of MTX-loaded in drug delivery systems. <![CDATA[Main Degradation Products of Dabigatran Etexilate Evaluated by LC-UV and LC-ESI-MS, Degradation Kinetics and in vitro Cytotoxicity Studies]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400660&lng=es&nrm=iso&tlng=es The present study reports the stability profile of an antithrombotic drug: dabigatran etexilate (DAB). The drug was subjected to thermal degradation at 60 ºC and products formed were investigated by liquid chromatography-UV (LC-UV) and liquid chromatography-mass spectrometry (LC-ESI-MS). Chromatographic separation of the degradation products was performed on a GL Sciences Inc. Inertsil ODS-2 column (250 mm × 4.6 mm i.d., with a particle size of 5 µm and pore size of 110 Å) with mobile phase consisting of acetonitrile and ammonium acetate buffer (pH 5.5; 10 mmol L−1) (65:35, v/v) pumped at 1.0 mL min−1 flow rate. Column temperature was set at 30 ºC and detection at 225 nm using a UV detector. LC-UV method previously validated was extended to LC-ESI-MS for the characterization of the degradation products (DP-01 and DP-02) formed, without complicated isolation or purification processes, based on retention times and confirmation of molecular weight. Degradation kinetics of DAB was also evaluated and could be described as a first-order process (R2= 0.9900). Furthermore, no evidence of cytotoxicity in human mononuclear cells was observed for DAB degraded samples. <![CDATA[Visualisation of the Galvanic Effects at Welds on Carbon Steel]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400667&lng=es&nrm=iso&tlng=es Non-destructive classical techniques, such as electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurement, were complemented with advanced techniques, including the scanning vibrating electrode technique (SVET) and localised electrochemical impedance spectroscopy (LEIS) to examine galvanic effects at welds on carbon steel. The classical techniques indicated that corrosion processes are accelerated in the weld. The advanced techniques revealed admittance values related to more severe corrosion along the weld than in the base metal and higher corrosion currents in the weld. When the weld and base metal are electrically connected, the weld serves as a cathodic protector for the base metal. <![CDATA[Application of Headspace Solid-Phase Microextraction and Gas Chromatography- Mass Spectrometry (HS-SPME-GC/MS) on the Evaluation of Degradation Efficiency of Phenolic Compounds and Identification of By-Products from Produced Water]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400676&lng=es&nrm=iso&tlng=es Application of the headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC/MS) technique as an analytical tool to monitoring the degradation of phenolic compounds and the formation of by-products in produced water by UV photolysis and UV/peroxide is proposed. All of the experimental conditions for the degradation tests were carried out according to the response of the surface modeling methods developed. The direct photolysis and the UV/H2O2 processes were capable to degrade more than 99% of the initial concentrations of total phenolic components of produced water. The main by-product found was 2,6-di-tert-butylbenzoquinone (DBQ). The presence of DBQ and other hydroxy compounds, constituting the major fraction of by-products identified, demonstrates that the degradations are initiated by the oxidation of the aromatic phenolic ring generating quinones, diphenols, benzoic acids and phenones. <![CDATA[Ozone Treatment for the Removal of Residual Chlorothalonil and Effects on the Quality of Table Grapes]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400687&lng=es&nrm=iso&tlng=es Due to uncontrolled use of pesticides and disregard for harvest intervals, some pesticide residue is present in various foods. Treatments using ozone as an alternative for food decontamination have been studied in recent years due to ozone’s high oxidation potential even at low concentrations. The present work aimed to evaluate chlorothalonil removal from table grapes by the immersion of fruit in distilled water continuously bubbled with ozone gas. This strategy allowed the removal of 60% of chlorothalonil from table grapes (pulp and skin), regardless of ozone concentration. Ozone treatment of table grapes at a gas concentration of 3 mg L−1 changed most of the quality parameters evaluated. Treatment at 2 mg L−1 maintained the fruit quality for a longer storage period compared to the untreated control table grapes. <![CDATA[CO Oxidation Catalyzed by Ag Nanoparticles Supported on SnO/CeO<sub>2</sub>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400695&lng=es&nrm=iso&tlng=es Ag-Sn/CeO2 catalysts were synthesized by the co-precipitation method with different Ag-Sn wt.% loadings and were tested for the oxidation of CO. The catalysts were characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED) techniques. UV-Vis measurements were carried out to elucidate the ionic states of the silver particles, and the temperature-programmed reduction (TPR) technique was employed to check the reduction temperature of the catalyst supported on CeO2. There are peaks for silver crystallites in the X-ray diffraction patterns and the presence of SnO was not well evidenced by the XRD technique due to sintering inside the 3D array channels of CeO2 during the calcination process. The Ag-Sn/CeO2 (4%) catalyst was the most efficient and exhibited 100% CO oxidation at 100 ºC due to small particle size and strong electronic interaction with the SnO/CeO2 support. <![CDATA[Can Ergosterol Be an Indicator of <em>Fusarium</em> Fungi and Mycotoxins in Cereal Products?]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400705&lng=es&nrm=iso&tlng=es Presence of fungi in food and feed products is a major problem. Fungi synthesize a large number of secondary metabolites including particularly harmful mycotoxins. They can be produced in plant tissues and are commonly found all over the world in many products including cereals. A total of 44 samples were taken for identification of ergosterol - the potential marker of fungal presence. Fourteen of these samples were chosen for further studies that included the evaluation of the relationship between ergosterol content and three major mycotoxins produced by Fusariumspp.: fumonisin B1, zearalenone and deoxynivalenol. Fungal strains were also isolated and identified by molecular means in those samples. The results of the studies give a further and more detailed insight into the relationship between contents of ergosterol and mycotoxins in different cereal products. It was found that there was no correlation between content of ergosterol and mycotoxins in the tested food products. Also, the presence of mycotoxins was not correlated with occurrence of species able to produce these toxins. <![CDATA[Simultaneous Determination of Ascorbic Acid, L-Dopa, Uric Acid, Insulin, and Acetylsalicylic Acid on Reactive Blue 19 and Multi-Wall Carbon Nanotube Modified Glassy Carbon Electrode]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400713&lng=es&nrm=iso&tlng=es A trifunctional electrochemical sensor was fabricated for simultaneous determination of ascorbic acid (AA), levodopa (LD), and insulin. This was done by modifying a glassy carbon electrode (GCE) with multi-walled carbon nanotubes and reactive blue 19 (RB-MWCNT-GCE). Cyclic voltammetry was used to investigate the redox properties of this modified electrode. The electro-catalytic activity of the modified electrode was studied for the oxidation of AA, LD, and insulin. By differential pulse voltammetry (DPV), the detection limits of AA, LD, and insulin were estimated to be 0.45 µmol L -1, 0.37 µmol L-1, and 0.25 µmol L-1, respectively. In DPV measurements, the RB-MWCNT-GCE could separate the oxidation peak potentials of AA, LD, uric acid (UA), insulin, and acetylsalicylic acid (ASA) in a mixture. The practical utility of this modified electrode was demonstrated by detecting AA, LD, UA, insulin, and ASA in real samples. <![CDATA[Virginicin, a New Naphthalene from <em>Kosteletzkya virginica</em> (Malvaceae)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400723&lng=es&nrm=iso&tlng=es A new naphthalene, 8-methoxy-2,7-dihydroxyl-4-(1'-hydroxyl-isopropyl)-6-methyl-1-naphthaldehyde, together with twelve known compounds were isolated from the tubers of Kosteletzkya virginica. Their structures were elucidated by spectroscopic methods, including 1D-, 2D-nuclear magnetic resonance (NMR) and high-resolution time of flight electrospray ionization mass spectrometry (HRTOFESIMS). Some compounds were evaluated for their potential in scavenging diphenyl-picryl hydrazyl radical (DPPH•), inhibition of nitric oxide (NO) induced by lipopolysaccharide (LPS), and cytotoxic activity. The new compound showed activities against DPPH•, NO, human acute promyelocytic leukemia (HL-60) and human colorectal adenocarcinoma (LOVO), with IC50 of 34.6, 12.5, 40.5, 31.7 μmol L-1 respectively. <![CDATA[Development and Validation of a Dissolution Test Method for Albendazole and Praziquantel in Their Combined Dosage Form]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400729&lng=es&nrm=iso&tlng=es A dissolution test method and an analytical procedure by HPLC were developed and validated for the evaluation of the dissolution of tablets containing albendazole and praziquantel. Two different commercially tablets containing 500 mg of albendazole and 50 mg of praziquantel for veterinary use were selected for this study. A dissolution medium containing a mixture of 300 mL ethanol and 600 mL of 0.1 mol L-1 HCl was found suitable to ensure sink conditions. USP Apparatus 2, 900 mL dissolution medium and 75 rpm were fixed. Dissolution profiles were generated at 45 min. Dissolution samples were analyzed with a reversed-phase high-performance liquid chromatography (RP-HPLC) method with ultraviolet (UV) detection at 210 nm, developed and validated for this purpose. Each product was also assayed for analyte content according to USP 35. The dissolution test described here could be proposed as a means of assessing finished product quality. <![CDATA[Cytotoxic Chalcones from <em>Desmodium oxyphyllum</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400736&lng=es&nrm=iso&tlng=es Three new chalcones were isolated from Desmodium oxyphyllum. Their structures were elucidated by spectroscopic methods including extensive 1D- and 2D-nuclear magnetic ressonance techniques. The compounds were evaluated for their cytotoxicity against five human tumor cell lines (NB4, A549, SHSY5Y, PC3, and MCF7). The results showed that the compounds exhibited weak cytotoxicity against some selected cell lines with IC50 values ranging from 3.6 to 8.9 μM. <![CDATA[Selective Determination of 2,4,6-Trinitrotoluene in Water Samples Based on Magnetic Imprinted Nanoparticles via Grafting Polymerization]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400741&lng=es&nrm=iso&tlng=es The magnetic surface imprinted polymer was effectively synthesized based on grafting polymerization for selective determination of 2,4,6-trinitrotoluene (TNT) as template molecule. The "grafting to" procedure was performed by copolymerizing of vinyl modified magnetic substrate with methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linking agent, respectively. The morphology, structure and polymeric properties of imprinting polymers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transforms infrared spectroscopy (FT-IR). In order to improve on the adsorption capacity amount, the various parameters were considered. The resulting sorbent exhibited a high capacity with appropriate selectivity for TNT molecules. The evaluation demonstrated a linear range of 10-500 µg L−1 with the detection limit of 3.0 µg L−1. Moreover, the performance of the present sorbent was studied for extraction and determination of TNT compound in environmental waters and acceptable recoveries ranging from 91.7 to 100.8% were achieved. <![CDATA[Agarose-Alumina Composite Supported Palladium Catalyst for Suzuki Coupling Reactions]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400748&lng=es&nrm=iso&tlng=es The palladium catalyst supported on agarose-alumina composite and its utilization in the Suzuki reaction have been investigated. The agarose-alumina composite was prepared and modified with organofunctional groups by reacting with the coupling reagent 3-aminopropyltriethoxysilane (APTES) through Al−O−Si bonds. Palladium was efficiently loaded on the composite by the amino groups. The Suzuki coupling reaction can proceed successfully at room temperature under air. High yields of various aryl-aryl products have been obtained. Recycling studies have shown that the catalyst can be easily recovered and reused several times. The yields decreased from 95% to 85% in five cycles. <![CDATA[Molecular Sieves Mediated Green Per-<em>O</em>-Acetylation of Carbohydrate Templates and Lipase Catalyzed Regioselective Alcoholysis of 2,3,5-Tri-<em>O</em>-Acetyl-D-Ribonolactone]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400755&lng=es&nrm=iso&tlng=es The per-O-acetylation of D-ribono-1,4-lactone and representative carbohydrates through the combination of acetic anhydride and molecular sieves under solvent-free conditions is demonstrated. The use of 13X/KCl molecular sieves as the heterogeneous catalyst was found to be more efficient than the excess of pyridine normally employed in the conventional method, giving high yields of the expected peracetylated product after 3 h at 25 ºC or 1 h at 50 ºC. The transformation can be carried out in gram scale and in an open flask. Additionally, the catalyst is readily separated from the reaction medium and can be reutilized without significant loss of activity. This green procedure for acetylation was extended to D-ribonolactone derivatives and natural carbohydrates. To demonstrate the synthetic utility of the method, 2,3,5-tri-O-acetyl-D-ribonolactone was selected as the substrate for the regioselective alcoholysis of acetyl group catalyzed by Candida antarctica lipase B in EtOH to selectively produce 2,3-di-O-acetyl-D-ribonolactone in gram scale. <![CDATA[Synthesis of Biphenyl Tyrosine Via Cross-Coupling Suzuki-Miyaura Reaction Using Aryltrifluoroborate Salts]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400765&lng=es&nrm=iso&tlng=es We reported a fast and easy method for obtaining biarylic units from tyrosine derivatives via Suzuki-Miyaura cross-coupling using a variety of substituted and unsubstituted potassium aryl- and heteroaryltrifluoroborate salts. The scope of the methodology was also extended to the formation of bis-tyrosine linked dipeptide bonds, leading to biologically interesting compounds. Some biarylic units were obtained as free amino acids through the one step cleavage reaction in good yields. <![CDATA[Performance Evaluation of a Portable Laser-Induced Fluorescence Spectroscopy System for the Assessment of the Humification Degree of the Soil Organic Matter]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400775&lng=es&nrm=iso&tlng=es Laser-induced fluorescence spectroscopy (LIFS) has shown advantages for analyses of whole soil, providing results about chemical structure of soil organic matter (SOM) without the need for a chemical fractionating process; thus, allowing direct analysis of soils. Moreover, another advantage is the potential for the development of portable systems, which could be usable in field analyses. The aim of this paper is to evaluate the performance of a portable LIFS system to assess the humification degree (HD) of SOM. A good correlation (R &gt; 0.8) was obtained for results (HD) achieved using the proposed portable system and a conventional fluorescence spectrometric method for humic acid. In addition, the results obtained using the portable LIFS system statistically agreed with the ones achieved using a benchtop LIFS system already described in the literature for such application (R = 0.953). Thus, the portable LIFS system constitutes an affordable option for the in situ characterization of SOM. <![CDATA[(1<em>R,</em>2<em>S,</em>6<em>R</em>)-Papayanol, Aggregation Pheromone of the Guava Weevil, <em>Conotrachelus psidii</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400784&lng=es&nrm=iso&tlng=es Comparative GC/MS analysis of airborne volatiles produced by males and females of the guava weevil Conotrachelus psidii (Coleoptera: Curculionidae: Molytinae) showed the presence of a malespecific electroantennographically active compound identified as (1R,2S,6R)-2-hydroxymethyl-2,6- dimethyl-3-oxabicyclo[4.2.0]octane (papayanol). Release of this compound was dependent on the photoperiod, taking place primarily during the scotophase, with a maximum release between 2 and 6 h after the onset of the scotophase. Y-tube olfactometer bioassays revealed a strong attractiveness of the papayanol to male and female weevils considering the presence of the plant volatiles. <![CDATA[Kinetics and Product Analysis of the Electrochemical Dehalogenation of Hexachlorobenzene]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400790&lng=es&nrm=iso&tlng=es A method for establishing the kinetics and products of the electrochemical degradation of hexachlorobenzene (HCB) is described. One plausible way of reducing HCB´s toxicity is through cathodic dehalogenation. The characterization of products formed during the electrochemical reduction and the reaction kinetics are both reported. Pentachlorobenzene (PCB), tetrachlorobenzene (TCB) and trichlorobenzene (TriCB) were identified among the degradation products by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The kinetics is analyzed under different electrolysis conditions. <![CDATA[Validation of a High Performance Liquid Chromatography Method for Aflatoxins Determination in Corn Arepas]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400797&lng=es&nrm=iso&tlng=es Aflatoxins are toxic metabolites produced by Aspergillus species in raw materials and foodstuffs from agricultural sources. Due to the fact that aflatoxins are potentially carcinogenetic, it is important to have reliable analytic methods that allow determining their levels in food matrices. The main aim of this investigation was to validate the method for aflatoxins determination by high performance liquid chromatography in corn arepas, which are widely consumed in the Colombian coffee region. The evaluated parameters were robustness, selectivity, linearity, sensitivity, repeatability, intermediate precision and recovery. The methodology was successfully validated with and optimal selectivity, linearity &gt; 0.9998, limits of detection and quantification lower than 0.10 μg kg−1, relative standard deviation &lt; 4.5% and recovery &gt; 76.6%. Also, 144 corn arepas samples were analyzed and aflatoxins were found in 9.72% of them, with levels between 0.95 and 11.56 μg kg−1. <![CDATA[Caesalpinioflavone, a New Cytotoxic Biflavonoid Isolated from <em>Caesalpinia pluviosa var. peltophoroides</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400804&lng=es&nrm=iso&tlng=es The present study aimed to investigate the presence of compounds with antitumor activity in the plant Caesalpinia pluviosa var. peltophoroides. From bioactivity guided studies it was possible to isolate a new biflavonoid, named caesalpinioflavone, whose chemical structure was determined by spectroscopic (1H and 13C nucler magnetic ressonace, homonuclear correlation spectroscopy and heteronuclear multiple-bond correlation spectroscopy) and spectrometric (high resolution electrospray ionization mass) methods. According to in vitro assays, caesalpinioflavone was effective in reducing the cell viability of tumor cell lines A549, MCF7, Hst578T and HTC. This effect was consequent of cell cycle arrest in G1/S transition (A549 and MCF7) and cytotoxic activity (Hs578T and HTC). Taken together, these data indicate that caesalpinioflavone has a promising antitumor activity. <![CDATA[Synthesis of Alkylseleno-Carbohydrates and Evaluation of their Antioxidant Properties]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400810&lng=es&nrm=iso&tlng=es In the present study, we describe the synthesis of alkylseleno carbohydrates with different sugar scaffolds and the evaluation of their antioxidant activity profile. A compound possessing a C8 alkyl chain presented the best results in the free radical scavenging activity. <![CDATA[A New Straightforward Synthesis of 2', 3'-Didehydro-2', 3'-dideoxy-2'-(2"- (trimethylsilyl)ethylthio)thymidine, Key Intermediate for the Synthesis of 2'-Substituted Thionucleosides]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400816&lng=es&nrm=iso&tlng=es We describe herein a straightforward and efficient preparation of 2',3'-dideoxy-2'-(2''- (trimethylsilyl)ethylthio)thymidine, which allows the preparation of diverse potentially antiviral and/or anticancer nucleosides (disulfides, thiols, sulfides, thiocyanates). <![CDATA[Collision-Induced Dissociation Analysis of Brevianamide A and C in Electrospray Ionization Mass Spectrometry]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400822&lng=es&nrm=iso&tlng=es Brevianamides A and C are isomeric cyclic peptides with several reported biological activities, isolated from diverse microorganisms. Currently, there has been no previous investigation of brevianamide fragmentation utilizing electrospray ionization mass spectrometry (ESI-MS). In this work experiments were carried out in the positive mode using two different spectrometers (low and high resolution) with an ESI source. Computational chemistry studies helped identify the protonation sites based upon atomic charges, proton affinities and molecular orbitals, computed using the B3LYP/6-31++G (d,p) model. The data suggests that the presence of the allylic position of the lactamic N in brevianamides C governs its fragmentation pathways. Distinguishing between brevianamides A and C using positive ion electrospray tandem mass spectrometry (ESI(+)MS/MS) is made possible by the spectral difference of each isomer and offers an alternative to other spectroscopic techniques. <![CDATA[Additions and Corrections]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400828&lng=es&nrm=iso&tlng=es Brevianamides A and C are isomeric cyclic peptides with several reported biological activities, isolated from diverse microorganisms. Currently, there has been no previous investigation of brevianamide fragmentation utilizing electrospray ionization mass spectrometry (ESI-MS). In this work experiments were carried out in the positive mode using two different spectrometers (low and high resolution) with an ESI source. Computational chemistry studies helped identify the protonation sites based upon atomic charges, proton affinities and molecular orbitals, computed using the B3LYP/6-31++G (d,p) model. The data suggests that the presence of the allylic position of the lactamic N in brevianamides C governs its fragmentation pathways. Distinguishing between brevianamides A and C using positive ion electrospray tandem mass spectrometry (ESI(+)MS/MS) is made possible by the spectral difference of each isomer and offers an alternative to other spectroscopic techniques. <![CDATA[Additions and Corrections]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000400829&lng=es&nrm=iso&tlng=es Brevianamides A and C are isomeric cyclic peptides with several reported biological activities, isolated from diverse microorganisms. Currently, there has been no previous investigation of brevianamide fragmentation utilizing electrospray ionization mass spectrometry (ESI-MS). In this work experiments were carried out in the positive mode using two different spectrometers (low and high resolution) with an ESI source. Computational chemistry studies helped identify the protonation sites based upon atomic charges, proton affinities and molecular orbitals, computed using the B3LYP/6-31++G (d,p) model. The data suggests that the presence of the allylic position of the lactamic N in brevianamides C governs its fragmentation pathways. Distinguishing between brevianamides A and C using positive ion electrospray tandem mass spectrometry (ESI(+)MS/MS) is made possible by the spectral difference of each isomer and offers an alternative to other spectroscopic techniques.