Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> vol. 28 num. 6 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Silver and Silver Chloride Nanoparticles and their Anti-Tick Activity: a Mini Review]]> This overview highlights the importance of characterization of biogenic nanoparticles of silver and silver chloride in order to understand the action on ticks or pathogens transmitted by them. These nanoparticles appear as important active principles in this area. They can act against ticks or against major pathogens transmitted by the bite of ticks such as bacteria, viruses or protozoa with equal or better efficacy of antibiotics, antiviral or antiparasitic agents. Anti-tick activities on Rhipicephalus (Boophilus) microplus, Hyalomma anatolicum, Hyalomma isaaci and Haemaphysalis bispinosa are discussed. Perspectives of these nanoparticles acting on bacteria, viruses and protozoa infections are also discussed. <![CDATA[The Chemistry of the Sesquiterpene Alkaloids]]> We present the occurrence, structures, biological activities, biosynthesis, and syntheses of the sesquiterpene alkaloids. <![CDATA[Calcium Phosphate Coatings by Sol-Gel on Acrylonitrile-butadiene-styrene Substrate]]> Additive manufacture is an effective technology to produce complex macrostructures from polymers. Sol-gel is a chemical process that affords multifunctional materials by functionalization of different substrates. This work reports on the use of acrylonitrile-butadiene-styrene polymer (ABS) as starting material to obtain a substrate by additive manufacture. Coating of ABS by the sol-gel methodology generated a multifunctional material. Sols with and without phosphate ions were prepared from silicon and calcium alkoxide. Based on X-ray diffraction patterns, a calcium phosphate crystalline structure emerged on ABS after contact of the substrate with simulated body fluid. Infrared analysis revealed that the peaks of the functionalized substrate shifted, indicating that ABS interacted with the sol-gel coating. According to thermal analysis, the maximum decomposition temperature of the coated samples was 20 ºC higher as compared to non-coated ABS. Sol-gel and additive manufacture are important technologies to produce materials with applications in biological medium. <![CDATA[A Simple and Fast Method for Magnetic Solid Phase Extraction of Ochratoxin A]]> We report on the synthesis of dopamine loaded magnetic nanoparticles (MNPs) for new, simple, fast and repeatable extraction of ochratoxin A from different solvents and milk without utilizing immunoaffinity columns and even high-tech devices. To this end, Fe3O4 nanoparticles (NPs) were synthesized using thermal decomposition reaction and dopamine (DPA) was then conjugated with Fe3O4 nanoparticles (NPs) to form Fe3O4-DPA NPs. Dynamic light scattering, field emission scanning electron microscopy and transmission electron microscopy revealed an average size of about 15 nm for Fe3O4-DPA NPs. Moreover, zeta potential measurement and vibrating sample magnetometer confirmed positively charged (16.8 mV) and superparamagnetic behavior of MNPs, which are effective factors for a good adsorbent in the extraction. Various solvents and different effective parameters were measured until acetonitrile:methanol was selected as the best extraction solvent. In addition, based on the pH-partition theory, with changes in pH, we were able to increase and enhance the extraction rate to 94%. Moreover, the ability of Fe3O4-DPA NPs in solid phase extraction of ochratoxin A from spiked milk was evaluated. The recovery rate for extraction of OTA from milk was 68%. <![CDATA[Laccase-Assisted Rapid Synthesis of Colloidal Gold Nanoparticles for the Catalytic Reduction of 4-Nitrophenol]]> A green method for the rapid preparation of uniform-sized colloidal gold nanoparticles under ambient conditions was presented and validated using laccase as a reduction agent in alkaline medium. UV-Vis spectrophotometry, field-emission high-resolution transmission electron microscopy, X-ray diffraction, selected area electron diffraction, energy dispersive X-ray analysis, zetasizer, and Fourier transform infrared spectroscopy were used to characterize the gold nanoparticles. The gold nanoparticles were spherical, crystalline, uniform, and monodisperse with an average size of 12.24 nm. These nanoparticles were successfully used to reduce 4-nitrophenol in the presence of NaBH4 and exhibited an excellent catalytic activity. <![CDATA[In Tube Ultrasonic and Air Assisted Liquid-Liquid Microextraction-Gas Chromatography-Mass Spectrometry Determination: a Novel Method for the Determination of Phthalate Esters in Aqueous Samples]]> In this study, a highly sensitive and reliable microextraction method, known as in tube ultrasonic and air assisted liquid-liquid microextraction (IT-UAA-LLME), was developed for the preconcentration of some phthalate esters, such as dimethyl phthalate, diethyl phthalate (DEP), di-butyl-phthalate (DBP), bis(2-ethylhexyl) phthalate (BEHP), butyl benzyl phthalate (BBP), and di n-octyl-phthalate (DNOP), prior to their determination using gas chromatography-mass spectrometry (GC-MS). In this technique, the extraction solvent was dispersed into the aqueous sample solution using an ultrasonic bath. The effects of solvent type, aeration time and salt concentration were investigated. After extraction, an organic solvent was injected into the GC-MS instrument for quantification. Under optimum conditions, the enrichment factors ranged from 100 to 330. The calibration curves showed good linearity (r2 &gt; 0.99) and limit of detections were obtained in the range of 0.1-2.1 ng mL-1 in the working concentration ranges. The method was successfully applied for determination of six phthalate esters in real samples with complex matrices with relative standard deviation less than 8%, recovery 88-112% and thus, satisfactory results were obtained. <![CDATA[Synthesis, Three-Dimensional Structure, Conformation and Correct Chemical Shift Assignment Determination of Pharmaceutical Molecules by NMR and Molecular Modeling]]> This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. <![CDATA[Isopropyl Octanoate Synthesis Catalyzed by Layered Zinc <em>n</em>-Octanoate]]> Isopropyl octanoate is an ester used in the formulation of cosmetics, foods, medicines, and other products. The peculiar thermodynamic and kinetic factors, allied with the demand for the applications mentioned above, justify the development of an optimized process for its synthesis. In the present article, the esterification of octanoic acid with isopropanol while using zinc n-octanoate as catalyst is reported. A factorial design was employed where variables such as molar ratio (alcohol:acid), percentage of catalyst (in relation to the acid mass) and temperature were investigated. It was observed that zinc octanoate showed promising catalytic activity, especially at 165 °C, with molar ratios of 8:1 and 6:1, and with 7 and 10% of catalyst, where conversions up to 75% were observed. Optimized conditions for the production of isopropyl octanoate were determined to be 165 °C, 6:1 molar ratio and 5.97% of catalyst. <![CDATA[Direct Incorporation of Ginger and Oregano Antioxidants in Canola Oil]]> Antioxidants are used to increase the shelf life of food and oils. The most common extraction method of antioxidants from natural sources is the use of organic solvents, like methanol and ethanol. Evaporation of all the organic solvent is necessary to prevent health diseases. In this study, we present a new "organic solvent-free" method to extract antioxidants, which uses canola oil as extraction solvent to incorporate natural antioxidants from oregano and ginger without the use of organic solvent. The oil solvent extraction capacity was assessed by assays of oxygen radical absorbance capacity method for hydrophilic (721.9 ± 10.5 and 89.0 ± 2.5 µmol TE g-1 to canola oil with oregano and ginger, respectively) and lipophilic (118.8 ± 7.4 and 48.2 ± 9.7 µmol TE g-1 to canola oil with oregano and ginger, respectively) compounds, oxidation test (Oxitest®) (1,434 and 1,018 minutes to canola oil with oregano and ginger, respectively) and thiobarbituric acid reactive substances (0.01 ± 0.02 and 0.11 ± 0.06 mg MA g-1 to canola oil with oregano and ginger, respectively). Results provide evidence of the efficiency of canola oil as antioxidants extractor. Nine antioxidant compounds from canola oil incorporated with antioxidants compounds were identified using high performance liquid chromatography tandem mass spectrometry. <![CDATA[Larvicidal Activity of <em>Beauveria bassiana</em> Extracts against <em>Aedes aegypti</em> and Identification of Beauvericins]]> Beauveria bassiana is an entomopathogenic fungus that has been well known for its capacity to act as biopesticide on various disease vectors. The analysis of organic extracts of strains CG71 and UNI40 led to identification of cyclodepsipeptides beauvericin, beauvericin A or F, beauvericin E and bassianolide by ultra-high pressure liquid chromatography-high resolution mass spectrometry in tandem mode (UHPLC-HRMS/MS). The larvicidal activity on 3rd instar of Aedes aegypti revealed LC50 0.9887 and 0.4653 ppm in 24 and 48 hours (CG71 methanolic extract), LC50 0.7834 ppm in 48 hours (CG71 ethyl acetate), LC50 0.7834 and 1.8149 ppm (UNI 40 for ethyl acetate and methanolic extracts, respectively) in 48 hours. These findings highlight the potential of B. bassiana metabolites for controlling the vector of Dengue and Zika diseases. <![CDATA[Miscellaneous Diterpenes from the Aerial Parts of <em>Plectranthus ornatus</em> Codd]]> Five new diterpenes derivatives named as ornatin A, B, C, D and E, in addition to six known related diterpenes were isolated from the aerial parts of cultivated specimens of Plectranthus ornatus. The structures were elucidated using a combination of 1D/2D nuclear magnetic resonance (NMR) spectroscopy, high-resolution electrospray ionization mass spectrometry (HRESIMS) and comparison with published NMR data of analogous compounds. All isolated compounds were assayed against four human cancer cell lines, and Gram-positive and Gram-negative bacteria strains. None of them showed any cytotoxic activity, but ornatin C, D, E and three related diterpenes displayed marginal bactericidal or bacteriostatic effects against the Gram-positive strains. <![CDATA[First Asymmetric Reduction of Isatin by Marine-Derived Fungi]]> In this study, whole cells of marine-derived fungi were used to reduce isatin (1H-indole-2,3-dione) to dioxindole (3-hydroxyindolin-2-one) for 7 days at 32 °C. The screening showed that several strains could reduce isatin and produce the enantioenriched dioxindole. The best conversions were obtained by Cladosporium sp. CBMAI 1237 and Westerdykella sp. CBMAI 1679, however, the best enantiomeric excess was obtained only by Aspergillus sydowii CBMAI 935 (66% ee). In conclusion, marine-derived fungi show potential for asymmetric and chemoselective reduction of isatin (1H-indole-2,3-dione). <![CDATA[Development of a Dissolution Test for Fenbendazole-Praziquantel Capsules Using UV-PLS Method]]> A dissolution test for capsules containing 50 mg of praziquantel and 500 mg of fenbendazole was developed and validated. The optimal conditions were an USP apparatus 2 with paddles rotating at 75 rpm, 900 mL dissolution medium (a mixture of 300 mL of ethanol and 600 mL 0.5 mol L-1 HCl), at 37.0 ± 0.5 °C. Both analytes achieved with sink conditions. A published high-performance liquid chromatography (HPLC) method was used to monitoring dissolution test during the optimization. Additionally, a chemometrics method based on UV-VIS spectrophotometry and partial least-squares (PLS) was developed and validated for the simultaneous determination of both analytes in the dissolution media. The coefficients of determination were 0.9986 and 0.9959 for fenbendazole and praziquantel, respectively, and the elliptical joint confidence region (EJRC) test concluded that constant and proportional biases were absent. The optimized model was applied to build dissolution profile and its results did not show statistical differences with HPLC method. <![CDATA[Preparative Separation and Structural Identification of Impurities of a New α<sub>2</sub>-Adrenoceptor Agonist Using Stacking Injection, LC-MS<sup>n</sup> and LC-SPE-NMR]]> Identifying impurities in drug substances has become one of the most important issues in pharmaceutical analysis since it can have a significant impact on the efficacy of new pharmaceutical products. Due to the purity requirements, in this paper a new synthetic α2-adrenoceptor agonist, called LPSF-PT-31, was purified and its impurities were characterized by liquid chromatography-multistage mass spectrometry (LC-MSn) and liquid chromatography-solid phase extraction-nuclear magnetic resonance (LC-SPE-NMR). The purification step was conducted using a semi-preparative liquid chromatography and stacked injections as a new approach to drug purification. As a result, a total yield of 75% of the pure LPSF-PT-31 and 2.9 L day-1 in solvent reduction was obtained. The combination of semi-preparative stacking injection, LC-MSn, and LC-SPE-NMR, demonstrated to be efficient to purify active drugs and unambiguously identify its impurities. In addition, isolation and identification of drug impurities in the early stages of development can improve the synthetic pathway, preventing the formation of impurities or minimizing this formation to minimum levels. <![CDATA[Study of Reactions of Two Mannich Bases Derived of 4'-Hydroxychalcones with Glutathione by RP-TLC, RP-HPLC and RP-HPLC-ESI-MS Analysis]]> 4'-Hydroxychalcones have been reported to possess several beneficial biological effects. Several lines of evidence accumulated to demonstrate increased biological activities of the Mannich base derivatives of the parent 4'-hydroxychalcones. Bioactivities of chalcones and related α,β-unsaturated ketones are frequently associated with their reactivity with cellular thiols, such as GSH. For comparison of GSH reactivity, two bis Mannich bases of two 4'-hydroxychalcones were synthesized and reacted with GSH under non-cellular conditions. Reversed-phase thin layer chromatography (RP-TLC) and reversed-phase high performance liquid chromatography (RP-HPLC) analysis showed formation of two polar products which structures were confirmed by RP-HPLC-ESI-MS (RP-HPLC-electrospray ionization mass spectrometry) as 1:1 chalcone-GSH adducts in each case. At pH values below 8.0, the two bis Mannich bases showed higher GSH reactivity than two 4'-hydroxychalcones. Influence of the nature of the amino groups, the ring-B substituents and pH of the medium on reactivity was also investigated. The findings could serve as useful structure-activity information for subsequent molecular modification of thiol-reactive 4'-hydroxychalcones. <![CDATA[Synthesis, Characterization and Dielectric Properties of New 5-(4-Hydroxyphenyl)- 10,15,20-tri-4-[2-(3-pentadecylphenoxy)ethoxy]phenyl porphyrin and Their Ni, Co and Cu Complexes]]> New asymmetric cardanol-based porphyrins, free-base and coordinated with Ni, Co and Cu, were synthesized and completely characterized as A3B type. Such porphyrins were obtained aiming improved solubility in polar solvents due insertion of an -OH phenolic group. Their thermal and dielectric properties were also evaluated. Changes in the synthetic route reduced the reaction time and improved the yields of the aldehyde precursor obtainment. Electronic absorption spectra of the new porphyrins in CH2Cl2, EtOH and acetone, indicated a decrease in the ε (molar absorptivity) values with increasing solvent polarity, except for the nickel complex which, in acetone, showed a slight increase of 2% in the ε value. The dielectric measurements showed that the conductivity (σ) and the loss tangent (tan δ) increased with frequency, but the permittivity (ε') decreased. The results showed that the coordination of the porphyrin promoted a significant change in thermal and dielectric properties, specially for to the Ni-complex compound, which presented the best dielectric properties with interesting values of permittivity and loss tangent at 100 MHz (19.46 and 0.011 a.u., respectively). <![CDATA[Development and Characterization of Synthetic Chalcones-Loaded Eudragit RS 100 Microparticles for Oral Delivery]]> Eudragit® RS100 microspheres of two chalcones were prepared by solvent evaporation technique. A simple and rapid high-performance liquid chromatography (HPLC) method was developed and validated to determine the encapsulation efficiency, drug loading and release profiles of these chalcones in a microparticulate system. The mean EE values for the two chalcones-loaded microparticles were 98.8 ± 1.3% and 99.5 ± 0.9%. Scanning electron microscope (SEM) studies showed that one chalcone-loaded microspheres are spherical and smooth appearance whereas the other chalcone-loaded microspheres showed irregular particles and a rough surface. The analysis of the second chalcone by thermogravimetric analysis (TGA) showed a higher thermal stability compared to the first chalcone. Drug release profiles were determined at pH 7.4 phosphate buffered saline (100 mmol L-1) with sodium lauryl sulfate (0.5%). The systems prepared with Eudragit® showed 78 and 95% of the two chalcones were released after 24 hours. The experimental results indicated that the prepared polymeric microspheres may be useful for potential applications. <![CDATA[Strategy for Correction of Matrix Effect on the Determination of Pesticides in Water Bodies Using SPME-GC-FID]]> This paper investigates a strategy as a quality control parameter, using standard surrogate and determination of a relation factor for determination of parathion-methyl, chlorpyriphos and cypermethrin pesticides in environmental aqueous matrices with distinct characteristics (river water, estuarine, seawater and weir water), using the technique of solid phase microextraction gas chromatography with flame ionization detector (SPME-GC-FID). Pesticides were very susceptible to matrix effects promoted by environmental samples. The salinity and the organic matter seem to have been the main sources of interference in the method. For chlorpyriphos, in middle and high levels, the values of relation factor (Rf) for estuarines, seawater and weir matrices were statistically similar. For cypermethrin, the statistical equality occurred in estuarine matrices in medium and high levels of concentration. That indicates proportional behavior between the pesticide and the surrogate recovery, suggesting that a single value of Rf can be used as correction factor recovery for any of these matrices. <![CDATA[Electrooxidation of Mixed Ethanol and Methanol Solutions on PtSn/C Electrocatalysts Prepared by the Polymeric Precursor Method]]> Different mass ratio proportions of PtSn (m/m) electrocatalysts with 20% metal loading on a carbon support were prepared for use in ethanol:methanol solutions oxidation reactions. PtSn/C (3:1) (91% alloy degree, lattice parameter of 0.399 nm and mean crystallite size 4.8 nm) presented the best activity for oxidation of mixed solutions. The highest normalized current (ethanol:methanol 80:20) was 4.2 mA mgPt-1 (measured after 1800 seconds at 0.5 V). Therefore, the PtSn/C (3:1) electrocatalyst with an atomic ratio of 65:35 enhanced both the electronic effect and bifunctional mechanism in (ethanol:methanol 80:20), which resulted in the formation of CO2 at low potentials, as well as the highest amount of by-products than ethanol and methanol. <![CDATA[Thermodynamic Feasibility of Pure Hydrogen Production and Storage in Iron and Germanium Based Double Chemical Looping Process]]> Solid iron based low or medium temperature chemical loop is considered as a possible option of hydrogen storage and production. In the method, hydrogen is produced via iron oxidation with steam, and in the next phase iron oxide is reduced with hydrogen, synthesis gas or methane. In the reduction stage the reaction is terminated when the atmosphere still contains a large fraction of the reducing agent (often over 70 vol.%). In the paper the innovative idea of a double, iron and germanium based, chemical cycle was proposed. The thermodynamic calculations show that the reduction stage in the double iron-germanium cycle is more effective than the classical iron based loop. <![CDATA[Antitubercular Activity Increase in Labdane Diterpenes from <em>Copaifera</em> Oleoresin through Structural Modification]]> The labdane diterpenes copalic acid, 3β-acetoxy-copalic acid, 3β-hydroxy-copalic acid and ent-agathic acid were isolated from Copaifera langsdorffii oleoresin. These four compounds were submitted to structural modifications by reduction with hydrogen/palladium, esterification with diazomethane, esterification with methanol/sulfuric acid and conversion into sodium salt, furnishing 15 compounds. All compounds were assayed in vitro against Mycobacterium tuberculosis (H37Rv, ATCC 27294). The four compounds displayed minimum inhibitory concentration (MIC) value of 125 µg mL-1, and were not considered active. A methylated derivative of compound 3β-hydroxy-copalic acid, and a sodium salt of copalic acid displayed MIC values of 25 µg mL-1 (71.7 µM) and 6.25 µg mL-1 (19.2 µM), respectively. The sodium salt of copalic acid stood out by displaying similar activity in comparison with streptomycin (MIC 6.25 µg mL-1) and a better activity compared to µM value of pyrazinamide (MIC 3.12 µg mL-1; 25.34 µM). Therefore, the methylated derivative of compound 3β-hydroxy-copalic acid and the sodium salt of copalic acid should be considered for further studies. <![CDATA[Study of Viability of Solid-Phase Microextraction, <em>in vivo</em>, in the Extraction of Microbial Volatile Organic Compounds Associated to the Pigment Production Process by the <em>Monascus</em> Fungus, in Submerged Fermentation]]> Microbial volatile organic compounds (MVOCs) are present in several production processes in biotechnology. In this study it is evaluated the viability of use of a method involving solid-phase microextraction (SPME), in vivo SPME, in the extraction of MVOCs, associated with the pigment production process by the Monascus fungus. PDMS/Car/DVB (50/30 µm) fiber in the headspace mode (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used to fermentation broth study. Seventeen compounds were found associated with the presence of the fungus, being the main ones ethanol, 2-methyl-propanol, 3-methyl-butanol, 2-methyl-butanol and 2-phenyl-ethanol. These compounds have maximum concentration of 313.87, 5.51, 2.37, 0.95 and 0.70 mg L-1. The values of biomass and red pigment found for fermentation for ten days were 4.03 ± 0.21 g L-1 and 3.96 ± 0.17 (UA480). Regular MVOC productions were observed in this study, which were useful in the prediction and control of fermentation by Monascus fungus. <![CDATA[Ethylene Glycol Electro-Oxidation on Platinum-Free Surfaces: How the Composition of PdRuRh Surfaces Influences the Catalysis]]> In this work we performed electrochemical (cyclic voltammetry and chronoamperommetry) and spectroelectrochemical studies (in situ Fourier transform infrared (FTIR)) in PdRuRh electrodeposits in acidic media in presence of ethylene glycol (0.5, 1.0 and 2.0 mol L-1). The electrochemical results show that the ethylene glycol oxidation is sensitive to the composition of the catalysts, being PdRuRh 74:09:17 the composition which presents the best catalytic activity. Also, conversely to Pt, these surfaces do not present a self-inhibitory effect when the EG concentration is increased. FTIR results indicate a complex reaction mechanism under these conditions, where glycolic acid, oxalic acid, formic acid and CO2 are detected as electro-oxidation products. The best catalytic activity observed for PdRuRh 74:09:17 can be understood in terms of a higher selectivity towards the production of CO2, which is the oxidation pathway that involves the release of the major number of electrons. <![CDATA[A New Prenylisoflavone from the Antifungal Extract of Leaves of <em>Vatairea guianensis</em> Aubl.]]> A new compound, 5,7,3'-trihydroxy-4'-methoxy-8-prenylisoflavone, was isolated from the leaves of Vatairea guianensis Aubl. (Fabaceae), together with two known isoflavones lupiwighteone and 5,7,4'-trihydroxy-3'-methoxy-8-prenylisoflavone. All isolated compounds were characterized based on infrared (IR), UV, 1H and 13C nuclear magnetic resonance (NMR), including 2D NMR analyses and high resolution mass spectrometry. The ethanolic extract from V. guianensis leaves displayed activity against Candida dubliniensis, C. albicans and C. krusei. However, the EtOAc fraction from that extract exhibited more significant activity than the ethanolic extract, showing antifungal activity for all fungi species investigated. The major compound 5,7,3'-trihydroxy-4'-methoxy-8-prenylisoflavone isolated from that EtOAc fraction was also active against C. parapsilosis and C. dubliniensis. <![CDATA[Eco-Friendly, Catalyst and Solvent-Free, Synthesis of Acetanilides and <em>N</em>-Benzothiazole-2-yl-acetamides]]> An expeditious and green synthesis of acetamides in a solvent-free simple way is described, without catalyst or additives, and in good yield by an instantaneous reaction of anilines or 2-aminothiazoles and acetic anhydride without external heating, and with simple purification. Sixteen substituted acetanilides and four N-benzothiazole-2-yl-acetamides were formed, but aliphatic amines of low molecular weight were not as effective as aromatic ones, and only cyclohexylamine and the enaminone ethyl 3-amino-2-butenoate afforded the corresponding acetamides in good yield.