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Química Nova, Volume: 47, Issue: 7, Published: 2024
  • MULTI-ELEMENT DETERMINATION IN BIODIESEL SAMPLES USING ENERGY DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY AFTER EXTRACTION INDUCED BY EMULSION BREAKING Artigo

    Almeida, Jorge S.; Domingos, Stênio G.; Meira, Lucilia A.; Teixeira, Josanaide S. R.; Teixeira, Leonardo S. G.

    Abstract in Portuguese:

    A method for determining Cd, Cr, Cu, and Fe in biodiesel samples is proposed using energy dispersive X-ray fluorescence spectrometry (EDXRF) after extraction induced by emulsion breaking (EIEB). A volume of 7.0 mL of biodiesel and an aliquot of 500 µL of Triton X-100 solution (2%, v v-1) prepared in nitric acid were used to prepare the emulsion. After 5 min of manual agitation, phase separation was performed by centrifugation for 5 min at 2000 rpm. A 100 µL aliquot of the enriched aqueous phase was collected and applied to the center of a filter paper. After drying, the analysis was performed directly on the paper using EDXRF. The detection limits were 60, 20, 30, and 60 μg kg-1 for Cd, Cr, Cu, and Fe, respectively. Recovery tests were performed by adding 450 μg kg-1 of the analytes in biodiesel samples, and the results varied between 87 and 113%. The procedure was applied to biodiesel samples, and the concentrations obtained for the four analytes were compared with those obtained by inductively coupled plasma optical emission spectrometry (ICP OES) after sample digestion.
  • OCCURRENCE OF DIETHYL PHTHALATE (DEP) IN FOOD USING DIFFERENT PACKAGING: DETECTION AND TRACEABILITY Article

    Almeida, Maria Carolina de; Sá, Fernando Pereira de; Ishizawa, Taís Aragão; Silva, Flávio Alves da; Pereira, Julião; Oliveira, Tatianne Ferreira de

    Abstract in English:

    The objective of this work was the detection and traceability of the occurrence of diethyl phthalate (DEP) migrating from flexible packaging to food. Brazil is one of the largest producers of flexible plastics widely used in food. The evaluation of migrations of contaminants for food, mainly fatty foods, elucidates the possible transmission of diseases through the daily consumption of migrant contaminants from packaging. Throughout an accurate and highly specific methodology, with no use of simulants or organic solvents during sample preparation, the proposal of this study obtained a direct DEP ranking through migration traceability via headspace: HS-GC-MS. Of the 9 samples of flexible packaging and packaged foods analyzed, DEP was identified in 100%, thus confirming its occurrence in foods. Despite the storage conditions: temperature, shelf life, fat content of the products and the manufacturer’s assessment of use. It is urgent to review official standards to promote intense restrictions on the occurrence of DEP in food and encourage the benefits of reflecting daily consumption habits.
  • BISMUTH OXYCHLORIDE NANOSHEETS MODIFIED WITH AU-CU NANOPARTICLES FOR EFFICIENT PHOTOREDUCTION OF CO2 TO ETHANE Article

    Zou, Xia; Wang, Sisi; Zheng, Xingxing; Yang, Jun

    Abstract in English:

    BiOCl nanosheets modified with AuCu nanoparticles were successfully designed and fabricated for water reduction of CO2. The AuxCuy/BiOCl composites exhibited enhanced visible light absorption ability due to a surface plasmon resonance (SPR) effect. The AuxCuy/BiOCl composites could convert carbon dioxide to ethane (C2H6), while only CO was obtained over pure BiOCl nanosheets. In this study, the rate of C2H6 production (12.2 μmol h-1 g-1) and selectivity of C2H6 (75.7%) were obtained over the Au1Cu1/BiOCl photocatalyst under simulated sunlight illumination. The AuCu nanoparticles played the dual role of electron traps and hot electron donors, facilitating efficient separation and migration of the carriers. The photocatalyst exhibited steady photocatalytic activity over the test duration of 9 h.
  • SYNTHESIS OF CHIRAL 1,5-DIAMINES DERIVED FROM (R)-(+)-CAMPHOR Article

    Martins, José E. D.; Kray, Luciana J.; Santos, Greice M. dos

    Abstract in English:

    In this work we described the synthesis and characterization of a series of novel chiral 1,5-diamines derived from (R)-(+)-camphor through simple procedures in moderate to good yields. These new enantiopure compounds constitute a new family of chiral diamines with potential applicability as chiral building blocks, bioactive products or chiral ligands for asymmetric transformations.
  • USE OF BREWERY SPENT GRAINS FOR THE PREPARATION OF BIOPLASTICS: A PROPOSAL FOR A CIRCULAR ECONOMY TO THE BREWING SECTOR Artigo

    Arantes, Giovanna Cassiano Azevedo; Silva, Sandy Chaves da; Dutra, Romulo Coriolano; Drummond, Adriana Linhares; Ghesti, Grace Ferreira

    Abstract in Portuguese:

    There is a demand for new technologies to replace fossil resources in activities due to environment concerns. In the circular economy, materials to be discarded are reused and reenter to the economy. An alternative for the plastic problem would be preparation of fiber-reinforced plastics from renewable sources. Herein polymeric films were prepared with starch, glycerol and bagasse derivatives. Some characterization techniques were presented to indicate the best applications. It was identified that higher glycerol ratio films are more malleable and have a higher humidity and solubility. The DSC scans for each film shows no increase in glass transition temperature. Biodiesel films are an alternative for the circular economy of waste and the biodiesel industry, since the study proved to be an alternative for the plastics currently used. This work will certainly attract the students’ interest, because the theme is in their daily lives, also bringing the precepts of sustainability and green chemistry.
  • LIPASE FROM RHIZOPUS ORYZAE IMMOBILIZED ON CORN COB POWDER: A NEW APPROACH FOR DIETETIC TRIGLYCERIDE SYNTHESIS IN A FIXED BED REACTOR Article

    Pacheco, Bruna Jeanne Soares; Andrade, Grazielle Santos Silva; Paula, Ariela Veloso de

    Abstract in English:

    This work explores the possibility of using corn cob powder as a carrier for immobilization by physical adsorption of lipase from Rhizopus oryzae used in acidolysis reaction of grape seed oil with capric acid (C10) to synthesize dietary triglycerides (TAGs) formed from medium-long-medium chain (MLM) fatty acids in a fixed bed reactor. First, enzymatic loading was investigated to improve hydrolytic activity and the immobilized biocatalyst was characterized in terms of biochemical parameters and thermal stability. An enzyme load of 30 mg mL-1 was quite adequate, as about 90% of the immobilization yield was achieved. The central composite rotatable design (CCRD) experimental design revealed that, for the immobilized enzyme, the optimal hydrolytic activity was obtained at pH 7.75 and 41 °C. Stirred tank reactions were optimized in CCRD statistical analysis revealing the most desirable conditions for molar ratio of 1:9.36 (oil:acid), 45 °C and 15% biocatalyst, obtaining a maximum ID value of 86.93 ± 2.25%. In a fixed bed reactor, the synthesis showed an average ID of 51.13 ± 0.77, demonstrating the potential of this configuration. It is concluded that corn cob powder as an immobilization carrier is a promising alternative for the enzymatic synthesis of MLM triacylglycerols.
  • SYNTHESIS, BIOCHEMICAL AND IN SILICO EXPLORATION OF NOVEL IMIDAZOLE BASED 1,2,3-TRIAZOLES AS POTENTIAL HIT AGAINST CARBONIC ANHYDRASE II ISOZYME Article

    Hussain, Mumtaz; Channar, Pervaiz Ali; Alsfouk, Aisha A.; Ejaz, Syeda Abida; Aziz, Mubashir; Hussain, Zahid; Kandhro, Ghulam Abbas; Attaullah, Hafiz Muhammad; Ujhan, Rabail; Jakhrani, Mushtaque Ali; Saeed, Aamer; Abbas, Qamar; Abualigah, Laith

    Abstract in Portuguese:

    This study aimed to synthesize novel compounds as more effective carbonic anhydrase II inhibitors. For this purpose, 2-(3-methoxy-4-(prop-2-yn-1-yloxy)phenyl)-4,5-diphenyl-1H-imidazole (3) was reacted with 3-methoxy-4-(prop-2-yn-1-yloxy)benzaldehyde through the glyoxal reaction to produce a series of imidazole-based 1,2,3-triazoles 5a-f. The synthesized compounds were structurally confirmed using IR, 1H, and 13C NMR techniques. To evaluate their potential as inhibitors of carbonic anhydrase II enzyme, the synthesized compounds were tested via in vitro enzyme inhibition assay. Among the derivatives, compounds 5f and 5a exhibited the most promising inhibitory potential, with IC50 values of 0.025 ± 0.001 and 0.032 ± 0.003 µM, respectively. Both 5a and 5f derivatives have comparable inhibitory potential but 5f was found to be more potent than 5a: Molecular docking analysis revealed that compounds 5a and 5f displayed excellent binding scores of -8.0 and -8.4 kcal mol-1, respectively. The results were further validated by MD simulations. The RMSD analysis revealed the average values of 3.20 Å for the ligand-protein complex, 1.38 Å for the apoprotein, and 7.15 Å for the ligand molecule. Based on the chemical stability and biological importance, the compound 5f was identified as potential lead candidates for the development of more effective carbonic anhydrase II inhibitors.
  • DETERMINATION AND DISTRIBUTION OF Cu, Fe, AND Zn IN CAMAPU BY ICP-OES Artigo

    Pereira, Cecilia Correia; Lemos, Michelle de Souza; Dantas, Kelly das Graças Fernandes

    Abstract in Portuguese:

    This study aimed to determine the total contents of copper, iron, and zinc in camapu and protein fractions by inductively coupled plasma emission spectrometry. Firstly, lipid removal was performed using chloroform and methanol (2:1). Protein fractions were obtained after sequential extraction using four extractors (water, 0.5 mol L-1 sodium chloride, 50% acetic acid v v-1 and 0.05 mol L-1 sodium hydroxide). The camapu sample and protein fractions were digested in a cavity-microwave oven with diluted nitric acid and hydrogen peroxide. The accuracy of the procedure was evaluated using the addition and recovery method in the digests and protein extracts. All the elements were determined in the protein fractions. Levels of Cu, Fe, and Zn ranged from 0.07 to 0.5 mg kg-1 were found in the lipid fraction. The residue presented higher iron content compared to other elements. Higher Cu and Zn contents were found associated with albumin. All elements studied were found in the protein fractions, and the total protein concentration determined in each protein fraction was 5.74 mg kg-1 (albumins), 0.28 mg kg-1 (globulins), 4.46 mg kg-1 (glutelins 1) and 0.46 mg kg-1 (glutelins 2).
  • USE OF CHITOSAN FILMS TO REMOVE BORDEAUX S FOOD COLORING WITH QUANTIFICATION BY DIGITAL IMAGE ANALYSIS Artigo

    Sá, Igor Coreixas de; Feiteira, Fernanda Neves; Dornellas, Rafael Machado; Pacheco, Wagner Felippe

    Abstract in Portuguese:

    Bordeaux S is a food dye still allowed in Brazil, being present in soft drinks, gelatins, chewing gums, candies and many other industrialized foodstuffs. Because of its carcinogenic potential, it is forbidden to be added to food in Japan, in the USA and in most of the European Union. Many studies related to the employment of digital images analysis to food quality control have been published in recent years mainly due to its low costs of implementation. Nevertheless, one of the few drawbacks of applying this technique is its poor sensitivity, which can be significantly improved by employing solid substrates, such as chitosan films. In this work, chitosan sorbent films were synthesized, characterized and used to retain Bordeaux S present in gelatin samples, followed by recording the films’ images and quantifying the analyte by digital images analysis. The proposed method was able to extract the analyte and eliminate interferences present in the matrixes in a single step. LOD of 20 µg L-1 and LOQ of 74 µg L-1 were obtained, allowing adequate quantification when considering the recommendations of the Brazilian Health Regulatory Agency (ANVISA).
  • FLAVONOIDS AND PHENOLIC ACIDS ISOLATED FROM Macrolobium acaciifolium (FABACEAE) LEAVES AND BRANCHES METHANOLIC EXTRACTS Artigo

    Silva, David R.; Nunez, Cecilia V.

    Abstract in English:

    FLAVONOIDS AND PHENOLIC ACIDS ISOLATED FROM Macrolobium acaciifolium (FABACEAE) LEAVES AND BRANCHES METHANOLIC EXTRACTS. The phytochemical study of Macrolobium acaciifolium extracts allowed the isolation and identification of 18 substances, 15 of which are reported for the first time in this species. From the methanolic extract of the leaves, the flavonoids luteolin-3’-O-α-L-rhamnoside (1), neoastilbin (2), astilbin (3), neoisoastilbin (4), isoastilbin (5), quercetin-3-O-α-L-rhamnoside (6), quercetin-3-O-rutinoside (7), kaempferol-3-O-rutinoside (8), quercetin-3-O-glicoside (9) and kaempferol-7-O-rutinoside (10) were isolated. From the methanolic extract of branches, the flavonoids chrysoeriol (13), apigenin (14), 7,4’-dihydroxyflavone (16), eriodictyol (17) and luteolin (18), in addition to the phenolic acids 3,4-dihydroxybenzoic acid (11), 3-methoxy,4-hydroxybenzoate (12) and methyl 3,4-dihydroxybenzoate (15) were isolated. The structural identification of the compounds was established by proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC) and correlated spectroscopy (COSY) analyses. In this paper, we also discuss about the anisotropic effects on H-1”, H-2”, H-5” and H-6” rhamnose of isomers dihydroflavonoids.
  • DETERMINATION OF MAILLARD REACTION MARKERS IN DOCE DE LEITE BY HPLC-PDA Article

    Pinto, Caroline Barroso dos Anjos; Cunha, Carolina Neves; Mesa, Natalia Casas; Sad, Maria Esther Leal da Silva; Stephani, Rodrigo; Perrone, Ítalo Tuler; Costa, Juliana de Carvalho da

    Abstract in English:

    This study was carried out as a preliminary mapping of Maillard reaction (MR) compounds in doce de leite (DL), as possible indicators for the intermediate stage and chemical pathways in industrial processing. For that, the objective of the manuscript was to developed and validated an analytical method to simultaneously analyze four furfural compounds in DL: 5-hydroxymethylfurfural, 2-furaldehyde (F), 2-furyl-methyl ketone (FMC) and 5-methyl-2-furaldehyde (MF) by high performance liquid chromatography-photodiode-array detector (HPLC-PDA). The method fulfilled the acceptance criteria: selectivity, linearity (0.16-5 μg mL-1 for HMF, and 0.06-2 μg mL-1 for F, FMC and MF, R2 > 0.9974), precision (CV = 1.33 to 2.12% for HMF; 1.57 to 4.34% for F; 0.84 to 1.40% for FMC and 1.40 to 4.18% for MF), accuracy (94.40 to 102.25% for HMF; 92.91 to 108.15% for F; 90.13 to 108.48% for FMC and 93.31 to 107.70% for MF), limit of detection of 0.041 μg mL-1 for HMF; 0.030 μg mL-1 for F; 0.042 μg mL-1 for FMC and MF, and limit of quantification of 0.125 μg mL-1 for HMF and F, 0.066 μg mL-1 for FMC and 0.1280 μg mL-1 for MF. Thus, it was concluded that an analytical method was developed and validated for quantifying HMF, F, FMC and MF in DL.
  • THEORETICAL STUDY OF MOLECULES DERIVED FROM BETA-LACTAMS COMPOUNDS WITH POSSIBLE POTENTIAL ANTIBIOTIC ACTIVITY ON Staphylococcus aureus Article

    Anaya-Gil, Jorge; Mercado-Beltrán, Gina; Guerrero-González, Ana; Mercado-Camargo, Jairo; Ahumedo-Monterrosa, Maicol; Vivas-Reyes, Ricardo

    Abstract in English:

    Staphylococcus aureus is known worldwide as the principal cause of human bacterial infections; as well as methicillin-resistant Staphylococcus aureus (MRSA), is a major cause of hospital-acquired infections that are becoming increasingly difficult to combat because of emerging resistance to all current antibiotic classes. This work aims to carry out a theoretical study of molecules derived from beta-lactam compounds with possible potential antibiotic activity on Staphylococcus aureus. Therefore, computational chemistry tools were used to describe the interactions between potentially active molecules and the transpeptidase and beta-lactamase enzyme. These molecules were docked with transpeptidase and beta-lactamase enzymes, and all of them showed a higher affinity for transpeptidase (−1.81 kcal mol−1) than the reference molecule (methicillin), but only two showed a lower affinity for beta-lactamase (−6.8 kcal mol−1). The two ligands that presented the best ranking docking results were subjected to molecular dynamics simulations to assess conformational stability through root mean square deviation (RMSD) and root mean square fluctuation (RMSF) analysis. According to simulation, the ligands that bind to the proteins do not cause significant conformational changes in the structures of the proteins. The absorption, distribution, metabolism, and excretion (ADME) properties of the molecules with the lowest affinity for beta-lactamase were estimated. The ADME properties predict that the molecules would have good bioavailability.
  • SYNTHESIS OF PRIMARY AMINES FROM THE REDUCTION OF AROMATIC NITRO COMPOUNDS THROUGH SUSTAINABLE REACTION PROTOCOLS PART II: REACTIONS IN ORGANIC MEDIA Revisão

    Pinto, Ligia S. da S.; Facchinetti, Victor; Bernardes, Breno de S.; Costa, Thamires M. da; Silva, Letícia de O. J. L. da; Macedo, Daniel M.; Oliveira, Isabela P. de; Vasconcelos, Thatyana R. A.; Souza, Marcus Vinícius N. de

    Abstract in Portuguese:

    The reduction of nitroarenes is the main methodology to produce anilines, important precursors of building blocks, dyes, and drugs. Continuing our goal of describing sustainable methodologies for the reduction of nitroarenes to their respective anilines, herein we compile selected reaction protocols, using organic medium, reported from 2017 to 2023, in order to provide a comprehensive and complementary view of the new processes and catalysts developed during this period.
  • PHARMACEUTICALS IN THE COVID-19 PANDEMIC: A THEME TO CRITICAL ENVIRONMENTAL EDUCATION ON ANALYTICAL CHEMISTRY TEACHING Educação

    Cecilio, Mariana S.; Passos, Camila G.; Pazinato, Maurícius S.; Sirtori, Carla

    Abstract in Portuguese:

    During the COVID-19 pandemic, the pursuit of a cure for the disease resulted in an excessive consumption of various pharmaceuticals, even after their inefficacy had been scientifically demonstrated. This scenario highlights the urgency of educational initiatives that improve students’ critical thinking and promote awareness of indiscriminate use of pharmaceuticals and its environmental and social implications. This research described the educational initiative “Pharmaceuticals in the COVID-19 pandemic” based on the study case method, implemented at an analytical chemistry class, and analyzed its potential on promoting Critical Environmental Education through a content analysis guided by the indicators proposed by Luz and Tonso. Students were divided into groups and studied different cases about pharmaceuticals featured in the media during the pandemic. They were expected to gather relevant data regarding the case scenario; to take a position on a socio-environmental dilemma; propose an analytical chromatographic methodology for the pharmaceutical in the case and present their results in a final report. The educational initiative was considered aligned with Critical Environmental Education principals due to the presence of six out of the seven indicators. As a future perspective, we aim to optimize the educational initiative in order to include all the indicators and students’ suggestions.
  • MACHINE LEARNING APLLIED TO QSAR Assuntos Gerais

    Menezes, Renata P. B. de; Scotti, Luciana; Scotti, Marcus T.

    Abstract in Portuguese:

    Over the years the study of the quantitative structure-activity relationship (QSAR) has transformed from a simple regression analysis to the implementation of machine learning (ML) with multiple statistics. Today ML-based QSAR models are quite important and play a notable role in drug design and screening, property prediction, biological activity, etc. ML methods applied to QSAR build classification or regression models to describe/predict the complex relationships between the chemical structure of molecules and biological activity. Even with the increase in scientific publications addressing this topic written in Portuguese, there is still a shortage of scientific articles explaining ML techniques applied to QSAR, how to build models, the types of models, algorithms, for the Brazilian scientific community. And to fill this need, we intend to approach the subject in a simple and didactic way for students and researchers who are starting in this very promising and important area. We will describe the fully explained theory of machine learning by applying QSAR, abstracting the complexity, and well-illustrated.
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