Resumo em Português:

Hop flowers contain chemical substances that are used to confer sensory properties to beer. Hop flower products have very high commercial value, but national production represents less than 2% of domestic consumption. In this work, flowers from different hop cultivars grown in northeast of Brazil (Rio Grande do Norte and Ceará) were analyzed to quantitate metabolites of industrial interest. Flowers from the initial and three consecutive harvests were collected, and bitter acids and xanthohumol were evaluated by HPLC-UV and essential oils by GC-MS. The cultivar Columbus was subjected to only 10% of the irrigation time during the third flowering phase to evaluate the effect of water stress on the formation of metabolites. Compounds were detected in appreciable quantities in all samples, and consecutive flowering of some cultivars showed a significant increase in total bitter acids with successive harvests. Plants subjected to water stress showed an abrupt decrease in the concentration of compounds. The cultivars evaluated by liquid and gas chromatography showed a significant concentration of bitter acids and essential oils within the expected range, and the chemical composition of the oils showed different compounds characteristic of hops.

Resumo em Português:

It is challenging to reveal the catalytic mechanism of Cu/ZnO catalysts with multivalent copper and improve the performance of CO2 hydrogenation to methanol. We synthesized Cu/ZnO catalysts with different Cu:Zn ratios using acetylacetone salts as the precursors, in which Cu, Cu2O, CuO coexist. The catalytic activity was significantly associated with the abundance of Cu+ active sites on the surface and the formation of more Cu+-ZnO interfaces. When the ratio of Cu:Zn = 5:4, the catalyst without reduction pretreatment showed good performance, with a CO2 conversion rate of 12.9%, methanol selectivity of 85.1%, and the space-time yield of 0.238 gMeOH gcat−1 h−1. It was suggested that Cu+ tends to closely bind with ZnO, and the preparation method leads to more Cu+-ZnO interfaces. The synergistic interaction between Cu+ and ZnO promoted the adsorption and dissociation of CO2 and H2, verifying its dual effect on CO2 and H2 and promoting CO2 hydrogenation to methanol.

Resumo em Inglês:

This work describes the first chemical study on the metabolic profile of three geopropolis samples from Melipona fulva, M. compressipes, and M. paraensis collected in the Amazonian region. The samples were submitted to solvent extractions. The silylated hexane extracts were submitted to GC-MS analysis and tentatively identified mainly the presence of triterpenes, steroids, fatty acids, and alcohols. The chemical profile of M. fulva of and M. compressipes geopropolis are similar. However, cholesterol, triacontanol, and palmitic acid are the main compounds in M. fulva; in M. compressipes, palmitic acid, linoleic acid, and oleic acid are predominant. The chemical profile of the M. paraensis sample is entirely different once more than 60% of the extract comprises lupenone and triacontanol. The CHCl3 soluble fraction of the MeOH extract of the M. paraensis geopropolis was submitted to chromatographic techniques, and it afforded cycloartenol, 24-methylene-cycloartenol, lupeol, α- and β-amirins, and 7-O-methylaromadendrin. The MeOH extract of this sample presents antimicrobial activities against strains of Streptococcus mutans, S. sobrinus, and S. aureus (MIC of 15.6-62.5 µg mL−1 and MBC of 62.5-1000 µg mL−1). The M. fulva and M. compressipes geopropolis were not active in this test.

Resumo em Inglês:

Schinopsis brasiliensis Engl. (braúna) is a tree species of the Anacardiaceae family. It is native to Brazil, Paraguay, and Bolivia. It is a candidate for agro-industrial system that can be used to produce phytotherapeutics and bioproducts. However, to comprehensively understand the characteristics of plant within the framework of sustainable development for agro-industries, exploring the chemical and phenotypic diversity of samples from various microenvironments across different collection periods is essential. Accordingly, herein, the influence of different environmental factors and sample collection durations on braúna samples was investigated over several years using multivariate statistical analyses associated with nuclear magnetic resonance (NMR) spectroscopy. Bark samples from different areas and environmental data from different locations were analyzed. Distinct chemical profiles were observed across reserve, forest, and management areas, all marked by elevated sugar levels suggesting water stress adaptation. High radiation and low rainfall correlated with increased sugar and amino acids. Each microenvironment responded uniquely to these environmental conditions. Consequently, plant samples from different microenvironments collected over different periods were observed to respond differently to environmental factors, such as solar radiation and temperature. We correlated the metabolomic data with climatic data evaluating the influence of abiotic factors on the production of metabolites in braúna bark samples.

Resumo em Inglês:

Cellulose nanocrystals (CNCs) were grafted with poly(N-isopropylacrylamide) (PNIPAM) chains, by means of the grafting from route, using the TEMED/KPS redox pair as free-radical initiators. The confirmation of grafting was revealed by 13C NMR spectra. In a test with murine macrophages (RAW 264.7 cell line), CNC-g-PNIPAM copolymers did not affect cell viability nor RAW cell oxide nitric production. Raw cells exposed to oxidative stress induced by H2O2 decreased the cell viability (~ 60%) and increased lipid peroxidation, as revealed by malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD) levels. The most effective protection against the oxidative damage, with cell viability of 100%, was provided by 50 µg mL−1 of CNC-g-PNIPAM synthesized with 1:1 CNC:NIPAM mass ratio. Furthermore, there was no significant difference between the levels of GSH, MDA and SOD between cells treated with the modified CNC and cells not exposed to peroxide. These results indicate that the antioxidant properties of CNC-g-PNIPAM may be useful in possible applications in health treatments.

Resumo em Inglês:

In recent years, various methods for surface functionalization of magnetite nanoparticles with emerging modifications have been explored and reported. Green nano-chemistry aims to synthesize nanomaterials using bio-based resources, providing new materials for biological and environmental applications. Surface modification of magnetite nanoparticles using phytochemicals extracted from plants is a fundamental principle of green synthesis routes. Agricultural waste from different crops, such as plantain pseudostem, is of particular interest as a renewable resource due to its abundant availability, low toxicity, and economic feasibility. In this study, the juice extracted from plantain pseudostem was utilized for the phytofunctionalization of magnetite nanoparticles. Characterization techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and fourier-transform infrared spectroscopy (FTIR) confirmed the nanometric dimensions of the composite (size range of 12.6 ± 3.17 nm) and established its organic-inorganic nature. The superparamagnetic properties of the composite were also demonstrated. Moreover, the potential application of this nanohybrid in bioremediation for the immobilization of cadmium(II) and lead(II) showed promising results, highlighting its efficacy in managing water pollutants.

Resumo em Português:

The process of photosynthesis involves the absorption of light energy by photosynthetic pigments found in the thylakoid membrane of chloroplasts in order to produce chemical energy. In the presence of photosynthetic inhibitors, plant development is affected mainly by the reduction of the electron chain, which leads to growth inhibition. In this context, chlorophyll a (Chl a) fluorescence is an important technique used to identify the effects of inhibitors on the photosynthetic apparatus employing the JIP-test, which correlates the Chl a fluorescence transient to biophysical parameters, providing valuable information about the efficiency of photosystems I and II. Natural products have been highlighted as photosynthesis inhibitors due to the continued use of synthetic herbicides, which leads to the development of invasive plants resistant to these pesticides, in addition to the toxicity caused to humans and the environment. Thus, this review describes the main applications of extracts and isolated secondary metabolites obtained from plants and microorganisms in the investigation of electron transport inhibition on photosystem II.

Resumo em Inglês:

The present review, with 169 references, describes a critical updated compilation of studies regarding the Anacardiaceae family. Firstly, it is shown a detailed report of the chemical composition (essential oils, terpenoids, flavonoids, alkyl and alkenyl phenols, and other compounds) of species of all studied genera, followed by the biological properties (in vitro and in vivo activities) of extracts, enriched fractions, and pure new isolated metabolites. Furthermore, it is reported herein that some deposited processes developed with Anacardiaceae spp. (cosmetic and pharmacological compositions, besides some technological applications) as well as new findings about the biosynthesis of phenolic lipids, the primary chemical marker of the family. Consequently, these outcomes highlight the relevance of this family in developing natural products’ chemistry from 2006 to now.

Resumo em Português:

The present review presents the biotechnological potential of microalgae, highlighting its applications in biofuels, bioremediation, production of bioactive compounds, biocatalysts, and biofertilizers. Microalgae are photosynthetic microorganisms that combine characteristics of plants and heterotrophic microorganisms, such as yeasts, bacteria, and fungi. They can be considered biotechnological agents of extreme versatility and metabolic adaptability. Its photosynthetic efficiency can absorb large volumes of anthropogenic CO2 and convert it into biomass rich in compounds of high biological and energetic value, enabling the development of sustainable bioremediation processes and the production of third-generation biofuels and biofertilizers. In addition, its biomass has aroused interest in obtaining compounds with biological action, such as carotenoids, mycosporine-like amino acids, polyunsaturated fatty acids, sterols, phycocolloids, carbohydrates, and proteins. The biotechnological potential of microalgae does not end with the production and extraction of its biomass. Its dynamic and adaptive metabolism allows its use in the biotransformation of xenobiotic substrates and the production of compounds of chemical and pharmaceutical interest. In this perspective, microalgae have application qualities as a biotechnological platform in developing synergistic processes between the environment, society, and industry, thus contributing to the expansion and use of Green Chemistry and strengthening the circular economy.

Resumo em Português:

Fluorescence spectroscopy is an extremely sensitive analytical technique that has been widely used to elucidate problems that require low detection limits. Although fluorescence spectroscopy is widespread in industry and academia, there is a lack of teaching materials demonstrating its basic principles, as well as the influence of instrumental parameters involved in the technique, which limit its correct use and the full potential of it. For this reason, this work aims to explore the principles of fluorescence spectroscopy and correlate them in function of different instrumental variables to carry out a fluorescence experiment. The spectrofluorometer parameters such as the excitation wavelength, excitation and emission slits, step, integration time, detection geometry as well as concentration of the samples were varied to illustrate how the best resulting spectra can be registered free of artifacts. To do so, two organic dyes with structured vibronic bands (pyrene) and another with unstructured bands (rhodamine 6G) were used. Another study carried out involved the use of 3D spectra, excitation/emission spectra, of cadmium telluride (CdTe) quantum dots. In this case, it was possible to show the excitation spectrum of nanomaterials, collecting emissions at different wavelengths, as well as analyzing the particle size distribution.

Resumo em Português:

As catalysis grows as a multidisciplinary research area, many questions arise regarding the procedures used to determine the activity of materials in different chemical reactions. To correct inconsistencies, whether in definitions, concepts, or experimental methods, some catalysis science journals have been publishing editorials warning less-aware authors. In this work, we present some common concepts and procedures in thermo-catalysis, reviewing good practices and pointing out frequent failures that make it difficult to reliably compare the activity between materials of the same family and results from the scientific literature.

Resumo em Português:

Electronegativity is a useful chemical bonding property related to determining the polarity of molecules and formation of partial charges. In the 1930s, Linus Pauling studied the differences between theoretical and experimental binding energy values when he established that ionic contributions in covalent bonds were pertinent to elucidate these differences. The association of the nature of the elements present in the chemical bond with the discordance of results led to the quantitative determination of electronegativity, creating the first scale of this property. In addition, other scales were developed, such as by Robert Mulliken (1934), Albert Allred and Eugene Rochow (1958) and Leland Allen (1989). Although present in undergraduate Chemistry courses, the teaching of electronegativity is little explored in the literature and treated in a fragmented way in many materials. In this way, a didactic sequence is proposed for the approach of electronegativity and the scales designed by Pauling, Mulliken, Allred, Rochow and Allen directed to the first year of undergraduate in Chemistry. For a dynamic study of electronegativity models along with historical basement, modelling-based teaching is used so that students can assess scope, limitations and be able to participate in the creation of a model.