Victor Marcos Rumjanek

Estoque e qualidade da matéria orgânica de um solo cultivado com cana-de-açúcar por longo tempo

The aim of this study was to evaluate the stocks, and quality of the soil organic matter (SOM) through the use of solid state 13C nuclear magnetic resonance (13C NMR), electronic paramagnetic resonance (EPR) and fluorescence spectroscopy of a fine clay fluventic Eutrichrept after long-term sugarcane cultivation. In one area, sugarcane has been grown for 55 years no field burning before harvest. In another area managed under the traditional system the crop field has been burned before harvest for 35 years; vinasse has been applied on one part (at a rate of 120 m3 ha-1 yr -1), but not on another. The increases of 157 and 57 % in C stocks of humic acids in the area cultivated without field burning for 55 years were related with the increase in the aromaticity degree as well as lower acidity of the SOM, as shown by 13C NMR spectroscopy. The semiquinone-type free radical concentration, as observed by EPR, and intensity of fluorescence emission were higher in the humic acid extracted from soils under management system without field burning before harvest. Significant changes in the humification process were observed in the areas with crop trash preservation. However, in areas where sugar-cane fields were burnt at harvest, vinasse application for 35 years resulted in only minor changes in the organic matter quality and C stocks. These data indicate a rapid evolution of the soluble organic matter added to the soil through vinasse application.

Characterization of amide bond conformers for a novel heterocyclic template of N-acylhydrazone derivatives.

Herein we describe NMR experiments and structural modifications of 4-methyl-2-phenylpyrimidine-N-acylhydrazone compounds (aryl-NAH) in order to discover if duplication of some signals in their 1H- and 13C-NMR spectra was related to a mixture of imine double bond stereoisomers (E/Z) or CO-NH bond conformers (syn and anti-periplanar). NMR data from NOEdiff, 2D-NOESY and 1H-NMR spectra at different temperatures, and also the synthesis of isopropylidene hydrazone revealed the nature of duplicated signals of a 4-methyl-2-phenylpyrimidine-N-acylhydrazone derivative as a mixture of two conformers in solution. Further we investigated the stereoelectronic influence of substituents at the ortho position on the pyrimidine ring with respect to the carbonyl group, as well as the electronic effects of pyrimidine by changing it to phenyl. The conformer equilibrium was attributed to the decoplanarization of the aromatic ring and carbonyl group (generated by an ortho-alkyl group) and/or the electron withdrawing character of the pyrimidine ring. Both effects increased the rotational barrier of the C-N amide bond, as verified by the ΔG≠ values calculated from dynamic NMR. As far as we know, it is the first description of aryl-NAH compounds presenting two CO-NH bond- related conformations.

Organic matter quality in a soil cultivated with perennial herbaceous legumes

Using herbaceous legumes in agricultural systems yields great quantities of plant residues, allowing changes in soil organic matter quality and content over the years. This study was conducted on an Ultisol, at Seropedica, RJ, Brazil, to evaluate the effects of different perennial herbaceous legumes on soil organic matter quality. A factorial scheme with three replications was used to evaluate the species: forage groundnut cv. BR-14951 (Arachis pintoi), tropical kudzu (Pueraria phaseoloides), and siratro (Macroptilium atropurpureum). After the first cut, each plot was divided into two subplots; plants were cut and left on the soil surface or cut and removed. Soil samples of a closed area covered by spontaneous vegetation (mainly C3 plants) or by Panicum maximum were also analysed. Samples were collected from two layers (0-5 and 5-10 cm), processed for the fractionation of organic matter and the evaluation of structural characteristics of humic acids (HA). Evaluated legumes did not change total organic carbon contents, but promoted HA accumulation in the superficial soil layer. Humic acids may be used as indicators of the management effects on soil organic fractions, because there was significant incorporation of carbon and nitrogen derived from the legume residues, even for the short experimentation time (28 months). Residue management did not modify quantitative aspects of the distribution of the humified organic matter, but promoted, however, a higher condensation degree of humic acids evaluated by the elementary composition, IR and fluorescence spectroscopy.

Análise de fósforo em solo com leguminosas herbáceas perenes por meio de ressonância magnética nuclear

Abstract – The availability and the reserves of organic phosphorus are controlled by its mineralization rate andare also influenced by changes in soil management. The objective of this study was to evaluate the influence ofsoil covering with different leguminous plant on soil organic P by 31 P-NMR spectroscopy. Alkaline soil extractswere obtained from two depths (0–5 and 5–10 cm) of an Ultisol cultivated with herbaceous perennial leguminousplants ( Arachis pintoi , Pueraria phaseoloides , Macroptilium atropurpureum ). In an adjacent area, samples ofthe same soil cover with a secondary tropical forest and grass ( Panicum maximum ) were also collected. Theleguminous management was divided into with removal and without removal of shoot parts after cut on soilsurface. Phosphate monoesters are the dominant P species in all soil samples and P diesters accumulated on thesuperficial layer of secondary forest soil. The P amount of this fraction is higher for the legume covered soil whencompared with the grass covered soil. The permanence of leguminous plants on the topsoil after the cut promotedan increase in P diester/P monoester ratios. These findings can be accounted for an enhancement of P availabilityto plants in soils cultivated with leguminous plants.Index terms: cultivation, deforestation, cover crops.

Avaliação de características de ácidos húmicos de resíduos de origem urbana: I. métodos espectroscópicos (UV-Vis, IV, RMN 13C-CP/MAS) e microscopia eletrônica de varredura

Physico-chemical characteristics of humic acids obtained from urban waste (AH-CRSU) and sewage (AH-LETE) produced in the city of Rio de Janeiro, were determined through elemental analysis, total acidity, spectroscopic methods and electron scanning microscopy. The analysis of structural traits revealed some differences between the humic acids investigated. The presence of aromatic moieties was confirmed with UV-Vis spectroscopy, with more substituted systems present in the AH-LETE. IR spectroscopy showed aliphatic groups in the AH and as more complex signals due the presence of polysaccharides in AH-CRSU. Furthermore, the presence of COOH, COO-, CO2NH2, OH, was observed apart from aromatic systems. The CP/MAS 13C NMR analysis allowed to observed a higher amount of aromatic and COOH groups. showed the presence of polysaccharides, aminoacid N and OCH3 groups. The results allow to define the humic acids from urban source as of the type or like those of pedogenic origin.

Diterpenes from pinus taeda

Abstract Solvent partition and chromatographic fractionation of the wood of Pinus taeda afforded a mixture of aliphatic ketones and esters, sitosterol, stilbene and five diterpenes namely, pimaric acid, isopimaric acid, dehydroabietic acid, 12 α ,13 β -dihydroxyabiet-8(14)-en-18-oic acid and 7 α ,9 α ,11 α -trihydroxyabiet-8(14)-en-18-oic acid. The structures of these compounds were elucidated by IR, 1D and 2D NMR techniques including NOE and also mass spectral data.

Structural insights into cholinesterases inhibition by harmane β-carbolinium derivatives: a kinetics-molecular modeling approach.

The natural indole alkaloids, the β-carbolines, are often associated with cholinesterase inhibition, especially their quaternary salts, which frequently have higher activity than the free bases. Due to lack of information explaining this fact in the literature, the cholinesterase inhibition by the natural product harmane and its two β-carbolinium synthetic derivative salts (N-methyl and N-ethyl) was explored, together with a combination of kinetics and a molecular modeling approach. The results, mainly for the β-carbolinium salts, demonstrated a noncompetitive inhibition profile, ruling out previous findings which associated cholinesterase inhibition by β-carbolinium salts to a possible mimicking of the choline moiety of the natural substrate, acetylcholine. Molecular modeling studies corroborate this kind of inhibition through analyses of inhibitor/enzyme and inhibitor/substrate/enzyme complexes of both enzymes.

Soybean biodiesel methyl esters, free glycerin and acid number quantification by 1H nuclear magnetic resonance spectroscopy.

Production of alternative fuels, such as biodiesel, from transesterification of vegetable oil driven by heterogeneous catalysts is a promising alternative to fossil diesel. However, achieving a successful substitution for a new renewable fuel depends on several quality parameters. 1H NMR spectroscopy was used to determine the amount of methyl esters, free glycerin and acid number in the transesterification of soybean oil with methanol in the presence of hydrotalcite‐type catalyst to produce biodiesel. Reaction parameters, such as temperature and time, were used to evaluate soybean oil methyl esters rate conversion. Temperatures of 100 to 180 °C and times of 20 to 240 min were tested on a 1 : 12 molar ratio soybean oil/methanol reaction. At 180 °C/240 min conditions, a rate of 94.5 wt% of methyl esters was obtained, where free glycerin and free fatty acids were not detected. Copyright

Diastereoselective Synthesis of New Dialkylphosphorylhydrazones

A series of 22 dialkylphosphorylydrazones (dialkyl ester, N′-[(1E)-(R1 phenyl)methylene]-phosphorohydrazidic acid), 20 of them new, along with three new N,N′-bis (diisobutylphosphorylthioamide)diamines (bis-[diisobutyl ester), N-thioxomethylene]-, diamine)phosphora-midic acid, were prepared and characterized by IR, 1H NMR, 13C NMR, 31P NMR, and mass spectrometry. The analysis of 1H NMR, 13C NMR, 31P NMR, and NOE spectra confirmed the observation of the single diastereoisomer E in the synthesis of dialkylphosphorylydrazones. The results of a molecular modeling study performed in order to investigate the mechanism of the synthesis of dialkylphosphorylydrazones are in agreement with the experimental results, i.e., the favored formation of diastereoisomer E over Z.

Chromones from Licania arianeae (Chrysobalanaceae)

The phytochemical studies of the leaves of Licania arianeae Prance (Crysobalanaceae) have led to the identification of ten new chromones, four 5,7-dihydroxy-2-alkylchromones, four 5,7-dihydroxy-6-chloro-2-alkylchromones and two 5,7-dihydroxy-6,8-dichloro-2-alkylchromones. The structures were established from IR, NMR and FAB-MS spectra data including 2D NMR experiments of natural substances and of the methyl derivatives.