Consulta: subjectFacets:"13C NMR"
Registros recuperados: 3
Data/hora: 03/06/2024 15:33:09

13C NMR spectral data and molecular descriptors to predict the antioxidant activity of flavonoids
Provedor de dados: Brazilian Journal of Pharmaceutical Sciences
Autores: Scotti,Luciana; Fernandes,Mariane Balerine; Muramatsu,Eric; Emereciano,Vicente de Paula; Tavares,Josean Fechine; Silva,Marcelo Sobral da; Scotti,Marcus Tullius.
Tissue damage due to oxidative stress is directly linked to development of many, if not all, human morbidity factors and chronic diseases. In this context, the search for dietary natural occurring molecules with antioxidant activity, such as flavonoids, has become essential. In this study, we investigated a set of 41 flavonoids (23 flavones and 18 flavonols) analyzing their structures and biological antioxidant activity. The experimental data were submitted to a QSAR (quantitative structure-activity relationships) study. NMR 13C data were used to perform a Kohonen self-organizing map study, analyzing the weight that each carbon has in the activity. Additionally, we performed MLR (multilinear regression) using GA (genetic algorithms) and molecular...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Flavonoids/antioxidant activity; 13C NMR; Kohonen self-organizing map.
Ano: 2011
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-82502011000200005

CHARACTERIZATION OF BULK SOIL HUMIN AND ITS ALKALINE-SOLUBLE AND ALKALINE-INSOLUBLE FRACTIONS
Provedor de dados: Revista Brasileira de Ciência do Solo
Autores: Li,Cuilan; Gao,Shuqing; Gao,Qiang; Wang,Lichun; Zhang,Jinjing.
Humic substances are the major components of soil organic matter. Among the three humic substance components (humic acid, fulvic acid, and humin), humin is the most insoluble in aqueous solution at any pH value and, in turn, the least understood. Humin has poor solubility mainly because it is tightly bonded to inorganic soil colloids. By breaking the linkage between humin and inorganic soil colloids using inorganic or organic solvents, bulk humin can be partially soluble in alkali, enabling a better understanding of the structure and properties of humin. However, the structural relationship between bulk humin and its alkaline-soluble (AS) and alkaline-insoluble (AIS) fractions is still unknown. In this study, we isolated bulk humin from two soils of...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Soil humic substances; Humin fractionation; Elemental composition; 13C NMR.
Ano: 2015
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832015000100120

Contribution of humic substances from different composts to the synthesis of humin in a tropical soil
Provedor de dados: Revista Brasileira de Ciência do Solo
Autores: Lima,Claudivan Costa; Mendonça,Eduardo de Sá; Roig,Asunción.
The contribution of humic substances of different composts to the synthesis of humin in a tropical soil was evaluated. Increasing doses (0, 13, 26, 52, and 104 Mg ha-1) of five different composts consisting of agroinpowderrial residues were applied to a Red-Yellow Latosol. These composts were chemically characterized and 13C NMR determined and the quantity of the functional alkyl groups of humic acids applied to the soil as compost was estimated. Thirty days after application of the treatments, organic matter samples were collected for fractionation of humic acids (HA), fulvic acids (FA) and humin (HU), from which the ratios HA/FA and (HA + FA)/HU were calculated. The application of the composts based on castor cake resulted in the highest HU levels in the...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Humic acids; Fulvic acids; 13C NMR; Alkyl groups; Recalcitrance.
Ano: 2010
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832010000400004