RESUMO
A set of alkyl aluminum complexes supported by non-symmetric ferrocenyl amidine ligands were used as catalysts for the preparation of cyclic carbonates from epoxides and carbon dioxide using Bu4NI as a co-catalyst. A modified method for the synthesis of aminoferrocene allowed us to obtain this precursor in quantitative yield. Treatment of aminoferrocene with the corresponding acetimidoyl chloride afforded the desired ferrocenyl amidine ligands L1H, (E)-N-(2,6-diisopropylphenyl)-N'-(ferrocenyl)acetimidamide, and L2H, (E)-N-(2,6-dimethylphenyl)-N'-(ferrocenyl)acetimidamide. The reaction of these ligands with 1.0 or 0.5 equiv. of AlMe3 led to the synthesis of aminoferrocene based aluminum complexes ((L1)AlMe2 (1), (L2)AlMe2 (2), (L1)2AlMe (3), and (L2)2AlMe (4)) in excellent yields, which were characterized by spectroscopic and X-ray diffraction methods. In addition, we have studied their electrochemical properties and complex 1 was found to be the most active catalyst for the formation of cyclic carbonates 6a-j from their corresponding epoxides 5a-j and CO2.
RESUMO
Introducción: el frijol además de ser una fuente nutricional importante en Colombia, también aporta un gran contenido de sustancias con potencial benéfico para la salud, como son flavonoides y antocianinas, entre otras, que contribuyen de manera significativa con sus propiedades medicinales y pueden tener un efecto positivo contra algunas enfermedades crónicas. Objetivos: comparar el contenido de antocianinas del pericarpio del fruto de frijol de diferentes variedades con respecto al método de extracción. Métodos: la piel del fruto de frijol deshidratada y macerada se sometió a extracciones sólido-líquido y asistida por microondas con metanol acidulado. Se evaluó el contenido de antocianinas por el método de diferencial de pH y el potencial antioxidante in vitro con base en el método de DPPH (catión radical α-α-difenil-ß-picrilhidrazilo). Resultados: la técnica de extracción asistida por microondas (MAE) mostró una mayor eficiencia respecto a la convencional, porque disminuyó considerablemente la cantidad de solvente, de muestra empleada y los tiempos de extracción. Los extractos obtenidos presentaron un contenido de antocianinas entre 8,33 y 25,5 mg cianidin-3-glucósido/L, sin embargo, el efecto de protección antioxidante resultó similar entre ellos y comparable con el de las sustancias de referencia. Conclusiones: todos los extractos presentaron buena capacidad protectora contra radicales libres; la técnica de extracción asistida por microondas puede ser usada como método alternativo para una valoración rápida, eficiente y eficaz del contenido de sustancias bioactivas en diferentes matrices.
Introduction: apart from being an important nutritional source in Colombia, beans also provide a large amount of substances with potential beneficial effects on health, such as flavonoids and anthocyanins, among others, which stand out for their medicinal properties and potential positive action against some chronic diseases. Objectives: compare the content of anthocyanins in the pericarp of the fruit of different varieties of beans with reference to the extraction method. Methods: after dehydration and maceration, the bean fruit coat was subjected to solid-liquid and microwave assisted extraction with acidulated methanol. Anthocyanin content was determined by the pH differential method, and the cation radical α-α-diphenyl-ß-picrylhydrazyl (DPPH) method was used for determination of in vitro antioxidant potential. Results: microwave assisted extraction (MAE) proved to be more efficient than the conventional technique, with a considerable reduction in the amount of solvent, sample and extraction time. Anthocyanin content in the extracts obtained was between 8.33 and 25.5 mg cyanidin-3-glucoside/L. However, their antioxidant protection effect was similar and comparable to that of reference substances. Conclusions: all extracts showed good protective capacity against free radicals. Microwave assisted extraction may be used as an alternative method for fast, efficient and effective evaluation of the content of bioactive substances in various matrices.
