Chemical composition and antioxidant-prooxidant potential of a polyphenolic extract and a proanthocyanidin-rich fraction of apple skin.

The apple is a food rich in diverse classes of polyphenols (PP), among which the proanthocyanidins (PCs), which are primarily concentrated in the skin, are one of the most abundant. These compounds are of considerable interest for their possible positive health effects because of their antioxidant properties. However, depending on the classes of PP present (chemical composition) and their relative concentrations in the apple skin, their antioxidant effects vary and some of their components can even generate prooxidant effects. This work determined the chemical composition and antioxidant-prooxidant potential of a polyphenolic extract (PPE) and a proanthocyanidin-rich fraction (PRF) of apple skin, along with the contribution of their most abundant individual compounds, based on their copper chelating ability, ease in reducing peroxidase-generated free radicals and TEAC (Trolox-Equivalent Antioxidant Capacity) assay. For this purpose, chromatographic and colorimetric methods were used. The majority compounds identified in PPE were flavan-3-ols (44.58%), flavonols (42.89%) and dihydrochalcones (11.60%). In PRF, we detected monomers and oligomers from dimers to heptamers, which were composed of 97% (-)-epicatechin and 3% (+)-catechin. The antioxidant potential was notably higher in PRF than in PPE. The (-)-epicatechin monomer and the procyanidin B2 dimer showed more ease in reducing peroxidase-generated free radicals compared to other compounds of the apple skin, whereas phloridzin dihydrochalcone produced prooxidant effects.

Computational study of the structure-free radical scavenging relationship of procyanidins.

Procyanidins (PCs) are effective free radical scavengers, however, their antioxidant ability is variable because they have different degrees of polymerisation, are composed by distinct types of subunits and are very susceptible to changes in conformation. In this work the structure-free radical scavenging relationship of monomers, dimers and trimers of PCs was studied through the hydrogen atom transfer (HAT), sequential proton-loss electron-transfer (SPLET) and single electron transfer followed by proton transfer (SET-PT) mechanisms in aqueous phase, employing the Density Functional Theory (DFT) computational method. The structure-free radical scavenging relationship of PCs showed a very similar behaviour in HAT and SET-PT mechanisms, but very different in the SPLET mechanism. The structural factor that showed more effects on the ability of PCs to scavenge free radicals in aqueous phase was the conformation.

Propiedades y posibles aplicaciones de las proteínas de salvado de trigo / Properties and application possibilities of wheat bran proteins

Resumen El salvado de trigo se destina principalmente al consumo animal, por lo que algunos de sus componentes son subutilizados, representando oportunidades de valor agregado. Constituye las capas externas del grano y contiene hasta 18 % en peso de proteínas con mejor calidad que las de la harina. Estas proteínas no son aprovechadas debido a que la mayoría están protegidas por una matriz de polisacáridos, indigerible para el sistema gastrointestinal humano, por lo que es necesaria su extracción. Tradicionalmente, las proteínas de salvado han sido recuperadas mediante extracción alcalina y se han propuesto como ingredientes para la elaboración de productos alimenticios. Sin embargo, su uso es casi inexistente, debido a que los procesos de extracción son agresivos y no redituables. El objetivo del presente trabajo fue describir las propiedades de las proteínas del salvado de trigo, así como sus usos potenciales. Entre sus propiedades destacan la digestibilidad, el perfil de aminoácidos y la capacidad de absorción de grasa. La fracción soluble en agua de estas proteínas, por su fácil extracción, podría tener valor agregado al utilizarse en tecnologías emergentes: como fuente de péptidos bioactivos, en la producción de nanopartículas con aplicaciones industriales o como matrices para procesos de biomineralización artificial.

Abstract Wheat bran is mainly intended for animal consumption and some of its components are underutilized, representing value-added opportunities. It forms the outer layers of the grain and contains up to 18 % by weight of proteins of better quality than those of flour. These proteins are not exploited because most are protected by a matrix of polysaccharides, which is indigestible by the human gastrointestinal system" so their extraction is necessary. Traditionally, wheat bran proteins have been recovered by alkaline extraction and have been proposed as ingredients for the manufacture of foodstuffs. However, their use is almost non-existent because the extraction processes are aggressive and not profitable. The aim of the present review is to present the proper ties of wheat bran proteins, as well as, their potential uses. Among their properties, the digestibility, lipid absorption capacity and aminoàcid pattern are highlighted. The water soluble fraction of these proteins, because of their easy extraction, could have an added value from the perspetive of emerging technologies, for example, as a source of bioactive peptides, in the production of nanoparticles with industrial applications or as matrices for artificial biomineralization processes.

Nanotubus de carbono y bionanotecnología / Carbon nanotubes and bionanotechnology

Los nanotubos de carbono (NTC) son estructuras artificiales novedosas que presentan propiedades físicas inusuales. Estas propiedades han hecho a los NTC objeto de una gran cantidad de estudios, los cuales han revelado un inmenso potencial de aplicación en diferentes áreas, tales como la electrónica, la física y la biología. En este trabajo se revisan los conceptos básicos sobre la química, obtención y modificación de los NTC, y se discute su posible utilización en sistemas biológicos.