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Doñinos de Salamanca, Spain

Santos-Buelga C.,Grupo de Investigacion en Polifenoles | Mateus N.,University of Porto | De Freitas V.,University of Porto
Journal of Agricultural and Food Chemistry

Anthocyanins are plant pigments widespread in nature. They play relevant roles in plant propagation and ecophysiology and plant defense mechanisms and are responsible for the color of fruits and vegetables. A large number of novel anthocyanin structures have been identified, including new families such as pyranoanthocyanins or anthocyanin oligomers; their biosynthesis pathways have been elucidated, and new plants with "a la carte" colors have been created by genetic engineering. Furthermore, evidence about their benefits in human health has accumulated, and processes of anthocyanin absorption and biotransformation in the human organism have started to be ascertained. These advances in anthocyanin research were revised in the Seventh International Workshop on Anthocyanins that took place in Porto (Portugal) on September 9-11, 2013. Some selected papers are collected in this special issue, where aspects such as anthocyanin accumulation in plants, relationship with color expression, stability in plants and food, and bioavailability or biological activity are revised. © 2014 American Chemical Society. Source

Delgado L.,Grupo de Investigacion en Polifenoles | Fernandes I.,University of Porto | Gonzalez-Manzano S.,Grupo de Investigacion en Polifenoles | De Freitas V.,University of Porto | And 2 more authors.
Food and Function

Dietary flavonoids have been associated with a lower incidence of some chronic diseases. However, the mechanisms behind the in vivo biological activity of flavonoids are still mostly unknown. Flavonoids are metabolized in the human body to conjugated forms (methylated, sulphated and glucuronidated derivatives) that should play a role in flavonoid activity. In this study, the anti-proliferative effects of conjugated metabolites of quercetin and (epi)catechin, major flavonoids in the diet, have been evaluated against three different cancer cell lines from breast (MCF-7), colon (Caco-2) and pancreas (BxPC-3) and one normal cell line of human foreskin fibroblasts (HFF-1), and compared with the effect of their unconjugated forms. Quercetin showed anti-proliferative activity on the three assayed cell models, whereas catechin and epicatechin were not active. Methylation on ring-B of quercetin decreased the anti-proliferative effects, especially when the methylation occurred in position 3′ (isorhamnetin), although methylated metabolites still showed significant anti-proliferative activity. As to catechins, 4′-O-methyl- epicatechin and 3′-O-methyl-epicatechin were the only ones to show some activity on MCF-7 and BxPC-3 cell lines, respectively. Conjugation of quercetin with glucose or glucuronic acid eliminated the anti-proliferative effects of aglycones. Sulphated metabolites were also tested and found to be inactive in most of the explored cell lines, although quercetin-4′-O-sulphate and epicatechin-3′-O-sulphate still showed some anti-proliferative activity on MCF-7 and Caco-2 cells, respectively. This journal is © the Partner Organisations 2014. Source

Ferrer-Gallego R.,Grupo de Investigacion en Polifenoles | Goncalves R.,University of Porto | Rivas-Gonzalo J.C.,Grupo de Investigacion en Polifenoles | Escribano-Bailon M.T.,Grupo de Investigacion en Polifenoles | De Freitas V.,University of Porto
Food Chemistry

The ability of grape seed extracts to bind to bovine serum albumin (BSA) and α-amylase was studied by fluorescence quenching of protein intrinsic fluorescence and nephelometry. The influence of grape seed ripeness on astringency was also evaluated. From the spectra obtained, the modified Sterm-Volmer (Kapp) and the bimolecular quenching constants were calculated. Results showed that grape seed extracts had good affinity for proteins. The association strength of tannin-protein interactions varied with changes in tannin structure associated with the degree of ripeness affecting the binding/quenching process. In all cases studied, higher values of K app were obtained in samples at harvest which have greater ability to bind to proteins than have samples at post-veraison time. Nephelometric assays show the same trend as do fluorescence quenching studies. A possible explanation for this is that, as seeds ripen, their tannins increase in molecular mass, which relates to an increase in hydrophobicity of the molecules, and this increases protein affinity. However, that is contrary to the reported decrease in astringency of grape seeds during maturity. This indicates that tannin-protein interactions are not the only explanation for the complex sensations of astringency of grape seeds. © 2012 Elsevier Ltd. All rights reserved. Source

Ferrer-Gallego R.,Grupo de Investigacion en Polifenoles | Hernandez-Hierro J.M.,Food Colour and Quality Laboratory | Rivas-Gonzalo J.C.,Grupo de Investigacion en Polifenoles | Escribano-Bailon M.T.,Grupo de Investigacion en Polifenoles
Journal of Food Engineering

Grape seed and skin sensory parameters are important characteristics in making decisions concerning the optimal harvest time and producing high-quality red wines. The potential of near infrared spectroscopy to determine several sensory parameters of seeds and skins was evaluated. Taste (sourness), texture (astringency, tannic intensity, dryness and hardness), visual (colour) and olfactory (intensity and type of aroma) attributes were considered. Calibration models were performed by modified partial least squares regression. The differences between sensory analysis and NIRS analysis in external validation were lower in the case of seeds; they were between 4.5% for hardness and 8.7% for colour. For the skins, differences in external validation were between 9.8% for tannic intensity and 13.7% for astringency. The results obtained show that NIRS technology has considerable potential for predicting the above sensory attributes. © 2013 Elsevier Ltd. All rights reserved. Source

Garcia-Marino M.,Grupo de Investigacion en Polifenoles | Hernandez-Hierro J.M.,Grupo de Investigacion en Polifenoles | Rivas-Gonzalo J.C.,Grupo de Investigacion en Polifenoles | Escribano-Bailon M.T.,Grupo de Investigacion en Polifenoles
Analytica Chimica Acta

The Vitis vinifera L. cv Graciano is often used as an integral component of Rioja wines because it is considered to contribute significantly to the quality of Tempranillo based wines. The aim of this work was to determine the effect of the incorporation of the Graciano variety on the colour and pigment composition of Tempranillo based wine and to evaluate the possible differences between blending Tempranillo with Graciano varietal wine (W wine) in contrast to a wine obtained by mixing these two grape varieties in the prefermentative maceration step (M wine). Results indicated that pigment extraction and retention in M wine was higher than in Tempranillo (T) wine. Colour differences (Δ Eab *) between wines at the end of the study (after 12 months in bottles) were detectable by the human eye (Δ Eab * ≥ 3) in all cases except for T and W. These wines have indistinguishable colours even when using analytical methods (Δ Eab * ≤ 1). Regarding hue hab, T and W presented higher values (more orange-red) than Graciano (G) and M (more blue-red). PCA allowed the colour and composition analytical data to be reduced to a small number of principal components that could separate successfully between T and G wines and between the different steps of the winemaking process. © 2009 Elsevier B.V. All rights reserved. Source

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