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Dive into the research topics where Mercedes Jiménez-Atiénzar is active.

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Featured researches published by Mercedes Jiménez-Atiénzar.


Journal of Agricultural and Food Chemistry | 2010

Stabilization of the bioactive pigment of Opuntia fruits through maltodextrin encapsulation.

Fernando Gandía-Herrero; Mercedes Jiménez-Atiénzar; Juana Cabanes; Francisco García-Carmona; Josefa Escribano

Betalains are water-soluble, nitrogen-containing pigments of growing interest in the food industry. They are present in most plants belonging to the order Caryophyllales, where they fulfill the role of anthocyanins, and are divided into two groups: violet betacyanins and yellow betaxanthins. They are bioactive molecules that account for health-promoting properties, recently described for cactus pears (Opuntia). In this work, the characteristic betalain of cactus pears, indicaxanthin, is obtained purely, and its stability is highly promoted by its encapsulation in a maltodextrin matrix. A suitable spray-drying procedure for encapsulation is described, and a bright yellow powder is obtained. The stability is analyzed under different conditions. In the absence of light, pure encapsulated pigment can be stored at 20 °C for months without appreciable loss of the bioactive substance and color variation. Furthermore, free radical scavenging and antioxidant properties of the pigment are studied under the ABTS(•+) radical and ferric reducing antioxidant power assays, in the presence and in the absence of maltodextrins. The stabilization of pure betalain pigments may boost the use of these bioactive and natural coloring molecules.


Biological Chemistry | 2005

Evidence for a common regulation in the activation of a polyphenol oxidase by trypsin and sodium dodecyl sulfate.

Fernando Gandía-Herrero; Mercedes Jiménez-Atiénzar; Juana Cabanes; Francisco García-Carmona; Josefa Escribano

Abstract Polyphenol oxidase (PPO) was extracted from beet root, in both soluble and membrane fractions, and in both cases the enzyme was in a latent state. PPO from the membrane fraction showed no diphenolase activity unless it was activated by trypsin or sodium dodecyl sulfate (SDS). The kinetics of the activation process of latent PPO by trypsin was studied and the specific rate constant of active PPO formation, k 3, showed a value of 0.03 s−1. The protease-activated form showed a pH optimum (6.5) and kinetic properties identical to those of the SDS-activated enzyme. Evidence is provided for the existence of a common peptide responsible for the regulation of the activity of the enzyme by both proteolysis and SDS detergent. Formation of the active proteolyzate was followed by spectroscopic measurements, Western blotting and partially denaturing SDS-PAGE.


Journal of Agricultural and Food Chemistry | 2009

Fluorescence detection of tyrosinase activity on dopamine-betaxanthin purified from Portulaca oleracea (common purslane) flowers.

Fernando Gandía-Herrero; Mercedes Jiménez-Atiénzar; Juana Cabanes; Josefa Escribano; Francisco García-Carmona

Tyrosinase or polyphenol oxidase (EC 1.14.18.1) is one of the key enzymes for the biosynthesis of natural pigment betalains. These are an important class of water-soluble pigments, characteristic of plants belonging to the order Caryophyllales. In this work, dopamine-betaxanthin (also known as miraxanthin V) is reported as the pigment responsible for the bright coloration in yellow flowers of Portulaca oleracea (common purslane). The natural pigment is purified, and used as a substrate for the catecholase (diphenolase) activity of the enzyme tyrosinase. A new, continuous method to follow the activity is developed based on the fluorescent properties of the betaxanthin. Fluorescence of the enzyme activity derived products is reported for the first time. Relevance of the fluorescent phenomenon is discussed based on fluorescence images and the description of a physiological inner filter effect present in flowers of P. oleracea. The first description of the betalain content in flower pistils is also provided.


Food Chemistry | 2017

Characterization of betalains, saponins and antioxidant power in differently colored quinoa (Chenopodium quinoa) varieties

Josefa Escribano; Juana Cabanes; Mercedes Jiménez-Atiénzar; Martha Ibañez-Tremolada; Luz Rayda Gomez-Pando; Francisco García-Carmona; Fernando Gandía-Herrero

Quinoa was the traditional grain crop used by the prehispanic civilizations in America. Grains are white, black, yellow, and red-violet and plants are cultivated in vast areas of Peru, Bolivia and Ecuador. The recent description of the betacyanin pigment betanin in red-violet varieties is here further analyzed detecting the presence of amaranthin not previously identified in quinoa grains. Yellow-orange grains are characterized for the first time and up to four different betaxanthins are found to be responsible for this coloration. The native fluorescence of the identified betaxanthins makes the surface of the yellow quinoa grains glow with green fluorescent light. The presence of betalains is correlated with high antioxidant and free radical scavenging activities measured under the FRAP, ABTS and ORAC assays in grain extracts of 29 Peruvian varieties. TEAC equivalence is as high as 44.1 and 47.4mmol Trolox/kg for the yellow and red-violet varieties analyzed respectively.


Journal of Agricultural and Food Chemistry | 2014

One-Step Synthesis of Betalains Using a Novel Betalamic Acid Derivatized Support

Juana Cabanes; Fernando Gandía-Herrero; Josefa Escribano; Francisco García-Carmona; Mercedes Jiménez-Atiénzar

Betalains are plant pigments with high antioxidant and cancer chemopreventive properties used by the food industry as safe colorants. Betalains are restricted to species of the order Caryophyllales, and difficulty in obtaining individual molecules has limited their structural identification and application. This study was designed to develop a betalamic acid derivatized support generated from a primary amine polymer. The novel material presents color properties of a pseudobetaxanthin, and it is stable for at least 6 months. The bond formed can be displaced at mild conditions by the addition of amines in aqueous solutions over a broad pH range and at 25 °C. This releases the betalamic acid while forming the corresponding pigment. This one-step procedure significantly simplifies the process of obtaining semisynthetic betalains, and it is optimized here for the formation of betaxanthins and betacyanins derived from tyramine, dopamine, pyrrolidine, and indoline. The new method makes access to single betalains available to the entire scientific community and could stimulate research and applications in the field.


Biochemical and Biophysical Research Communications | 2004

Kinetic analysis of catechin oxidation by polyphenol oxidase at neutral pH.

Mercedes Jiménez-Atiénzar; Juana Cabanes; Fernando Gandía-Herrero; Francisco García-Carmona


Journal of Agricultural and Food Chemistry | 2013

Encapsulation of the Most Potent Antioxidant Betalains in Edible Matrixes as Powders of Different Colors

Fernando Gandía-Herrero; Juana Cabanes; Josefa Escribano; Francisco García-Carmona; Mercedes Jiménez-Atiénzar


Journal of Agricultural and Food Chemistry | 2007

Partial Purification of Latent Polyphenol Oxidase from Peach (Prunus persica L. Cv. Catherina). Molecular Properties and Kinetic Characterization of Soluble and Membrane-Bound Forms

Juana Cabanes; Josefa Escribano; Fernando Gandía-Herrero; Francisco García-Carmona; Mercedes Jiménez-Atiénzar


Journal of Agricultural and Food Chemistry | 2005

Differential activation of a latent polyphenol oxidase mediated by sodium dodecyl sulfate

Fernando Gandía-Herrero; Mercedes Jiménez-Atiénzar; Juana Cabanes; Francisco García-Carmona; Josefa Escribano


Plant Physiology and Biochemistry | 2005

Oxidation of the flavonoid eriodictyol by tyrosinase.

Mercedes Jiménez-Atiénzar; Josefa Escribano; Juana Cabanes; Fernando Gandía-Herrero; Francisco García-Carmona

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