Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 11 )

2019 ( 827 )

2018 ( 1094 )

2017 ( 1071 )

Custom range...

Search Results: 1 - 10 of 591727 matches for " L. Y. Vargas-Méndez "
All listed articles are free for downloading (OA Articles)
Page 1 /591727
Display every page Item
L. Y. Vargas-Méndez,V. V. Kouznetsov
Universitas Scientiarum , 2007,
Abstract: The piperidine compounds from natural or synthetic origin are of a great scientific interest due to his widestatus of biological activities: analgesic, neuroleptic, neurotropic, etc. Chemical and pharmacologicalproperties of the piperidine ring, including 4-aminopiperidines and spiro-4-piperidines are discussed inthis paper.
Challenges and Perspectives of Chemical Biology, a Successful Multidisciplinary Field of Natural Sciences
Fernando A. Rojas-Ruiz,Leonor Y. Vargas-Méndez,Vladimir V. Kouznetsov
Molecules , 2011, DOI: 10.3390/molecules16032672
Abstract: Objects, goals, and main methods as well as perspectives of chemical biology are discussed. This review is focused on the fundamental aspects of this emerging field of life sciences: chemical space, the small molecule library and chemical sensibilization (small molecule microassays).
Identification and Quantification of Monosaccharides in Aloe vera Gel by Acid and Enzymatic Hydrolysis and Wet Heat Treatment  [PDF]
Dianeli Madera Pi?a, Carlos Hernán Herrera Méndez, Lourdes Vargas y Vargas, Herbert Loria Sunza, Jorge Tamayo Cortez
Food and Nutrition Sciences (FNS) , 2017, DOI: 10.4236/fns.2017.88060
Abstract: Aloe vera (Aloe barbadensis Miller) possesses curative and therapeutic properties attributed to the polysaccharides found in its tissue. This work aimed to study hydrolyzed (chemical and enzymatical) Aloe vera gel extracts using ultrafiltration membranes with a pore size of 0.22 micron (μm). Nine chemical treatments were achieved with H2SO4 and three wet heat treatments were carried out at a pressure of 1.2 lbf/in2 for 15 minutes; in both cases, three different concentrations of Aloe vera gel juice (AGJ) were used: 1.5%, 2.5% and 3.5% w/w. The concentrations of H2SO4 were 0.10%, 0.25% and 0.40% w/w. Chemical experiments are performed over a factorial 32 design and results were analyzed using SPSS software (version 17, SPSS Inc.), finding the one labeled T7 (15 ml of AGJ 3.5% with 15 ml of H2SO4 0.10% added) the best of them, as it leaded to 0.0446 mg/ml of liberated glucose. Among the three wet heat treatments, the one labeled TC3 (15 ml of AGJ 3.5% with 15 ml of H2O added) was the best-performing one, as it leaded to 0.292 mg/ml of liberated glucose. Furthermore, an enzymatic hydrolysis was carried out using Novozymes’ Pectinex? AR and Viscozyme?. Hydrolisis with both enzymes yield to better results than acid hydrolysis: in the treatment with Pectinex? AR, 3.282 mg/ml of liberated glucose were obtained and 3.302 mg/ml in the treatment with Viscozyme?. The hydrolyzed substances obtained by acid and enzymatic hydrolysis, as well as by wet heat treatment, were subsequently analyzed by thin layer chromatography (TLC), using glucose, galactose and arabinose 1000 ppm solutions as reference patterns. Among the treatments by H2SO4, the one labeled T4 obtained an Rf value of 50, the same as on the galactose reference pattern.
Determinación de la estabilidad genética en cuatro especies del banco de germoplasma de papa en Cuba conservadas In Vitro
Castillo,J. G; Vargas,Dania; Estévez,Ana; Hernández,María M; Salomón,J. L; Pérez,Aymara; Borrás-Hidalgo,O; López,Y; Arencibia,A. D;
Cultivos Tropicales , 2010,
Abstract: four in vitro-preserved potato species were studied for ten years, with the aim of determining if they kept their genetic stability when compared to those from the base collection remaining in the field. species of both origins were morphologically described; isozymatic and molecular methods were used to evaluate if changes took place in the band patterns of in vitro-preserved species. the isozymatic systems, peroxidases, esterases, polyphenol oxidases and carbon anhydrase, and the aflp molecular marker were employed. the four preserved species used were: solanum schruteri buk, solanum dolichostigma buk, solanum jamesii jorr and solanum tuberosum l. seedlings were preserved in a slow growth medium and sub-cultivated twice a year. the qualitative characters, yield and its components were evaluated, to determine if there were phenotypical changes among the species studied. five primer combinations were used in the aflp analysis. a t test of media comparison was made to yield and its components, to calculate if there were differences among accessions. there were not any remarkable phenotypical changes for the qualitative characters, yield and its components. isozymatic systems did not detect changes in the band patterns, while aflp analysis showed notable differences concerning band number; thus, it is concluded that genetic stability is not maintained in the different species studied during the preservation period evaluated.
Purification and Partial Characterization of Polyphenol Oxidase from Sapodilla Plum (Achras sapota)  [PDF]
Jorge Tamayo Cortez, Carlos Hernán Herrera Méndez, Enrique Sauri Duch, María de Lourdes Vargas y Vargas, Sara Solís Pereira
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.47093
Abstract: The browning of fruits can be considered as an enzymatic oxidation which is believed to be one of the main causes of quality loss during post-harvest handling. The enzymes responsible for this are the oxidoreductases; the polyphenol oxidase (PPO) (monophenol, o-diphenol, oxygen oxidoreductase; EC belongs to this group. This enzyme, which is found in the sapodilla plum (Achras sapota), was purified using a phenylsepharose and a SephacrylS-200 columns. The molecular weight of the purified enzyme was estimated to be about 66 kDa by gel filtration and 29 kDa by SDS-PAGE. A single protein band was found using the latter system (SDS-PAGE), which shows that the PPO of the pulp of the sapodilla plum may be composed of two protein subunits with similar molecular weight. The optimum pH was 7.0 and the optimum temperature 60. The most effective inhibitors tested were ascorbic acid, sodium metabisulfite and acetic acid.
Efecto del peso molecular del ácido poliacrílico y de la relación SiO2/Al2O3 en el vidrio sobre la resistencia mecánica de cementos de polialqueonato vítreo
Vargas, G.,Rivera, H.,López, J.,Méndez, J.
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2002,
Abstract: Glass-polyalkenoate cements are widely used for dental applications. To better understand the processes involved in the formation reactions of this kind of cements and in order to explore their use in orthopedic applications, in the present work a study was carried out to analyze the effect of polyacrylic acid molecular weight and that of the SiO2/Al2O3 ratio in the glass on the compression strength and microstructural characteristics of glass-polyalkenoate cements. The produced samples were subjected to compression tests as well as to scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) analyses. An initial experimental series considered mean polyacrylic acid molecular weights of 2000, 9700, 15268 and 64000, keeping a constant SiO2/Al2O3 ratio of 2,5. A second experimental series considered SiO2/Al2O3 ratios of 2,1; 1,67; 1,25; 0,95 and 0,8; using polyacrylic acid having a constant molecular weight of 64000. The maximum compression strength (82,5 MPa) was achieved for a polyacrylic acid molecular weight of 64000 and a SiO2/Al2O3 ratio equal to 1. These compression strength values for glass-polyalkenoate cements are similar to those reported for polymethylmetacrylate-based cements, which suggests their potential use in orthopedic applications. Finally, the glass reactivity and the presence of unreacted –COOH functional groups were qualitatively evaluated by FTIR. Phase separation in glasses having SiO2/Al2O3 ratios > 1 as well as the surface reactivity of the glass particles were qualitatively evaluated by using Energy Dispersive Spectroscopy (EDX) on the SEM. In order to optimize the compression strength of glass-polyalkenoate cements, future work could be oriented toward the improvement of the glass reactivity, toward the optimization of the polymer/glass ratio and toward the use of nanometric glass particles. Los cementos de polialquenoato vítreo son ampliamente utilizados para aplicaciones dentales. Con el propósito de entender mejor los procesos involucrados en las reacciones de formación de este tipo de cementos y de explorar su uso en aplicaciones ortopédicas, en el presente trabajo se realizó un estudio para analizar el efecto del peso molecular del ácido poliacrílico y de la proporción sílice/ alúmina sobre la resistencia a la compresión y las características microestructurales de cementos de polialquenoato vítreo. Las probetas obtenidas fueron sometidas a pruebas de compresión y al análisis por microscopía electrónica de barrido (MEB) y por espectroscopía infrarroja por transformada de Fourier (IRTF). En una primera serie de expe
Main Polysaccharides Isolated and Quantified of Aloe vera Gel in Different Seasons of the Year  [PDF]
Berenice Aranda Cuevas, Carlos Hernán Herrera Méndez, Ignacio Islas Flores, Sara Solís-Pereira, Luis Cuevas-Glory, Gerardo Rivera Mu?oz, María de Lourdes Vargas y Vargas, Jorge Tamayo Cortez
Food and Nutrition Sciences (FNS) , 2016, DOI: 10.4236/fns.2016.76046
Abstract: We developed and implemented a methodology that allowed extracting and evaluating high molecular weight polysaccharides present in the gel of Aloe barbadensis Miller. One of the fractions evaluated revealed the presence of high molecular weight carbohydrates (200 kDa) with a behavior similar to that of acemannan and another fraction with compounds of molecular weights between 17 and 47 kDa. We quantified the concentration of acemannan for two different growing periods. The concentration of acemannan in the high molecular weight fraction was 99.97 ppm in the rainy season and 106.03 ppm in the dry season. The concentration of acemannan in the fraction of low molecular weight was 9.364 ppm during the season of greatest rainfall and 26.939 ppm in the dry season.
Synthesis of new 4-methyl-2-(4-pyridyl)-1,2,3,4-tetrahydroquinolines as potent antifungal compounds
Méndez, Leonor Y. Vargas;Zacchino, Susana A.;Kouznetsov, Vladimir V.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000100016
Abstract: synthesis, spectral characterization and biological results of new series of 2-(4-pyridyl)-1,2,3,4-tetrahydroquinolines and their closer precursors, -n-aryl-n-[1-(4-pyridyl)but-3-enyl]amines are reported. it was found that both γ-pyridyl substituted precursors and final products, tetrahydroquinolines, showed very good antifungal activities against aspergillus fumigatus, aspergillus flavus, aspergillus niger, microsporum gypseun, trichophyton rubrum and trichophyton mentagrophytes.
Journal of the Chilean Chemical Society , 2004, DOI: 10.4067/S0717-97072004000400010
Abstract: diverse n-(heteroarylmethyl)anilines were easily prepared from corresponding aldimines derived from commercially available aromatic aldehydes and anilines. new series of substituted nh-tetrahydroquinolines were also prepared using imino-diels-alder reaction between aldimines and n-vinylpyrrolidin-2-one in the presence of bf3.oet2 and the multi-component condensation reactions using a friendly ecological catalyst (bicl3). the secondary amines obtained bearing a heteroaryl moiety were tested as possible antibacterial and antifungal agents
Journal of the Chilean Chemical Society , 2004,
Abstract: Diverse N-(heteroarylmethyl)anilines were easily prepared from corresponding aldimines derived from commercially available aromatic aldehydes and anilines. New series of substituted NH-tetrahydroquinolines were also prepared using imino-Diels-Alder reaction between aldimines and N-vinylpyrrolidin-2-one in the presence of BF3.OEt2 and the multi-component condensation reactions using a friendly ecological catalyst (BiCl3). The secondary amines obtained bearing a heteroaryl moiety were tested as possible antibacterial and antifungal agents
Page 1 /591727
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.