Clara Nogueiras
University of Havana
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Publication
Featured researches published by Clara Nogueiras.
Journal of Chemical Ecology | 2010
Francisco A. Macías; Rodney Lacret; Rosa M. Varela; Clara Nogueiras; José M. G. Molinillo
A study was carried out on the allelopathic potential of four forest species, Tectona grandis, Aleurites fordii, Gliricidia sepium, and Maytenus buxifolia. The most active species, T. grandis, was selected to perform a phytochemical study. A new compound, abeograndinoic acid, was isolated, and elucidation of its structure showed that this compound has an unusual carbon skeleton. A further 21 known terpenoids—including 4 sesquiterpenoids, 8 diterpenes and 9 triterpenes—also were isolated. A biosynthetic scheme for the presence of the new compound is proposed. Bioactivity profiles that used etiolated wheat coleoptiles and phytotoxicity bioassays on the isolated compounds were conducted. The compounds that presented the highest phytotoxic activity are the diterpenes 9 (2-oxokovalenic acid) and 12 (19-hydroxyferruginol).
Phytochemistry | 2008
Francisco A. Macías; Rodney Lacret; Rosa M. Varela; Clara Nogueiras; José M. G. Molinillo
The bioactive fractions of Tectona grandis have yielded seven apocarotenoids, two of which have been isolated for the first time as natural products (tectoionols A and B). The chemical structures were determined through 1D and 2D nuclear magnetic resonance experiments. The absolute configuration of tectoionol A was determined using a modified Mosher methodology. Some NMR assignments for the compounds 9(S)-4-oxo-7,8-dihydro-beta-ionol and 3beta-hydroxy-7,8-dihydro-beta-ionone have been corrected on the basis of g-HSQC and g-HMBC experiments. The general bioactivities of isolated compounds have been studied using etiolated wheat coleoptiles. Those compounds that presented higher levels of activity were assayed on standard target species (Lactuca sativa, Lycopersicum esculentum, Lepidium sativum and Allium cepa).
Journal of Chemical Ecology | 2011
Rodney Lacret; Rosa M. Varela; José M. G. Molinillo; Clara Nogueiras; Francisco A. Macías
Two new quinones, (an isoprenoid quinone, and a dimeric anthraquinone) named naphthotectone and anthratectone, respectively, were isolated from bioactive leaf extracts from Tectona grandis. Their structures were determined by a combination of 1D and 2D NMR techniques. The bioactivity profile of naphthotectone was assessed using the etiolated wheat coleoptiles bioassay in aqueous solutions at concentrations ranging from 10−3 to 10−5M, as well as the standard target species lettuce, cress, tomato, and onion. Naphthotectone showed high level of activities in both bioassays. This fact, along with the presence of this compound as the major component in Tectona grandis, suggests that it may be involved in the allelopathic activity previously described for this species, and probably in other defense mechanisms.
Magnetic Resonance in Chemistry | 2010
Francisco A. Macías; José O. Guerra; Ana M. Simonet; Andy J. Pérez; Clara Nogueiras
A careful NMR analysis, especially by 1D TOCSY and 1D ROESY, of a refined saponin fraction allowed us to determine the structure of three saponins from a polar extract of Agave brittoniana Trel. spp. Brachypus leaves. The use of 1D DOSY for the suppression of the solvent signal was useful to obtain the chemical shifts of anomeric signals. A full assignment of the 1H and 13C spectral data for the new saponins, agabrittonosides E–F (1–2) and the well‐known Karatavioside C (3) and their methoxyl derivatives, is reported. The structures were established using a combination of 1D and 2D (1H, 1H‐COSY, TOCSY, ROESY, g‐HSQC, g‐HMBC and g‐HSQC‐TOCSY) NMR techniques and ESI–MS. In addition, the methoxylation of these furostane saponins in the presence of MeOH was studied. Copyright
World Journal of Microbiology & Biotechnology | 2014
Grolamys Castillo; Alejandro Torrecillas; Clara Nogueiras; Georgina Michelena; José Sánchez-Bravo; Manuel Acosta
Fermentation broth and biomass from three strains of Botryodiplodia theobromae were characterized by high performance liquid chromatography–electrospray tandem mass spectrometry (HPLC–ESI–MS/MS) method, in order to quantify different phytohormones and to identify amino acid conjugates of jasmonic acid (JA) present in fermentation broths. A liquid–liquid extraction with ethyl acetate was used as sample preparation. The separation was carried out on a C18 reversed-phase HPLC column followed by analysis via ESI–MS/MS. The multiple reaction monitoring mode was used for quantitative measurement. For the first time, indole-3-acetic acid, indole-3-propionic acid, indole-3-butyric acid and JA were identified and quantified in the ethyl acetate extracts from the biomass, after the separation of mycelium from supernatant. The fermentation broths showed significantly higher levels of JA in relation to the other phytohormones. This is the first report of the presence of gibberellic acid, abscisic acid, salicylic acid and the cytokinins zeatin, and zeatin riboside in fermentation broths of Botryodiplodia sp. The presence of JA-serine and JA-threonine conjugates in fermentation broth was confirmed using HPLC-ESI tandem mass spectrometry in negative ionization mode, while the occurrence of JA-glycine and JA-isoleucine conjugates was evidenced with the same technique but with positive ionization. The results demonstrated that the used HPLC–ESI–MS/MS method was effective for analysing phytohormones in fermentation samples.
Química Nova | 2011
Erik L. Regalado; Abilio Laguna; Judith Mendiola; O. Thomas; Clara Nogueiras
Bioguided fractionation of Agelas cerebrum crude extract resulted in isolation of four bromopyrrole and four bromopyrrole aminoimidazole alkaloids, identified as 5-bromopyrrole-2-carboxylic acid (1), 4-bromopyrrole-2-carboxylic acid (2), 3,4-bromopyrrole-2-carboxylic acid (3), 4,5-bromopyrrole-2-carboxylic acid (4), oroidin (5), bromoageliferin (6), dibromoageliferin (7) and dibromosceptrin (8) on the basis of spectroscopic data analyses (UV, IR, HRMS, 1D and 2D NMR) and comparison with literature data. This is the first report of compounds 2 and 3 in a marine sponge belonging to the Agelas genus and the first evidence of the presence of 1 from a natural source.
Química Nova | 2007
Erik L. Regalado; Abilio Laguna; Mabel Torres; Juan D. Sabatier; Margarita Hernández; Anselmo E. Ferrer; Clara Nogueiras
Hydrogen peroxide bleaching of sodium alginate from seaweeds oh the Sargassum genus was studied. The influence of H2O2 concentration (percentage of H2O2 on a dry weight alginate basis, w/w) and NaOH/H2O2 ratio (% NaOH/% H2O2, both referred to a dry weight alginate basis, w/w) on the molecular weight, color removal and content of Fe3+ ions of bleached alginate samples was investigated by UV and IR spectroscopies, colorimetric determination of Fe3+ ions and vapor pressure osmometry. Higher yield, purity and molecular weight of alginate were obtained using 3% (or less) of hydrogen peroxide and a NaOH/H2O2 ratio of 1.2 for bleaching.
Marine Biotechnology | 2009
Erik L. Regalado; María Cecilia Rodríguez; Roberto Menéndez; Ángel Concepción; Clara Nogueiras; Abilio Laguna; Armando A. Rodríguez; David E. Williams; Patricia Lorenzo-Luaces; Olga Valdés; Yasnay Hernández
Tetrahedron | 2011
Erik L. Regalado; Carlos Jiménez-Romero; Grégory Genta-Jouve; Deniz Tasdemir; Philippe Amade; Clara Nogueiras; O. Thomas
Revista De Biologia Tropical | 2007
José O. Guerra; Alfredo Meneses; Ana M. Simonet; Francisco A. Macías; Clara Nogueiras; Alicia Gómez; José A. Escario