Search

espanolEste estudio determina la utilizacion de mapas conceptuales como tecnica de analisis de libros de texto de calculo diferencial, con el objeto de identificar los obstaculos epistemologicos sobre la nocion derivada. La investigacion se centra en los postulados de mapa conceptual de Novak y Canas y el significado holistico de la derivada. La metodologia es descriptiva, pues se disena un mapa conceptual para la nocion derivada y se contrasta con los elementos que se abordan para la ensenanza de la nocion en un libro de texto de calculo diferencial. Los resultados obtenidos muestran representaciones y conceptos asociados a la derivada que el autor del texto no aborda, evidenciando la falta de estructura para potenciar el aprendizaje de la nocion de derivada. EnglishThis study determines the use of concept maps as technical analysis textbooks of differential calculus, akin to identify some epistemological obstacles on the derivative notion. The research focuses on the principles of conceptual map of Novak and Canas (2008) and the holistic meaning of the derivative. The methodology is descriptive, designed as a conceptual map for the derivative concept and it is compared with the elements that are addressed to teaching the concept in a textbook of differential calculus. The results show representations and concepts associated with the derivative that the author of the textbook does not address, highlighting the lack of structure to enhance learning of the notion of derivative.

A bio-guided study of leaf extracts allowed the isolation of two new macrobicyclic hydrolysable tannins, namely merianin A (1) and merianin B (2), and oct-1-en-3-yl &beta, xylopyranosyl-(1&rdquo, 6&rsquo, )-&beta, glucopyranoside (3) from Meriania hernandoi, in addition to 11 known compounds reported for the first time in the Meriania genus. The structures were elucidated by spectroscopic analyses including one- and two-dimensional NMR techniques and mass spectrometry. The bioactivities of the compounds were determined by measuring the DPPH radical scavenging activity and by carrying out antioxidant power assays (FRAP), etiolated wheat coleoptile assays and phytotoxicity assays on the standard target species Lycopersicum esculentum W. (tomato). Compounds 1 and 2 exhibited the best free radical scavenging activities, with FRS50 values of 2.0 and 1.9 &micro, M, respectively.

Two new flavonol glycosides were isolated from the leaves of Siparuna gigantotepala. Their structures were determined to be kaempferol 3-O-β-xylopyranosyl-(1→2)-α-arabinofuranoside (1) and kaempferol 3,7-di-O-methyl-4'-O-α-rhamnopyranosyl-(1→2)-β-glucopyranoside (2). In addition, three known flavonol glycosides, rutin (3), kaempferol 3-O-rutinoside (4), and kaempferol 3,7-di-O-methyl-4'-O-rutinoside (5), and three flavonol aglycones, quercetin (6), kaempferol 3,7-dimethyl ether (7), and kaempferol 3,7,4'-trimethyl ether (8), were also isolated and are reported here for the first time in this species. The structures of compounds 1 and 2 were established on the basis of their LC-MS and one- and two-dimensional (1D)- and (2D)-NMR spectroscopic analyses, combined with acid methanolysis and silylation of sugar moieties for GC-MS. Evaluation of the antioxidant activity, conducted in the 96-well plate format, showed that the flavonoids isolated possess strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and moderate oxygen radical absorption capacity.

Summary Objective: This study analyzes the frequency of palatal rugae on young scholars of two Colombian populations. Besides determines the variability, the sexual dimorphism and the bilateral symmetry of the palatal rugae. Materials and Methods: A descriptive study analyzes palatal rugae through Trobo’s method in 208 dental casts chosen by convenience, 112 of Cali racially mixed population (46 females and 66 males) with ages between the 10 and 18 years old; and 96 of Colombian Amazons natives (53 females and 43 males) with ages between the 5 and 12 years old. Results: The line, wavy and curve palatal rugae features showed high frequency in both sexes and in ethnic groups. The forms angle and circle showed low frequency. Sexual dimorph and bilateral symmetry were not evidenced. Differences between the distribution of the primary and derivatives palatal rugae according to the ethnic group were also not evident. Conclusions: According to the frequency, shape and disposition of primary and derived palatal rugae, they do not evidence sexual dimorphism and bilateral symmetry. Line, sinuous and curve were the most frequent shapes, for primary and derived rugae. There were no identical rugograms between subjects, which conferes to the rugae the characteristic of unique, then rugae can be useful in forensic identification. Key words: Forensic sciences. Forensic dentistry. Dentistry identification. Palatal rugae. Rugoscopy.

Tithonia diversifolia, Asteraceae, a promising alternative for insect control such as leaf-cutting ants, have revealed repellent and insecticidal activity against Atta cephalotes. The different biological activities of T. diversifolia, are due to the existence of sesquiterpene lactones and phenolic compounds. Some phenolic compounds have antioxidant activity and curiously also exhibited tyrosinase inhibitory activity, key enzyme in insect metamorphosis. To expand the plant phytochemical knowledge, especially for isolation and identification of secondary metabolites such as phenolic compounds not yet discovered in the polar extracts, a new caffeic acid derivative was isolated from the leaves of Tithonia diversifolia. The structure was determined as (E)-3-(((3-(3,4-dihydroxyphenyl)acryloyl)oxy)methyl)-2-methyloxyrane-2-carboxylic acid (1). Additionally, three known phenolic acids, 4,5-dicaffeoylquinic acid (2), 3,4-dicaffeoylquinic acid (3) and 3,5-dicaffeoylquinic acid (4), were also isolated; 1, 2 and 3 are the first reports for this species. The structures of compounds 1, 2 and 3 were established based on LC-MS and one- and two-dimensional (1D)- and (2D)-NMR spectroscopic analyses. Spectroscopic data of compound 1 were compared with 4-O-caffeoyl-2-C-methyl-d-threonic acid (5). Antioxidant activity evaluation in 96-well plate format, showed caffeic acid derivatives as strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavengers and moderate ferric reducing antioxidant power (FRAP).

In the 70s, reports began to appear of phenolic metabolites of brown algae with the characteristics of tannins; these compounds, initially termed phaeophyte tannins, marine algal polyphenols or polyphloroglucinols, are known as phlorotannins, the youngest group of plant polyphenolics. Despite over 40 years of research in phlorotannins, this area is still in the exponential growth phase; however, several reviews have appeared, primarily concerning their biological activity. This review focuses on techniques for the extraction, isolation and chromatographic purification of approximately 150 phlorotannins during these four decades. Due to the high structural diversity of these polyphenols and the difficulty of classification, these topics are also reviewed: structural diversity and classification, extraction and preparative chromatography, thin-layer chromatography, and analytical high-performance liquid chromatography (HPLC) and HPLC-mass spectrometry. These techniques have primarily been used for separation monitoring and qualitative profiles, and not too many reports have been published on the development of quantification or quality control.

Two new flavonol glycosides were isolated from the leaves of Siparuna gigantotepala. Their structures were determined to be kaempferol 3-O-β-xylopyranosyl-(1→2)-α-arabinofuranoside (1) and kaempferol 3,7-di-O-methyl-4'-O-α-rhamnopyranosyl-(1→2)-β-glucopyranoside (2). In addition, three known flavonol glycosides, rutin (3), kaempferol 3-O-rutinoside (4), and kaempferol 3,7-di-O-methyl-4'-O-rutinoside (5), and three flavonol aglycones, quercetin (6), kaempferol 3,7-dimethyl ether (7), and kaempferol 3,7,4'-trimethyl ether (8), were also isolated and are reported here for the first time in this species. The structures of compounds 1 and 2 were established on the basis of their LC-MS and one- and two-dimensional (1D)- and (2D)-NMR spectroscopic analyses, combined with acid methanolysis and silylation of sugar moieties for GC-MS. Evaluation of the antioxidant activity, conducted in the 96-well plate format, showed that the flavonoids isolated possess strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and moderate oxygen radical absorption capacity.

Searching for new antioxidants used in pharmaceuticals, cosmetics or agrochemicals have increased today. Many phenolic compounds have been reported as promising for this goal. Melastomataceae is rich in these compounds. Consequently, in this research the antioxidant power for Meriania nobilis and M. hernandoi ( Melastomataceae) was compared. Both species were extracted in acetone 70%. The latest was liquid-liquid partitioned in ethyl acetate (Mn or Mh 2.1), n-butanol (Mn or Mh 2.2) and aqueous fractions (Mn or Mh 2.3). Antioxidant activity was measured by DPPH free radical scavenging method (FRS50, mg.L-1), ferric reducing antioxidant power assay (FRAP, mg FeS04.7H20 (100 g)-1ES) and total phenolic content (TPC, mg AG g-1ES) by Folin-Ciocalteu. The present study revealed that Mh 2.1 and Mh 2.2 from M. hernandoi have a strong antioxidant power FRS50 = 5.71±0.085, FRAP = 53±1.5 and TPC = 224±7.1 and FRS50 = 4.22±0.001, FRAP = 65 mg±1.5, TPC = 240 ±8.6 respectively, as compared with positive control, quercetin DPPH FRS50 = 4.20±0.410, FRAP = 61±1.3. M. nobilis exhibited poor antioxidant power FRS50 = 286±1.5, FRAP = 2.01±0.079 and TPC = 26±1.5. This paper showed M. hernandoi as good source of antioxidant compounds with potential usage as cosmetic, pharmaceutical or agrochemical ingredients

Two dibenzylbutane lignans, dihydroguairetic acid and austrobailigan-6 were isolated as mixture of their diastereoisomers from the bark ethanolic extract of Dugandiodendron argyrotrichum (Magnoliaceae), a colombian endangered species. Characterization was achieved by 1H and 13C NMR, DEPT, COSY, HMQC, HMBC and GCMS analysis. The diastereoisomer separation by GC and the diastereospecific fragmentation patterns in negative chemical ionization mass spectrometry (NCI-MS) spotlights on an interesting tool for stereochemical research.

Determining the antioxidant activity and the total phenolic content are routine procedures in most natural product laboratories; however, when dealing with large number of samples, it is necessary to employ methods that allow a quick, easy and economical screening. The aim of this study is to determine the antioxidant activity and the total phenolic content of plant species as criteria for the selection of promising species. To reach this aim, we used twenty species from Yotoco National Protected Forest in Valle del Cauca, Colombia. The species Clidemia tococoidea and Miconia aeruginosa, showed the highest total phenolic content together with the best antioxidant activity in terms of DPPH radical scavenging activity. The excellent correlation (R2=0.9610) shown between these parameters, demonstrated the utility of the process used as a method for primary screening and selection of promising species for phytochemical analysis at a preparative scale for this two assays.

The Melastomataceae family, the seventh largest flowering plants, has been studied in several fronts of natural product chemistry, including terpenoids, simple phenolics, flavonoids, quinones, lignans and their glycosides, as well as a vast range of tannins or polyphenols. This review concerns the phenolic and polyphenolic metabolites described in the literature for several genera of this family, the mode of isolation and purification, and the structure elucidation of these new natural products that has been achieved by extensive spectral analyses, including ESI-MS, ¹H-, (13)C-NMR spectra and two-dimensional experiments, COSY, TOCSY, J-resolved, NOESY, HMQC, DEPT, and HMBC, as well as chemical and enzymatic degradations and the chemotaxonomic meaning. Finally, a general biogenetic pathway map for ellagitannins is proposed on the bases of the most plausible free radical C-O oxidative coupling.

The genus Pilea Lindley is the largest among the Urticaceae family. The large size and little commercial interest of this genus make difficult its taxonomy, with few revisions since Weddell.Very few revisions have been reported about the Colombian species since 1939, when Killip made a contribution to the genus for the northern Andes (Ecuador, Peru, Colombia, and Venezuela). To contribute to the knowledge of the Pilea genus in Colombia, field trips were made in the department of Valle del Cauca and ten herbarium samples were analyzed using gas chromatography-mass spectral profiles analysis; which allowed us to identify 33 compounds type monoterpene, sesquiterpene,diterpene, free fatty acids or their methyl, ethyl esters or amides, and triterpenes. It was concluded that Triterpenes were the best chemotaxonomical discriminants for the ten herbarium samples as ten species.

A novel and selective method to quantify lipid peroxidation in Pisum Sativum by measuring one of its secondary products, malondialdehyde, by its reaction with N-methyl-2-phenylindole was validated in this study. It has been reported that indirect effect of heavy metals in plant macromolecules via reactive oxygen species (ROS) production is more toxic and fast than its direct effect. The OH• is produced by metal-catalized Fenton reaction, as a consequence, metal presence in soils may potentiate lipid peroxidation. Enzymes such as cyclooxygenase and lipoxygenase may initiate lipid peroxidation too, therefore, either ROS scavenging or LOX or COX inhibition is convenient routes to diminish lipid peroxidation occurrence. Two way anova was performed to determine if interaction between time and treatment result in a significant difference between MDA levels in twelve plants. Bonferoni test revealed that treatment was not consistent with time. The day that resulted in significant difference of MDA was the eighth day. MDA to perform the reaction was extracted from groups of twelve 8-day plants by sonication in hydrochlorhydric acid. A calibration curve using 1,1,3,3, tetramethoxypropane as MDA standard, HCl 1 N in methanol, acetonitrile-methanol (3:1) as solvent was performed. Its linear range was 0,0078 μM to 1 μM with a 99,8% correlation. Sensibility of the method was enhanced by variation of time and temperature. Repeatability reported as variation coefficient yielded 7,8% for the standard curve and 19,6% for the samples, being these latter representative of combined biological and chemical variability. A natural flavonoid rich fraction extracted from Siparuna gigantotepala and a synthetic pyrimidine-type compound were evaluated as potential lipid peroxidation inhibitors. Flavonoid rich fraction inhibits the reaction by scavenging radicals while pyrimidine-type compound inhibits LOX and COX enzyme-catalized lipid peroxidation. Both potential inhibitors showed lipid peroxidation inhibition as evidenced by returning MDA concentration in stressed plants to that in control plants.

Al final de la novena versión del “Congreso Colombiano de Fitoquímica” organizada por el Grupo Polifenoles UTP-CENIVAM en la Universidad Tecnológica de Pereira (Mayo, 2007), surgió la necesidad de una publicación seriada especializada en el área de productos naturales. La gran acogida que tuvo el evento, se manifestó con una asistencia cercana a las 300 personas de casi todo el país, entre investigadores de larga trayectoria y jóvenes de postgrado y pregrado; además de una nutrida participación con más de 150 artículos publicados en un número especial de la “Revista Scientia et Technica (Vol. XIII, No. 33)”. La versión anterior, la octava, realizada en la Universidad de Sucre, en Sincelejo, también fue publicada en la “Revista Actualidades Biológicas (2005, Vol. 27, suplemento 1) con 26 artículos y 43 resúmenes. Las siete versiones anteriores habían tenido, también, una asistencia similar y los trabajos se publicaron en libros de resúmenes.