1,720,959 research outputs found
Cardenolides from Pergularia tomentosa display cytotoxic activity resulting from their potent inhibition of Na+/K+-ATPase.
No full textTwo new cardenolide glycosides (1 and 2), along with six known cardenolide glycosides (3-8), have been isolated from the roots of Pergularia tomentosa. In order to investigate their potential anticancer activity, these compounds were tested in an in vitro growth inhibitory assay (a MTT colorimetric assay), including six different human cancer cell lines, and for their ability to inhibit Na(+)/K(+)-ATPase activity, in addition to the morphologic changes induced in human cancer cell lines (using computer-assisted phase-contrast microscopy). The data revealed that these cardenolides displayed marked cytotoxic activity. The results obtained suggest that structural characteristics of the cardenolides studied, with the A/B rings of the steroidal skeleton trans fused and containing a single sugar in a unique "dioxanoid" attachment, confer on them specific cytotoxic properties that are distinct from those displayed by classic cardenolides such as digoxin.Journal Articleinfo:eu-repo/semantics/publishe
Phenolic Compounds from the Fruits of Medemia argun, a Food and Medicinal Plant of Ancient Egypt
No full textMedemia argun is a mysterious and little known monotypic fan palm from the Nubian Desert Oases of southern Egypt and northern Sudan. Its fruits have been found in the tombs from the 5th Dynasty (ca. 2500 BC) to Roman times (6-7th century AD), including the celebrated tomb of Tutankhamun. In ancient Egypt, the fruits of this palm were widely distributed and were highly valued, as confirmed by their frequent occurrence in offerings in the tombs. In order to elucidate the chemical composition of the phenolic fraction, phytochemical investigation of the BuOH extract of fruits was carried out to afford eight compounds (1-8), among which was the new 2,4-dihydroxy-6-methylacetophenone 2-0-β-D-glucopyranoside (1). With the aim to investigate if the high shelf life of M argun fruits could be related to the occurrence of antioxidant principles that were able to prevent oxidative reactions, the evaluation was carried out of the in vitro antioxidant activity by Trolox equivalent antioxidant capacity (TEAC) assay of the extract and isolated compounds
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Flavone C-glycosides from Vaccaria pyramidata: Structure elucidation by spectroscopy and theoretical calculations
No full textThe flavone C-glycosides namely apigenin-7-O-β-D-glucopyranosyl-8-C-β-D-glucopyranoside (1) and apigenin-8-C-α-L-rhamnopyranosyl-(1→2)-O-β-D-glucopyranoside (2), along with p-methoxycinnamic acid (3), vaccaroside A (4), vaccaroside D (5), vaccaroside E (6) and abscisic acid glucose ester (7) were isolated from the methanol extract of the aerial parts of Vaccaria pyramidata. Structure elucidation of compounds 1-7 was accomplished by the extensive use of 1D- and 2D NMR experiments along with HR-ESI-MS. The structures of 1-2 have been confirmed by theoretical study of the 1H, 13C chemical shifts and UV data. In addition, Ionization Potential (IP) and Bond Dissociation Enthalpy (BDE) were used to evaluate the theoretical antioxidant activity of compounds 1 and 2. TD-DFT method (time-dependent density functional) was used to calculate the electronic absorption spectra of compounds 1 and 2 from optimized structures in methanol and the orbitals involved in the electronic transition were elucidated
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