1,720,972 research outputs found
A novel sesquiterpene lactone from Centaurea pullata: Structure elucidation, antimicrobial activity, and prediction of pharmacokinetic properties
No full textA novel elemanolide with an α-methyl-γ-lactone moiety, 8α-O-(4-hydroxy-2-methylenebutanoyloxy)melitensine, in addition to four known sesquiterpene lactones also bearing the same lactone ring, melitensin, 11β,13 dihydrosalonitenolide, 8α-hydroxy-11β,13-dihydro-4-epi-sonchucarpolide, and 8α-hydroxy-11β,13-dihydro-onopordaldehyde have been isolated from the aerial parts of Centaurea pullata. The in vitro antibacterial and antifungal activities of the isolated sesquiterpene lactones were tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used. Moreover, the pharmacokinetic profile of these compounds was investigated using computational methods. © 2008 Elsevier Ltd. All rights reserved
Analgesic and antioxidant activities of Algerian Retama raetam (Forssk.) Webb & Berthel extracts
No full textPart of this work deals with the isolation and structure elucidation of the main polar secondary metabolites of the aerial parts of Retama raetam (Forssk.) Webb & Berthel, as well as the evaluation of their potential analgesic properties, while the rest deals with the antioxidant activities of the aqueous extracts of roots, stem, fruits and flowers of the plant. It was found that the isoflavones genistein 1, 6-hydroxygenistein 2, 3'-Omethylorobol 3, pratensein 4, biochanin A 8, the flavones 6-hydroxyapigenin 7 and luteolin 5, the flavonol kaempferol 6, as well as the phenolic compound p-coumaric acid 9 reduce significantly the pain at a concentration dose of 1 mg/kg. The most active compounds were 3 and 8 (86.19% and 75.23%, respectively). The obtained aqueous extracts of R. raetam were also evaluated for their antioxidant activities using two different photometric methods; the results revealed that all extracts exerted very low free radical scavenging activity compared to the well-known butylated hydroxytoluene (BHT) and lower hydrogen peroxide blocking activity than positive control gallic acid
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
Occurrence of flavonoids in Ophrys (Orchidaceae) flower parts
No full textThe flower parts (i.e. sepals, labellum, gynostemium and isolated pollinia) of four Ophrys species (Ophrys argolica, Ophrys apifera, Ophrys cornuta, and Ophrys delfinensis [O. argolica×O. cornuta]), native in Greece, were examined for the presence of polyphenolic compounds. The chemical composition was studied by chromatographic and spectroscopic techniques (UV-vis and 1D and 2D NMR), whereas the localization of the phenolic compounds was depicted by epifluorescence microscopy. The chemical composition was highly variable among the different flower parts. Pollinia and sepals contained the highest concentrations of flavonoids, while the labellum contained the lowest. Among species, O. apifera showed the highest (up to 6-fold) concentration of flavonoid compounds compared with the other three species. Microscopic observations showed that flavonoids are localized in the protoplast, especially in proximity of the nucleus. They are concentrated on cuticle and cell walls of epidermal cells and in parenchyma cells of the sepals. The pollinia contained high concentrations of flavonols which were deposited in the pollen grains. Three kaempferol (Km) glycosides, Km 3-O-β-d-glucoside, Km 3-O-β-d-rutinoside and Km 3-O-β-d-rhamnoside, were the dominant compounds in the pollinia. The above results suggest a UV-protective role for flavonoids in the flower parts of these plants. Additionally, the pollen-specific flavonols could also be related to the flavonol-depended male fertility known from other plant species. © 2008 Elsevier GmbH. All rights reserved
Minor sesquiterpene lactones from Centaurea pullata and their antimicrobial activity
No full textThe aerial parts of Centaurea pullata afforded, in addition to the previously isolated sesquiterpene lactones, 11β,13-dihydrocnicin and 11β,13-dihydro-19-desoxycnicin, three minor sesquiterpene lactones, namely, a new germacranolide, 8α-0-(4-acetoxy-5-hydroxyangeloyl)-11β,13- dihydrocnicin, and two new eudesmanolides, 8α-0-(4-hydroxy-2- methylenebutanoyloxy)-11β,13-dihydrosonchucarpolide and 8α-0-(4-hydroxy-2-methylenebutanoyloxy)-11β,13-dihydro-4-epi- sonchucarpolide. The in vitro antimicrobial activity of all isolated sesquiterpene lactones was tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used. © 2007 American Chemical Society and American Society of Pharmacognosy
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
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