1,720,979 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
Sesquiterpene lactones from Centaurea zuccariniana and their antimicrobial activity
No full textTwenty-nine compounds were isolated from the aerial parts of the Greek plant C. zuccariniana DC. The structures of the isolated compounds were established by means of NMR- (1H,1H-COSY, 1H,13C-HSQC, HMBC, NOESY, and ROESY) and mass-spectral analyses. These compounds comprise 13 sesquiterpene lactones, 14 flavonoids, two lignans, and one simple lactone. Among the isolated sesquiterpene lactones, three are new, namely one heliangolide, (1E,4Z)-15-hydroxy-8α-O-(4′- acetoxy-3′-hydroxy-2′-methylidenebutanoyl)-6βH, 7αH-germacra-1,4,11(13)-trien-6,12-olide; and two eudesmanolides, 8α-(4′,5′-diacetoxyangeloyl)sonchucarpolide and one unusual eudesmanolide with an oxygenated bridge linking C(1) and C(4), named zuccarinin. The main sesquiterpene lactones were malacitenolide, cnicin, and 4′-O-acetylcnicin. These results are in agreement with those obtained from the previously studied Greek Centaurea sp. belonging to the section Acrolophus (Cass.) DC.; this finding could be of chemotaxonomic significance for the genus Centaurea. The in vitro antimicrobial activities of the isolated new sesquiterpene lactones were against eight bacteria and eight fungal species. A 96-well microbioassay procedure for fast and easy evaluation of antibacterial and antifungal activities was applied to compare these compounds with commercial antibiotic and fungicide standards, and with previously isolated analogous sesquiterpene lactones tested by the same bioassay. All of the compounds tested showed moderate antibacterial, but significant antifungal activities; the present results corroborate with previous data, indicating that these types of compounds exhibit low or moderate antibacterial, but potent antifungal activities. The unusual eudesmanolide zuccarinin proved to be the most potent among the present tested sesquiterpene lactones, as well as among all previously tested eudesmanolides isolated from Greek Centaurea sp. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich
Antimicrobial properties of Quercus ilex L. Proanthocyanidin dimers and simple phenolics: Evaluation of their synergistic activity with conventional antimicrobials and prediction of their pharmacokinetic profile
No full textThe antibacterial and antifungal activities of an ample number of phenolic compounds isolated from Quercus ilex leaves, belonging to the classes of flavonoids, proanthocyanidins, and phenolic acids, are discussed. The isolation of A type proanthocyanidin, (+)-epigallocatechin-(2β→O→7, 4β→8)-(+)-catechin (1) is reported for the first time. Its structure was established by means of highfield NMR (correlation spectroscopy, heteronuclear single quantum correlation, heteronuclear multiple bond correlation, and rotating frame Overhauser effect spectroscopy) and MS spectral analyses, while its absolute configuration was determined by circular dichroism measurements. The isolated compounds were tested for their antimicrobial effects against eight human bacterial species and 14 fungal species. In a second step, the most potent compounds were tested in combination with the conventional fungicides, bifonazole and ketoconazole, to evaluate possible synergistic effects. Results showed that proanthocyanidins 3 and 4 when combined with bifonazole and ketoconazole increase the activity of both of these conventional fungicides. Moreover, the pharmacokinetic profile of the isolated compounds was investigated using computational methods. © 2011 American Chemical Society
Sesquiterpene lactones from anthémis melanolepis and their antibacterial and cytotoxic activities. prediction of their pharmacokinetic profile
No full textNine sesquiterpene lactones, anthemin A (1), lα- hydroxydeacetylirinol-4α,5β-epoxide (2), anthemin C (3), tatridin A (4), l-epi-tatridin B (5), anthemin B (6), 6-deacetyl-β-cyclopyrethrosin (7), elegalactone A (8), and lβ,4a,6a-trihydroxyeudesm-1 l-en-8a-12-olide (9), were isolated from the aerial parts of A. melanolepis in addition to eight known flavonoids and three phenolic acids. Compounds 1, 3, and 6 are new natural products. The structures of the compounds were deduced by spectroscopic methods. The in vitro antimicrobial potential of the isolated sesquiterpene lactones against four Gram-positive and five Gram-negative bacteria and one fungus was evaluated using the microdilution method, and their in vitro cytotoxic activity was determined against a panel of human tumor cell lines. Furthermore, the pharmacokinetic profile of the sesquiterpene lactones was investigated using computational methods. © 2010 American Chemical Society and American Society of Pharmacognosy
Polar Constituents from the Aerial Parts of Origanum vulgare L. Ssp. hirtum Growing Wild in Greece
No full textFrom the polar extracts of Origanum vulgare L. ssp. hirtum 19 compounds have been isolated. The structures and relative stereochemistry have been elucidated by spectroscopic analysis and determined as apigenin, luteolin, chrysoeriol, diosmetin, quercetin, eriodictyol, cosmoside, vicenin-2, caffeic acid, p-menth-3-ene-1,2-diol 1-O-â-glucopyranoside, thymoquinol 2-O-â-glucopyranoside, thymoquinol 5-O-ß-glucopyranoside, thymoquinol 2,5-O-ß-diglucopyranoside, 12-hydroxyjasmonic acid, 12-hydroxyjasmonic acid 12-O-â-glucopyranoside, lithospermic acid B, rosmarinic acid, 10-epi-lithospermic acid, and epi-lithospermic acid B. The three latter products display unusual stereochemistry of the 3,4-hydroxyphenyllactic acid unit(s), which to the authors’ best knowledge has never been reported before in similar compounds. Moreover, lithospermic acid B (and its stereoisomers), p-menth-3-ene-1,2-diol 1-O-ß-glucopyranoside, 12-hydroxyjasmonic acid, and 12-hydroxyjasmonic acid 12-O-ß-glucopyranoside were isolated for the first time from Origanum species
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
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