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Gino Funaioli. I Cesari di Suetonio
No full textGino Funaioli. I Cesari di Suetonio. In: Supplément critique au Bulletin de l'Association Guillaume Budé, n°1,1929. pp. 168-169
Gino Funaioli. I Cesari di Suetonio
No full textGino Funaioli. I Cesari di Suetonio. In: Supplément critique au Bulletin de l'Association Guillaume Budé, n°1,1929. pp. 168-169
INITIAL CHARACTERIZATION OF STEM BARK EXTRACTS FROM PHYLLANTHUS MUELLERIANUS AS SOURCE OF NEW NATURAL ENTITIES WITH ANTI-CHOLINESTERASE PROPERTIES
No full textThe plant kingdom is an endless source of chemically diverse bioactive compounds, which are used in traditional folk medicine for the treatment of a wide array of diseases. A previous investigation on the bioactive phytocomponents present in the methanol extract of Phyllanthus muellerianus (PMME) demonstrated an interesting activity against C. sporogenes (MIC= 100 μg/ml) and S. pyogenes (MIC= 300 μg/ml) [1], which supported the traditional use of the extract by local populations in Cameroon.
Looking for activity beyond the claimed traditional use [2], PMME was evaluated on human cholinesterase enzymes, namely acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) as selected targets for Alzheimer’s disease (AD) treatment. Indeed AChE inhibitors derived from natural products (galanthamine and rivastigmine) are currently licensed to alleviate cognitive symptoms in dementia. Due to the limited available pharmacological treatments for AD, extensive research has been directed towards the identification of other AChE inhibitors, arising from the plant kingdom. A rational basis for our investigation on the bark extracts of Phyllanthus muellerianus is related to a study carried out in 2007 by Joshi e Parle, in which the antiamnesic potential for Phyllanthus amarus in mice was demonstrated [3].
Anticholinesterase activity was in vitro evaluated by Ellman’s assay [4] using recombinant human AChE and BuChE from human serum.
Due to the interesting activity found for the de-fatted PMME (% inhibition at 100 g mL-1 on hAChE = 52.6 ± 0.6, on hBuChE = 70.1 ± 3.1%, n=4), PMME was fractionated by flash chromatography affording six fractions (PMF1-6); PMF1, PMF2 and PMF4 significantly inhibited human cholinesterases, thus they were further purified by a RP-18 solid phase extraction.
The bio-guided fractionation allowed the identification of three active phytocomponents, with different selectivities against the two ChEs. Two out of the three bioactives have been isolated so far: compound A from PMF1 and compound B from PMF4, both alkaloids. Compound A showed to be a hBuChE selective inhibitor (IC50 = 44.8 ± 3.0 g mL-1 and IC50 = 382 ± 15 g mL-1, for hBuChE and hAChE, respectively) while compound B showed comparable inhibitory potencies against both enzymes (IC50 = 5.45 ± 0.20 g mL-1 and IC50 = 12.6 ± 0.4 g mL-1, for hAChE and BuChE, respectively).
Compared to the commercially available AD drug galanthamine, compound B is one order of magnitude less active on hAChE (galanthamine IC50 = 0.6 g mL-1), representing, however, a potential new natural scaffold to undergo towards optimization.
The chemical structure of the two isolated alkaloids is under investigation by 13C and 1H-NMR. Moreover, the isolation of compound C in suitable amount for the evaluation of the biological profile and its structural elucidation has being carried out.
References
[1] G. Brusotti, I. Cesari, G. Frassa, P. Grisoli, C. Dacarro, G. Caccialanza, J. Ethnopharmacol., 2011, 35, 797–800.
[2] R. Brisson, Etudes pygmées, SELAF n 376, Ed Peeters, 1999, Paris.
[3] H. Joshi and M. Parle, African Journal of Biomedical. Research., 2007, 10, 165–173.
[4] G.L. Ellman, K.D. Courtney, V. Jr. Andres, R.M. Feather-Stone, Biochem. Pharmacol., 1961, 7, 88-9
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
Chemical Composition Of The Essential Oil From Stem Bark Of Phyllantus Muellerianus (Kuntze) Excell (Euphorbiaceae) by GC-MS
No full textDispelling 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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