1,720,968 research outputs found
Di- and Triterpenoids from Cameroonian Plants
No full textIsolation and structural elucidation of di- and triterpenoids from Cameroonian plants will be presented. In particular, we will report the isolation of a new oleanane-type triterpenoid from Combretum molle, two new clerodane diterpenoids from Dioscorea bulbifera, and two new triterpene saponins from Entada rheedii; all the plant materials were collected near Dschang (west province of Cameroon).
Combretum molle is used in African traditional medicine for the treatment of fever, abdominal pains, convulsion and worm infections.1 Dioscorea bulbifera is used by tribal people in Bangladesh for treatment of leprosy and tumours.2 Several species of Entada are used in traditional medicines for various diseases,3 but not much is known about Entada rheedii.
Details of the structural elucidation and the results of biological activity tests will be also reported.
1. Bessong P. O., Obi C. L., Igumbor E., Andreola M.-L., Litvak S., Afr. J. Biotechnol., 2004, 3, 555-559.
2. Murray R. D. H., Jorge Z., Khan N. H., Shahjahan M., Quaisuddin M., Phytochemistry, 1984, 23, 623–625.
3. Tapondjou A. L., Miyamoto T., Mirjolet J.-F., Guilbaud N., Lacaille-Dubois M.-A., J. Nat. Prod., 2005, 68, 1185-1190
Bafoudiosbulbins F and G, further clerodane diterpenoids from Dioscorea bulbifera L. var sativa and revised structure of Bafoudiosbulbin B
No full textFrom the bulbils of Dioscorea bulbifera L. var sativa, two clerodane diterpenoids, Bafoudiosbulbins F (1)
and G (2), together with five known compounds: Bafoudiosbulbins A–C, 3,5,40-trihydroxy-30-methoxybibenzyl,
and kaempferol were isolated. Their structures were established by spectroscopic techniques,
including 1H, 13C NMR, NOESY, ROESY, COSY, TOCSY, HSQC, and HMBC. The relative stereochemistry of
compounds 1 and 2 was assigned on the basis of X-ray crystallographic diffraction analysis. Furthermore,
the structure of Bafoudiosbulbin B was revised using extensive 2D NMR techniques as well as chemical
transformatio
Rheediinosides A and B, two antiproliferative and antioxidant triterpene saponins from Entada rheedii
No full textTwo triterpenoid saponins have been isolated from the seed kernels of Entada rheedii. Their structures
have been established using 1D- and 2D-NMR and mass spectrometry as 3-O-b-D-xylopyranosyl-
(1 -3)-O-a-L-arabinopyranosyl-(1 -6)-2-acetylamino-2-deoxy-b-D-glucopyranosylentagenic acid 28-
O-b-apiofuranosyl-(1-3)-b-D-xylopyranosyl-(1 -2)-b-D-glucopyranoside (Rheediinoside A, 1) and
3-O-b-D-glucopyranosyl-(1 -3)-O-[b-D-xylopyranosyl-(1-3)-a-L-arabinopyranosyl-(1 -6)]-2-acetylamino-
2-deoxy-b-D-glucopyranosylentagenic acid 28-O-b-apiofuranosyl-(1-3)-b-D-xylopyranosyl-
(1-2)-b-D-glucopyranoside (Rheediinoside B, 2). Compounds 1 and 2 were tested for their antiproliferative
activity against T98G, A431, PC3 and B16-F1 cell lines, and further for their antioxidant properties.
Moderate cytotoxic potency and antioxidant properties were found for these compounds whereas Rheediinoside
B was in all assays more active than Rheediinoside A
Clausena anisata and Dysphania ambrosioides essential oils: from ethno-medicine to modern uses as effective insecticides
No full textDysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) and Clausena anisata (Willd.) Hook. f. ex Benth. (Rutaceae) are two aromatic species traditionally used in Cameroon to repel and kill insects. The present work was carried out to substantiate this traditional use and to evaluate the possible incorporation in commercial botanical insecticides of their essential oils (EOs). The EOs were distilled from leaves of C. anisata and aerial parts of D. ambrosioides and analyzed by gas chromatography-mass spectrometry (GC-MS). The insecticidal activity of both EOs was investigated against the filariasis vector, Culex quinquefasciatus, and the housefly, Musca domestica. As possible mode of action, the inhibition of acetylcholinesterase (AChE) by the two EOs was investigated as well. The D. ambrosioides EO was characterized by the monoterpene peroxide ascaridole (61.4%) and the aromatic p-cymene (29.0%), whereas the C. anisata EO was dominated by the phenylpropanoids (E)-anethole (64.6%) and (E)-methyl isoeugenol (16.1%). The C. anisata EO proved to be very toxic to third instar larvae of C. quinquefasciatus showing LC50 of 29.3 μl/l, whereas D. ambrosioides EO was more toxic to adults of M. domestica showing a LD50 of 51.7 μg/adult. The mixture of both EOs showed a significant synergistic effect against mosquito larvae with LC50 estimated as 19.3 μl/l, whereas this phenomenon was not observed upon application to M. domestica adults (LD50 = 75.9 μg/adult). Of the two EOs, the D. ambrosioides one provided a good inhibition of AChE (IC50 = 77 μg/ml), whereas C. anisata oil was not effective. These findings provide new evidences supporting the ethno-botanical use of these two Cameroonian plants, and their possible application even in synergistic binary blends, to develop new eco-friendly, safe and effective herbal insecticides
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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