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Activity of extracts from three tropical plants towards fungi pathogenic to tomato (Solanum lycopersicum)
Get PDFAntifungal properties were assessed of water and ethanol extracts from the pan-tropical plants Oxalis barrelieri L., Stachytarpheta cayennensis L., and Euphorbia hirta L. against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani Sorauer, and Rhizoctonia solani Kuhn. The plant extracts inhibited fungal growth in vitro at 1.25-20 mg mL-1, and the degrees of inhibition increased in a dose-dependent manner. Ethanol extracts from the plants inhibited fungal growth by 80-100%, while water extracts showed less antifungal activity, with maximum growth inhibition of 62%. Growth inhibition from ethanol extracts was two- to three-fold greater than for water extracts at equivalent concentrations. Antifungal activity of the extracts varied with their content and composition of phenolics, flavonoids, tannins, and alkaloids. In greenhouse experiments, spraying tomato plants (Solanum lycopersicum L.) with ethanol extract from E. hirta at 2.5 mg mL-1 did not cause phytotoxicity, and increased plant size, when compared to untreated plants. Spraying E. hirta ethanol extract on tomato plants infected by R. solani reduced disease severity up to 80%, when compared to non-sprayed plants. These results demonstrate potential of leaf extracts from E. hirta, O. barrelieri, and S. cayennensis as biofungicides for the control of R. solani, A. solani, and F. oxysporum, which are among the most important causal agents of tomato diseases
Phenolic compounds profile of water and ethanol extracts of Euphorbia hirta L. leaves showing antioxidant and antifungal properties
Get PDFThe bioactive chemical constituents of water and ethanol extracts of Euphorbia hirta L. leaves have been identified and quantified using an un-targeted mass spectrometric approach. The study allowed the tentative identification of 123 individual phenolic compounds and 18 non-phenolic phytochemicals, most of them described in Euphorbia hirta L. leaves for the first time. Gallotannins, hydroxybenzoic and hydroxycinnamic acids were the most abundant phenolic classes in Euphorbia hirta L. leaves, representing together the 71.5% (26.3%, 25.2% and 20%, respectively) of the total amount of identified phenolics. The main phenolic compounds detected were tri-O-galloyl-glucose isomers, feruloyl-coniferin, tetra-O-galloyl-glucose isomers, di-O-galloyl-glucose isomers, ethyl-gallic acid, protocatechuic acid-O-pentoside-O-hexoside, 5-O-caffeoyl-quinic acid trans isomer and digalloyl-quinic acid. Feruloyl-coniferin was found to be approximately six times more concentrated in the ethanol extract with respect to the water extract. The ethanol extract exhibited higher ABTS (1338.3 ± 85.3 and 802.3 ± 91.0 μmol ascorbic acid equivalent/gram of dry extract, respectively) and superoxide anion (2014.6 ± 78.6 and 1528.0 ± 111.7 μmol ascorbic acid equivalent/gram of dry extract, respectively) scavenging abilities than the water extract. Additionally, the ethanol extract also showed a remarkable anti-fungal effect against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani and Rhizoctonia solani. This study provides new information about Euphorbia hirta L., offering reasons to promote this plant species as rich source of phenolics and an excellent source of antifungal molecules that might have a prospective use in controlling fungal diseases of vegetable crops
ANTIFUNGAL ACTIVITY OF AQUEOUS AND ETHANOL EXTRACTS OF TROPICAL PLANTS AGAINST TOMATO FUNGAL PATHOGENES.
No full textSeveral plant extracts may have a strong antifungal activity
that can be exploited in the management of fungal diseases as an
alternative to synthetic fungicides, the abuse of which may have
consequences on the environment and health. Ethanol extracts
(EE) and water extracts (WE) of three tropical plants, Stachytarpheta
cayennensis (Verbenaceae), Oxalis barrelieri (Oxalidaceae) and
Euphorbia hirta (Euphorbiaceae) were obtained and screened for
their antifungal activity against three major phytopathogenic fungi
of tomato: Fusarium sp., Alternaria sp. and Colletotrichum sp. The
phytopathogenic fungi used across the experiments were isolated in
Cameroon on severely affected tomatoes and their molecular identification
and characterization is ongoing. The antifungal activity was
checked in vitro on different media supplemented with different
concentrations of the extracts. O. barrelieri EE, at the concentration
of 25 mg/ml, inhibited the mycelium growth of Fusarium sp. by
26.8% and remarkably modified its morphology. WE and EE of the
same O. barrelieri inhibited the mycelium growth of Colletotrichum sp. by 43.7% and 50.3% respectively, but showed no inhibition on
Alternaria sp. The phytochemical analysis of these plant extracts
revealed that EE of S. cayennensis was the richest in polyphenols
and flavonoids. EE from O. barrelieri was particularly rich in alkaloids.
The inhibitory effects on the phytopathogenic fungi were possibly
related to the amount of polyphenols and alkaloids obtained
through the extraction. Field experiments are being conducted on
tomato to confirm the action of such extracts in vivo. These findings
may contribute to develop new biofungicides to protect tomato
from some fungal pathogens
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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