1,720,972 research outputs found
Physiological and oxidative stress responses of lettuce to cleomside A: a thiohydroximate, as a new allelochemical from Cleome arabica L.
Full text linkThe inclination toward natural products have led the onset for the discovery of new bioactive metabolites that could be targeted for specific therapeutic or agronomic applications. This study aimed to isolate bioactive compounds from Cleome arabica L., and subsequently determine the unexplored mechanism of action of the newly identified compounds on Lactuca sativa L. Chemical investigation of the ethyl acetate fraction of methanolic silique extract of C. arabica afforded seven secondary metabolites belonging to different classes such as flavonoids, triterpene, and a new thiohydroximate derivative, named cleomside A. Among phytotoxic assays, the growth of lettuce was totally inhibited by cleomside A compared to the other identified compounds. This effect was associated with the increased levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide indicating disruption of membrane integrity and induction of oxidative stress. Activities of the antioxidant enzymes SOD, CAT, and APX were also elevated, thereby demonstrating the enhanced generation of reactive oxygen species upon identified allelochemical exposure. Thus, the changes caused by cleomside A described herein can contribute to better understanding the allelochemical actions of thiohydroximate and the potential use of these substances in the production of natural herbicides compared to the other identified flavonoids and triterpene
Olive Wastes as a High-Potential by-Product: Variability of Their Phenolic Profiles, Antioxidant and Phytotoxic Properties
No full textThe global world olive oil industry produces large amounts of wastes and wastewaters. However, the disposal of these polluting by-products is a significant environmental problem owing to their high polyphenolic compounds. In order to learn possible ways of exploiting this waste, we investigated the phytochemical profiles, the phytotoxicity and the antioxidant activities of olive wastes (leaves, mill wastewater (OMWW) and mill solid waste (OMSW)). Leaf extracts exhibited the highest phytotoxic and antioxidant effects, which are mainly due to its phenolic content. The chromatographic profiles depicted eleven phenolic compounds belonging to secoiridoids, phenyl alcohols, phenolic acids, phenylethanoid glycoside, and flavonoids. Hydroxytyrosol and oleuropein were the main components in leaf methanol and OMWW extracts, respectively, exhibiting an amount of 13.05 and 4.39 mg/g DW. These results will help to demonstrate the possibility of utilizing olive wastes, particularly the leaf, as an inexpensive natural product, in food and agricultural applications. Graphic Abstract: [Figure not available: see fulltext.]
Impact of foliar potassium fertilization on biochemical composition and antioxidant activity of fig (Ficus carica L.)
No full textThe metabolic processes involved in fig production are influenced by macro- and micronutrients supply to the
trees during the growing season. Potassium is an essential plant nutrient that influences growth and fruit quality.
In this study, the effect of foliar potassium sulphate (K2SO4) application on biochemical composition and antioxidant
activity of fig was assessed in cv. Bouhouli, a commonly cultivated cultivar in Djebba (Northwest of
Tunisia). Foliar potassium sulphate supply at 2% on Bouhouli trees were applied twice during the fruit growth.
Results exhibited that potassium fertilization induces a significant change in total phenolic, flavonoid contents
and radical scavenging activity in total fruit and achenes compared to the control. A strong correlation was
observed between antioxidant activity and different phenolic compounds. The total fruit and achenes methanol
extracts possess, respectively, the highest values of polyphenol by 29.3 and 25.1 mg GAE/g DW compared to the
control. Similarly, the flavonoids content was increased in methanol extracts, respectively, by 36 and 48%. HPLC
analyses revealed the influence of potassium on concentrations of phenolic compounds in fig sprayed with
K2SO4. Among the polyphenols, the chlorogenic acid, cyanidin 3-rutinoside and cyanidin 3,5-diglucoside contents
increased from 0.87 to 1.70 mg/g DW under potassium spray, whereas those compounds were not detected
in fig achenes. The present study provides clear evidence that potassium sulphate can be used to manipulate total
phenolic concentrations in fig with strong antioxidant potential that could be benefits to human health. Thus,
potassium sulphate application at 2% could improve nutritional and qualitative attributes of fig
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
Allelopathic potential and phenolic allelochemicals discrepancies in Ficus carica L. cultivars
No full textThe phytotoxic effect of some tree species could act as an ecological filter through chemical production that influences plant growth of other species. Despite this widespread interest, few studies have investigated the allelopathic effect of some Moraceae species, while this mechanism has not been studied in Ficus carica. To address this research, we attempted to identify the allelopathic mechanisms of thirteen local preserved fig cultivars on the germination and seedling growth of common weeds and standard target species. The results stated that all fig extracts displayed significant phytotoxic impact, and the degree of inhibition was appeared to be dependent on the cultivars and target species. In general, leaf extracts were more toxic and significantly influenced the seedling elongations, as compared to twig extracts. It was clearly marked that the germination and growth of weed species were totally affected by leaf aqueous and methanol extracts of cultivars Kahli and Bouhouli, respectively, at 40 g/L and 6 g/L. The phytochemical analysis through high performance liquid chromatography detected similar profile among cultivars but with a significant disparity in phenolic composition. Among the identified compounds, rutin is the major flavonoid compound recorded in cv. Zidi and was highly accumulated in leaf rather than in twig. It was obvious that the different fig cultivars or even their tissues can be characterized and clustered in three groups based on their allelopathic potential and phenolic compounds
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
Sartans: What they are for, how they degrade, where they are found and how they transform
No full textSartans are chemical compounds with antagonistic action towards the AT1 receptors of angiotensin II, a multifunctional peptide with vasoconstrictor action and one of the main peptides responsible for regulating blood pressure. Losartan (progenitor of the group), valsartan, irbesartan, candesartan, eprosartan, telmisartan and a few other compounds belong to this class. The use of sartans, introduced in the mid-90s of the last century, has quickly spread mainly due to the alleged reduction in the incidence of certain adverse effects of varying severity (cough, angioedema) associated with the intake of ACE inhibitors. Their very strong commercial success together with their low metabolic degradation and high environmental persistence has consecrated them as emerging pollutants in just 20 years. This review presents a complete picture of sartans in relation to their chemical structure, chemical-physical properties and by-products in aqueous solutions as well as under oxidative and photodegradative conditions, their environmental presence and knowledge known to date and their fate in wastewater treatment plants
New Acylated Oleanane and Lupane Triterpenes from Gymnema sylvestre
No full textPhytochemical investigation of the aerial parts of Gymnema sylvestre led to the isolation of two
known oleanane-type triterpenes, 1 and 3, five new acylated derivatives, 2, 4, and 5 – 7, and a new lupanetype
triterpene, 8. The structures and relative configurations of these compounds were elucidated by
spectroscopic analyses, including 1D- and 2D-NMR spectroscopy and mass spectrometry, and by the
comparison of their NMR data with those of related compounds
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