1,720,965 research outputs found
LC-DAD-ESI/MS identification of active natural products from four plants species
No full textIn our work on the project NUTRASNACK (E.C. F.P.6 contract No FOOD-CT-2005-023044) composition of the extract from basil (Ocimium basilicum), dandelion (Taraxacum officinale), soybean (Glycine max), mint (Mentha piperica) was evaluated using hyphenated technique liquid chromatography combined with mass spectrometry LC-DAD-ESI/MSn.
Applying this technique major consituents were preliminary identified or confirmed if appropriate standards were available.
For basil, five phenolic constituents were identified: flavonoid (unknown), phenolic acid (unknown), chicoric acid and rosmarinic acid; minor peaks corresponding to quercetin glycosides were present.
In dandelion extract cis- and tras-caftaric acids, two unknown phenolic acid, chlorogenic acid and chicoric acid were identified.
Soybean extract contained 15 individual isoflavones with characteristic UV spectra. Based on their MSn their structures were confirmed.
The mint phenolics contained rosmarinic acid, number of isoflavones and flavonols. Due to the fact that the structure of several compounds could not be confirmed because of their complexity and the lack of appropriate standards their preparative separation has been performed to produce reference substances
Extraction and purification of active natural products from four plants species
No full textThe project NUTRASNACK (E.C. F.P.6 contract No FOOD-CT-2005-023044) has the main objective to produce by in vitro cultures secondary metabolites with health benefits, which can be used for fortification of some food products. On the of the key partner is ENERVIT®, a well-known firm in the development of nutrition programs to enhance the performances of athletes and sportsmen. For the purpose of the project a number of plant species have been selected for the study of the possibility of commercial application of their secondary metabolites. This includes basil (Ocimium basilicum), dandelion (Taraxacum officinale), soybean (Glycine max), mint (Mentha piperica) and Leguminosae species (genus Trifolium).
For above species the conditions and protocols for the extraction of active principles need to be established. These protocols are aimed at the preparation of extracts for analytical purposes but also for commercial application for separation of large amounts of phytochemicals. For this purpose he extraction with different solvents and the purification of extracts by Reversed Phase C18 or Amberlite XAD4 Solid Phase Extraction.
It was shown that in case of green samples two options should be considered. For samples used for analytical purposes the 70% EtOH should be a case of choice. For commercial purposes the water extract is more reasonable. Water extracts contain all active chemicals and allow to avoid chlorophyll presence in the extract. This substantially simplified the method of purification and enrichment.
In case of soybean the EtOH extract is necessary as isoflavones are not so readily soluble in water. Further purification can be achieved by SPE
The ultra-performance liquid chromatography (UPLC) analysis of phenolics in four plant species
No full textFor the evaluation of the efficiency of in vitro systems and for standardization of commercial products the reliable fast analytical procedures are required. These are usually based on HPLC analysis. Regular HPLC separations are usually time and solvent consuming. The new achievements in analytical equipment allows to apply much faster technique UPLC for plant phytochemical analysis. The technology is quite new (developed in 2004) and in this respect there is no literature available. It was applied for separation of phenolics in the extracts of four plant species: basil (Ocimium basilicum), dandelion (Taraxacum officinale), soybean (Glycine max), mint (Mentha piperica) considered as a source of nutraceuticals researched under the project NUTRASNACK (E.C. F.P.6 contract No FOOD-CT-2005-023044).
The Acquinity Ultra Performance Liquid Chromatograph (Waters) consisting of Binary Solvent Manager, Sample Manager, PDA detector and Empower Pro 2.0 software was used. The analyses were performed on an UPLC BEH C18 column (1.7mm, 50mm ́ 2.1mm) utilizing a gradient elution profile and a mobile phase consisting of 0,1% acetic acid in water and 40% AcN. The column was maintained at 50oC and at a flow rate was kept constant at 0.35 mL/min.
The separation profiles obtained for four analysed species were of similar quality as the profiles obtained with HPLC. However, optimization of the separation conditions (water-acetonitrile gradient shape, column temperature) in UPLC allowed us to reduce separation time down to 5 min (basil, dandelion) and 6 min (mint and soybean); regular HPLC separation time was 50 min. The developed method simplified the analytical protocol and shortened the time of analysis just to few minutes. This an important achievement when big number of samples e.g. in vitro culture efficiency evaluation is necessary
”LC-DADESI/MSn identification of active natural products from four plants species.”
No full textIn our work on the project NUTRASNACK (E.C. F.P.6 contract No FOOD-CT-2005-023044) composition of the extract from basil (Ocimium basilicum), dandelion (Taraxacum officinale), soybean (Glycine max), mint (Mentha piperica) was evaluated using hyphenated technique liquid chromatography combined with mass spectrometry LC-DAD-ESI/MSn.
Applying this technique major consituents were preliminary identified or confirmed if appropriate standards were available.
For basil, five phenolic constituents were identified: flavonoid (unknown), phenolic acid (unknown), chicoric acid and rosmarinic acid; minor peaks corresponding to quercetin glycosides were present.
In dandelion extract cis- and tras-caftaric acids, two unknown phenolic acid, chlorogenic acid and chicoric acid were identified.
Soybean extract contained 15 individual isoflavones with characteristic UV spectra. Based on their MSn their structures were confirmed.
The mint phenolics contained rosmarinic acid, number of isoflavones and flavonols. Due to the fact that the structure of several compounds could not be confirmed because of their complexity and the lack of appropriate standards their preparative separation has been performed to produce reference substances
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
Design and biophysical characterization of atrazine-sensing peptides mimicking the Chlamydomonas reinhardtii plastoquinone binding niche
No full textVariations 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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