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Medicinal plant polyphenols in vitro activity on glycation and oxidative stress related to vascular diseases
No full textNatural phenolic compounds and flavonoids have received attention for their biological effects, such as antioxidant and antiglycative activities.
The polyphenols studied in this research are characteristic phytoconstituents of several medicinal plants widely used in traditional medicine such as: baicalein (from Scutellaria baicalensis G.), eupatorin (Eupatorium semiserratum DC.), galangin (Alpinia officinarum L.), magnolol (Magnolia officinalis L.), myricetin (Myrica rubra S. Z.), oleuropein (Olea europaea L.) and silybin (Silybum marianum L.)
Effects of plant-derived polyphenols on glycation and oxidative stress related to vascular diseases
Full text linkThere is a large amount of evidence indicating that oxidative stress and glycation play a crucial role in aging as well as in neurodegenerative and cardiovascular diseases. Oxidative stress is linked with reactive oxygen species (ROS), whose harmful effects can lead to several pathological conditions like vascular alterations, diabetes complications and inflammation. Moreover, ROS and oxidative stress can directly contribute to glycation reactions with the formation of reactive α-oxoaldehydes and advanced glycation end-products (AGEs). The glycation process is characterized by non-enzymatic reactions between aldehyde or keto groups of sugars and free amino-residues of proteins, which lead to the formation of AGEs. Glycation and AGEs cause the irreversible modification of the proteins structure and the consequent loss of their functionality, causing detrimental effect in vasculature. Thus, it can be reasonable that compounds which counteract the effect of oxidative stress and glycation may assume an important role in the prevention of vascular damage. Natural phenolic compounds and flavonoids have received attention for their biological effects, such as antioxidant and antiglycative activities. Despite the health claims of polyphenols, it is known that their bioavailability can vary dramatically depending on many factors. The effects of the polyphenols, and of their in vivo circulating metabolites, will ultimately depend on the extent to which they associate with cells, either by interactions at the membrane or more importantly by their cellular uptake. Therefore, in order to assess the potential activity of natural polyphenols, it is primarily important to evaluate the intestinal permeability and bioavailability. In this research, human colorectal carcinoma cells (HT-29) were used as experimental model of intestinal cells, to evaluate the polyphenols ability to cross the cellular membrane and permeate into the cell. The polyphenols studied in this research are characteristic phytoconstituents of several medicinal plants widely used in traditional medicine such as: baicalein (from Scutellaria baicalensis G.), eupatorin (Eupatorium semiserratum DC.), galangin (Alpinia officinarum L.), magnolol (Magnolia officinalis L.), myricetin (Myrica rubra S. Z.), oleuropein (Olea europaea L.), and silybin (Silybum marianum L.).
The aims of the PhD project were firstly to evaluate the HT-29 intestinal cells permeability of natural compounds, and secondly, to investigate the in vitro antiglycation activity of polyphenols and their activity against endothelial cellular damage related to oxidation and glycation, using HUVEC cells as experimental model for endothelium function. The results showed that the ability of polyphenols to cross the HT-29 cell membrane depends on many factors, including molecular size and hydrophilic properties of each compound. The flavonoids baicalein, eupatorin and galangin were able to cross the HT-29 cell membranes and undergo biotransformation process; conversely, oleuropein seemed to not been taken up in the HT-29 cells. The results of AGEs determination showed that most of the polyphenols, at the higher concentration, displayed antiglycative activity in all experimental conditions, and that baicalein, eupatorin and galangin showed the highest activity in counteract the AGEs formation.
In the experimental model involving HUVEC, the aim was to evaluate the potential role of several compounds related to hyperglycemia and glycation, such as glycated albumin, glyoxal and glucose at high concentration, in inducing cytotoxicity and oxidative stress. Moreover, the antioxidant activity of the selected natural compounds against the oxidative stress induced by those factors was assessed using the DCFH-DA assay. The results from ROS detection assay showed that the glycation products known as glycated albumin and glyoxal were not able to directly induce oxidative stress in HUVEC in the assay conditions, whereas glucose at high concentration displayed an effect of oxidative stress induction. Therefore, high glucose was used as oxidative stressor in the polyphenols evaluation assay. Baicalein, eupatorin and galangin were selected as natural compounds with a potential antioxidant activity, and their activity on ROS formation in HUVEC induced by high glucose was evaluated. The highest antioxidant activity was seen after the pre-treatment with the polyphenols at the concentration of 5 μM.
All together, the results obtained motivate further researches on the activities of polyphenols against oxidative and glycative damages in order to understand their potential role in the prevention of vascular diseases
Plant-derived polyphenols and intestinal HT-29 cells: understanding the cellular uptake.
No full textThe polyphenols have aroused great scientific interest, since their beneficial effects are attributed to their antioxidant activity: the phenolic compounds can act as metal chelators, antimicrobial agents, radical scavengers, and might also trigger changes in cells and in the signaling pathways, as by preventing the LDL oxidation, platelet aggregation, and ROS generation. The health effects of polyphenols depend also on their bioavailability, which can vary greatly because of different factors, as the degree of hydroxylation, the molecular conformation, etc. A critical point in the debate on health effects of polyphenols is indeed their bioavailability, therefore we used the human colorectal carcinoma cells (HT-29), which are a reference model of intestinal cells, to evaluate the polyphenols ability to pass through the cellular membrane and permeate into the cell.
The polyphenols studied in this research are from medicinal plants widely used in traditional medicine: baicalein (from Scutellaria baicalensis G.), eupatorin (Eupatorium semiserratum DC.), galangin (Alpinia officinarum L.), magnolol (Magnolia officinalis L.), myricetin (Myrica rubra S. Z.), oleuropein (Olea europaea L.) and silybin (Silybum marianum L.)
In vitro pharmacological studies on the bioavailability of flavonoid compounds and on AGEs formation
No full textFree radicals and reactive oxygen species (ROS) are responsible for the oxidative stress which causes damage to cellular membranes, proteins, and DNA, affecting many human tissues. Thus, oxidative stress is involved in the genesis of several pathological conditions like vascular alterations, diabetes complications, inflammatory diseases and so on. Furthermore, advanced glycation end-products (AGEs) are well-known contributors to the pathophysiology of these complications, because glycated proteins in vivo may in turn promote the formation of free radicals; hence, glycation and oxidative stress are intimately interrelated. A role in prevention of chronic diseases is given to antioxidant compounds, among these, natural phenolic compounds and flavonoids have received attention for their biological effects, such as antioxidant and antiglycative activities. Despite the health claims of flavonoids, it is known that the bioavailability of flavonoids is generally low and can vary dramatically among different flavonoid classes as well as individual compounds in a particular class. In fact, the effects of these polyphenols and their in vivo circulating forms will ultimately depend on the extent to which they associate with cells, either by interactions at the membrane or more importantly by their cellular uptake.
The aim of this research was to evaluate the antiglycative activity of several flavonoid compounds and to investigate their uptake by intestinal cells, in order to have a preview on their in vivo properties. The flavonoids studied were baicalein, eupatorin, galangin, myricetin, and silibinin, which are well known plant-derived polyphenols widely used in traditional medicine. Advanced glycation end-products (AGEs) were determined using bovine serum albumin (BSA) as protein substrate and glucose, ribose or glyoxal as glicative agents. Glucose and ribose are sugars found in vivo in physiological conditions, while glyoxal is a highly reactive dialdehyde, a metabolite produced during the autoxidation of glucose. To assess the cellular uptake of flavonoids, we used as experimental model the human colon carcinoma (HT29) cells which were incubated for three hours with the flavonoid compounds (1-5 μM). The flavonoid content of the cells was analyzed by high performance liquid chromatography (HPLC) equipped with a UV diode array detector. The results showed that flavonoid compounds possess antiglycative activity in the BSA-sugar assay in comparison with aminoguanidine as positive control. Further, the data on the cellular flavonoids uptake showed that these compounds are partially taken up by HT29 cells. Others studies are in progress to determine the cellular uptake and antiglycative activity of the flavonoid compounds
Antioxidant and antifungal activities of the Cameroonian medicinal plant Annona muricata
No full textAnnona muricata L. (Annonaceae), commonly known as Soursop, Guanàbana or Graviola, is a small,
upright evergreen tree of 5-6 m, with large, glossy, dark green leaves, which produces an edible fruit
well known for its health properties. Although it is native of America, Annona muricata become
established in many tropical countries of the world. The plant has been used in traditional medicine
for many diseases, especially against infections and cancer. Effectively, it has been used in African
herbal medicine systems for its sedative and antispasmodic properties, and also as hypotensive,
insecticide, vermifuge, and for coughs, fevers, pain and skin diseases. Several chemical compounds
have been isolated from the plant Annona muricata, and phytochemical investigations revealed the
presence of alkaloids, tannins, coumarins, flavonoids, terpenoids. Among these compounds,
researchers evidenced isoquinoline alkaloid annonaines, and acetogenins as the main active
principles from Annona muricata.
The aim of this research was to investigate the antioxidant capacity and antifungal activity in vitro of
ethanolic extracts obtained from leaf, stem and root of Annona muricata. The antioxidant capacity has
been evaluated using assays based on different mechanisms: the Oxygen Radical Absorbance
Capacity (ORAC) assay, based on HAT reaction, and DPPH radical scavenging capacity assay, based
on SET reaction. We also determined the Total Flavonoid Content (TFC) and the Total Phenolic
Content (TPC) for each extract. Furthermore, the antifungal activity was studied by evaluated the
MIC (minimum inhibitory concentration) and MFC (minimum fungicidal concentration) in different
strains of Candida
In vitro radical scavenging activity of essential oils from Brazilian medicinal plants: Croton zehntneri, Pterodon emarginatus and Schinopsis brasiliensis
No full textthe objective of this study was the phytochemical characterization of the essential oils of three traditionally used species, known as Croton zehntneri Pax et Hoffm., Pterodon emarginatus Vogel and Schinopsis brasiliensis Engl. The antioxidant activities were also determined by the use of 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay1,2 and oxygen radical absorbance capacity (ORAC) assay3,4. The essential oil of Pterodon emarginatus was extracted from the seeds, while the Schinopsis brasiliensis oil from the leaves and finally, the Croton zehntneri oils were obtained from leaves or bark. The qualitative and quantitative characterization of essential oils was carried out by gas chromatography/mass spectrometry (GC/MS); the constituents were identified by comparison of their mass spectra with those from NIST Mass Spectral Database
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
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