1,720,984 research outputs found
Alnus glutinosa (L.) Gaertn. and Alnus cordata (Loisel) Duby as new sources of safe cosmetic and pharmacological anti-melanogenic agents
No full textThe genus Alnus (Betulaceae) comprises many species with a long history in traditional medicines. The crude extracts and isolated compounds from Alnus species exhibit a wide spectrum of in vitro and in vivo pharmacological activities (1). Phytochemical investigations revealed the presence of diarylheptanoids, a class of natural products typically found in Alnus genus with two aryl groups joined by a heptane chain in the main skeleton that have drawn attention due to their multiple biological properties and their therapeutic potential (2). A previous study reported that oregonin and other structurally analogous diarylheptanoids isolated from the bark of A. hirsuta showed inhibitory effects on melanogenesis in B16 melanoma cells.(3). Nowadays the discovery of new whitening agents from natural sources is increasing, due to the weak effectiveness and unwanted side effects of currently available compounds.
In this context, the aim of this study was to evaluate the skin whitening capabilities of crude extracts (80% aqueous MeOH) obtained from the fresh bark of Alnus glutinosa (L.) Gaertn. and Alnus cordata (Loisel) Duby, an endemic species in the Mediterranean areas (4). As tyrosinase is the rate-limiting enzyme in melanin biosynthesis, the inhibitory effects of A. glutinosa and A. cordata extracts (AGE and ACE, respectively) on mushroom tyrosinase activity were preliminary evaluated. In addition, the anti-melanogenic ability of AGE and ACE was further investigated on the pigmentation of early stage zebrafish at 72 hours post fertilization (hpf) to find new skin whitening agents without cytotoxic concerns.
Results of the enzymatic assay showed that ACE was capable to inhibit dose dependently L-DOPA oxidation catalyzed by tyrosinase (IC50 = 77.44 ± 0.54 μg/mL) as compared to the reference inhibitor kojic acid (2.24 ± 0.18 μg/mL). Unlike, AGE exhibited a lower anti-tyrosinase activity (100 μg/mL reached 28% of inhibition while higher doses showed pro-oxidative effects). Moreover, the zebrafish in vivo assay revealed that ACE (50 μg/mL) has equivalent inhibitory effects on the pigmentation (76.57%) to that of phenylthiourea (PTU, 30 μg/mL), used as the reference inhibitor (77.80%), as compared to control, while they did not affect the embryos development and survival. Conversely, the depigmenting effects of AGE were about 10 fold less than ACE (45.28% at 500 μg/mL). A mild anti-melanogenic activity was also evidenced for the diarylheptanoid oregonin (10% of inhibition at 20 μg/mL).
A preliminary phytochemical screening evidenced that ACE and AGE have a high phenolic content (399.27 ± 14.30 and 534.17 ± 20.60 mg GAE/g of extract, respectively). However, despite AGE showed the highest phenolic content, the quali-quantitative RP-HPLC-DAD analysis highlighted as it is predominantly composed by oregonin (418.45 μg/mg of AGE vs 1.23 μg/mg of ACE) that exhibited a mild anti-melanogenic activity both in vitro and in vivo assays. Further phytochemical investigations are still in progress to identify the bioactive compounds of ACE as to be considered a potential candidate for the treatment of skin disorders due to its bleaching properties and favorable safety profiles
Antioxidant activities of extracts from various portions of giant orchid, Himantoglossum robertianum (Loisel.) P. Delforge
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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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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