1,720,985 research outputs found
Antioxidant activity of the volatile oils and methanol extracts from olive stems
No full textThis study was designed to examine the chemical composition and antioxidant activities of the volatile oils and methanol extracts of Olea europaea L. (cvs) chemlali and neb jmel stems. GC and GC–MS analyses of the volatile oils resulted in the identification of 38 and 35 compounds, representing 91.1 and 87.4 % of the volatile oils. Phenylethyl alcohol was found in the volatile oil of each cultivar, which was also the major volatile component of cv. chemlali and cv. neb jmel stems. Besides benzyl alcohol, methyl salicylate and 3-ethenylpyridine were the main volatile compounds of cv. chemlali, while nonanal, 3-ethenylpyridine and benzyl alcohol of cv. neb jmel stems were also the main constituents. Significant differences were also found in total tannin contents among two cultivars, representing 8.10 mg CEQ/g DW in cv. chemlali and 20.47 mg CEQ/g DW in cv. neb jmel. The highest contents of total phenols and o-diphenols were observed in stems extracts of cv. neb jmel (78.26, and 9.56 mg/100 g, respectively). The HPLC profiles for methanol extracts from stems of cv. chemlali and cv. neb jmel showed that oleuropein, vanillic acid and gallic acid were the predominant free phenolic compounds. Antioxidant activities of the volatile oils and the methanolic extract from stems parts
were evaluated by DPPH and ABTS? radical-scavenging activity assays. In all tests, methanolic extracts obtained from stems parts showed better antioxidant activity than volatile oils. Principal components analysis of the phenolics content and antioxidant activities showed discrimination between methanol extracts of the two cultivar
Composition and antioxidant and antimicrobial activity of the volatile oils from Olea europaea L. fruit and stem
No full textThe aims of this study was to analyze the chemical composition of fruits and stem volatile oils of Olea europaea L. cv. Chemchali and to test the efficacy of volatile oils against four pathogenic bacteria and four phytopathogen strains and their antioxidant activity. The GC-MS analysis revealed 38 compounds representing 88.5 and 73.6% of the total oils containing 3-ethenylpyridine (12.5%), (E)-2-decenal (11.4%) and 2-ethylbenzaldehyde (7.7%) in fruit and nonanal (9.9%), (E)-2-decenal (9.6%) and benzyl alcohol (9.00%) in stem as major components, respectively. The antibacterial and antifungal activities of stem volatile oils were relatively good. Therefore, the stem of Olea europaea L. demonstrated higher activities against tested fungi and bacteria than the fruit. The DPPH and ABTS-radical-scavenging activities of the oils showed that the lowest EC50 value was detected in volatile oil from fruit
Effect of the growing area and cultivaron phenolic content and volatiles compounds of related products of selected Tunisian olive varieties
No full textThis chapter reports a comparative study based on the volatile compds., polyphenols, orthodiphenols and flavonoides content from the northern Tunisian cultivars; chemlali and neb jmel and from the southern Tunisian cultivar; chemchali. There were differences between the leaves, fruits and stems from the cultivars when grown in the different environments. Volatiles oils were also influenced by the pedoclimatic conditions and the organ; hence, the leaves and stems of the southern varieties seem to be richer in total alcs. and total C6 alcs. than the northern variety. The sesquiterpene hydrocarbons, present in all the volatiles oils studied was more abundant in leaves volatile oil from the northern varieties (14.7% and 15.9% for chemlali and neb jmel, resp.) than in the southern variety. Results presented suggest the assumption that accumulation of polyhenols is most active in the fruits of the southern cultivar and generally more active in the leaves and stems of the northern cultivars than southern cultivars. In general, the genetic (varietal) and organs studied may be used to discriminate and to characterize the location conditions
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
Improvement of Chemlali olive oil oxidative stability by blending with Chétoui and Rekhami cultivars
No full textIn order to improve the quality of Chemlali olive oil, characterised by a very low stability (2.09 h), blending with two different monovarietal oils in various proportions: Chetoui and Rekhami (known by their higher stability 7.79 and 13.99 h, respectively) was carried out. Results showed that blended oils had an improved oil composition compared to that of Chemlali. In fact, the highest percentage of Chetoui and Rekhami olive oils (90% of blending) can reduce the acidity up to 68.79% and 79.61%, respectively. At 50% blending, oleic acid increased from 53% to 59.54%, while palmitic acid decreased from 20.97% to 14.89% with Chetoui olive oil. At the lowest percentage (10–20%), chlorophylls in Chemlali olive oil underwent significant increase (from 0.18 to 0.47 and 0.65 mg kg)1, respectively). The amount of carotenoids was higher when Chemlali was blended by 20–40% with Che ́toui olive oil (from 2.23 to 4.13 and 4.33 mg kg)1). Blending can be used in industrial applications to provide oils with improved composition related to stability, nutrition and functionality and endowed with the characteristics requested by consumers’ preference
Chemical composition and biological activities of volatile fractions from three Tunisian cultivars of olive leaves
No full textThe chemical composition, antibacterial, and antifungal activities of the volatile fractions from fresh and dried leaves of three Olea europaea L. cultivars from Tunisia (Neb jemel, Chemchali and Chemlali) have been studied. The volatile components were obtained via hydrodistillation and analyzed by GC–MS. The major constituents were (E)-3-hexenol, 3-ethenylpyridine, (E)-β-damascenone and phenylethyl alcohol, but their percentages varied according to the treatment of the leaves. Antioxidant activities were determined applying DPPH and ABTS+ radical-scavenging assays. In general, antioxidant activity of the volatile fraction obtained from fresh leaves was superior to that obtained from dried leaves. The antibacterial and antifungal activities of the volatile fractions from fresh and dried leaves were evaluated against four bacterial and four fungal strains. The volatile fractions showed significant antibacterial and antifungal effects. However, some differences were observed in the response for several microorganisms, because of the variability of the composition. This work gives further knowledge for extensive development of this medicinal plan
Contribution of irrigation and cultivars to volatile profile and sensory attributes of selected virgin olive oils produced in Tunisia.
No full textNowadays, a significant increase in intensively and irrigated managed olive orchards has occurred in Tunisia in the hope to increase the olive production. Aromatic profile with sensory analysis were considered in virgin olive oils from Arbequina, Coratina and Koroneiki cultivars grown intensively under three irrigation treatments (T1, T2 and T3 equivalent to 50%, 75% and 100% ETc.). Results showed that the aromatic quality depends first on the irrigation level applied and second on the cultivar. From sensory analysis, hay-like and greasy were the principal off-flavour detected. As the amount of supplied water increased, volatiles showed different behaviours depending on cultivar and the most important changes occurred in the release of the three alcohols ((E)-2-penten-1-ol, 1-hexanol, (E)-2-hexen-1-ol and phenylethyl alcohol) and hexanal. The most effective by irrigation regimes in separating cultivars were (E)-2-hexenal, (Z)-2-penten-1-ol, (E)-2-hexen-1-ol, fruity, bitter and pungent sensory descriptors. In conclusion, the data obtained herein proved the heavy influence of the cultivar in comparison with irrigation regimes
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