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Prunus persica by-products: A source of minerals, phenols and volatile compounds
Full text linkLarge amounts of peach (Prunus persica) leaves and stems are by-products deriving from peach tree cultivation and canned industries. This work aimed to evaluate mineral nutrients, phenolic and volatile profile and anti- oxidant activities from the by-products of five peach cultivars (Early Maycrest, Sweet Cap, O’Henry, Flordastar and Rubirich). Minerals showed significant variations with respect to peach by-product. N showed higher contents in peach leaves among macronutrients, while Mn showed higher contents among micronutrients. Stems had high levels of Ca and traces of micronutrient levels. The HPLC-DAD phenols analysis showed twelve compounds identified (neochlorogenic and chlorogenic acids, catechin and epicatechin, gallic, caffeic, syringic, ferulic and coumaric acids, quercetin-3-rutinoside, quercetin-3-galactoside, cyanidin-3-glucoside, cyanidin-3-galactoside). Flavonols showed the highest values (quercetin-3-galactoside with 70.79–232.16 mg 100g-1 DW, quercetin-3-rutinoside with 63.88–206.37 mg 100g-1 DW), while the least content was observed for anthocyanins. Cultivar had a sig- nificantly (P < 0.05) impact on phenolic compounds. Comparing by-products, stems showed higher levels of phenols. The GC-MS volatile compounds analysis revealed 43 compounds in different percentages and occur- rences, depending on the cultivar and the by-product. Benzaldehyde was detected as the major volatile leaf component (70–95%), whereas myrcene (18–21%) and terpinolene (18–26%) were found to be the most im- portant compounds in stems. Methanolic extracts of mature leaves were characterized by lower antioxidant capacity. Finally, peach by-products could represent a natural source of minerals, volatiles and phenolic com- pounds with high antioxidant activities having a great potential use in food products as natural flavouring agents and as nutraceutical supplements and pharmaceutical and cosmetic molecules
Phytochemical Compounds from the Crop Byproducts of Tunisian Globe Artichoke Cultivars
No full textThe phytochemical composition in two Tunisian globe artichoke cultivars (bracts, leaves, and floral stems) was evaluated in the plant byproducts. The results indicated that the bracts contain the highest levels of total phenols, o-diphenols, and flavonoids, whereas tannins seem to be more abundant in the leaves. Bracts from the 'Violet d'Hyères' cultivar possessed more total phenols (160.8 mg/g DW), flavonoids (64.9 mg/g DW), and anthocyanins (15.3 μg/g DW) than the 'Blanc d'Oran' bracts (134.5 mg/g DW, 51.2 mg/g DW, and 8.3 μg/g DW, resp.). Sixty-four volatile compounds were identified in the headspace of globe artichoke material, particularly in the bracts. The volatile profile showed that sesquiterpene hydrocarbons and non-terpene derivatives were the main volatiles emitted by the bracts in both cultivars. These results suggest that globe artichoke byproducts might represent a potential source of natural compounds, which could be used as nutraceuticals or as ingredients in the design of functional foods
Changes in biochemical compounds in flesh and peel from Prunus persica fruits grown in Tunisia during two maturation stages
Full text linkPlants can synthesize tens to hundreds of thousands of primary and secondary metabolites with diverse biological properties and functions. Fatty acids (FA), phenolic compounds (PC) and volatile compounds (VC) of flesh and peel from three Prunus persica cultivars were evaluated at the Regional Centre of Agricultural Research - Experimental Farm (Sidi Bouzid, Tunisia) during two maturation stages. Palmitic, oleic and linoleic acids are the most abundant FA in Prunus persica cultivars. A genetic effect on FA composition was observed throughout the two sampling periods. Peel was rich in oleic acid with the highest content (31.3% on total FA) in 'O'Henry' cultivar at the commercial ripening date; flesh was rich in linoleic acid with the highest content (44.7% on total FA) in 'Sweet Cap' cultivar at the full ripening date. The monounsaturated/polyunsaturated fatty acids ratios were higher in the commercial ripe than in the full ripe fruits. The analysis of the composition of the VC led to the characterization of 98 different compounds, showing a very high variability among the cultivars. The full ripe fruit (peel and flesh) exhibited the highest total number of terpenoids. Commercial ripe peels were richest in the percentage of hydrocarbons. Comparing cultivars, 'Sweet Cap' cultivar showed the lowest contents of alcohols in peel and flesh of full ripe fruit but highest in peel of commercial ripe fruit, and lowest content of aldehydes in peel and flesh of commercial ripe fruit but highest in peel of ripe ones and the highest ones of lactones. Among PC, the highest contents were observed for o-diphenols and the values showed varietal influence. Total phenols contents decreased during ripening process (p < 0.05) in both peel and flesh tissues, except found for 'Sweet Cap' cultivar. In conclusion, to achieve better FA composition and greater VC and PC production of the peach fruit, P. persica cultivars should be harvested at the commercial ripening date
Carotenoids, Phenolic Profile, Mineral Content and Antioxidant Properties in Flesh and Peel of Prunus persica Fruits during Two Maturation Stages
Full text linkCarotenoids and phenolic profile, antioxidant activity as well as concentrations of selected macronutrients (K, N, Mg, Ca and Na) and micronutrients (Zn, Cu and Mn) in flesh and peel of peach fruit were recorded at two harvest dates. Predominant mineral was potassium, followed by calcium, magnesium and sodium. The concentration of most micronutrients was greater in the peel than in the flesh especially in early season. The concentration of most elements in flesh and peel decreased during fruit maturation. Total carotenoids content varied with respect to the cultivar. β-cryptoxanthin and β-carotene were the major carotenoids in both tissues and flesh contain the lowest amounts. Neochlorogenic acid, chlorogenic acid, catechin, epicatechin, gallic acid, rutin, quercetin-3-O-galactoside, cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, were detected in both peel and flesh, with chlorogenic acid and catechin being the predominant components. Peel extracts showed markedly higher antioxidant activities, when estimated by ABTS or DPPH assays, than the flesh counterparts, consistent with the observed higher phenolic content. Overall, total phenolics levels increased at full ripening stage in both peel and flesh. The results found herein provide important data on carotenoids, phenolic and macro- and micronutrient changes during fruit growth, and emphases peach fruit as a potential functional food
Content of fatty acids and phenolics in Coratina olive oil from Tunisia: influence of irrigation and ripening.
No full textThe quality indices and chemical composition of Coratina olive oil produced in the northern region of Tunisia were evaluated, to determine the effect of three different irrigation regimes of the trees on the olive oils. The olives were sampled at two different stages of maturity, the oils were extracted, and standard methods were used to analyze the composition and quality of the oils. The fatty-acid contents and quality parameters were only slightly affected by the irrigation regime. The contents of palmitic, oleic, and linoleic acids were above 12, 72, and 8%, respectively, for the second harvest, regardless of the irrigation level of the olive trees. Parameters such as the α-tocopherol content and the phenolic profile were found to be significantly affected by the harvesting time; however, inconsistent changes were observed for the irrigation regimes, especially for the oil of the second harvest. It was shown that the irrigation conditions of the olive trees as well as the harvesting time of the fruits gave rise to a diverse range of olive oils in Tunisia
Biochemical characterization and antioxidant activities of the edible part of globe artichoke cultivars grown in Tunisia
Full text linkA renewed interest was observed recently in the globe artichoke as a promising source of polyphenols, a heterogeneous class of secondary metabolites characterized by various well-documented healthy properties. However, only few studies characterized Tunisian cultivars. Therefore, the present study aimed at evaluating the chemical parameters [fatty acids (FA), volatiles and phenolic derivatives content] in the edible part, the receptacle, of two globe artichoke cultivars (‘Violet d’Hyéres’ and ‘Blanc d’Oran’), including their antioxidant activities. FA profiles of the receptacles showed that the most abundant acids were linoleic and palmitic ones. Forty-one volatile compounds, accounting for 97.6 - 96.3% of the receptacle aroma emission were identified. Sesquiterpenes hydrocarbons represented the main chemical class, in particular β-selinene followed by β-caryophyllene reached the highest levels in ‘Violet d’Hyéres’ (48.7% and 14.5%, respectively). Total phenols and tannins (P ≤ 0.05), o-diphenols and flavonoids (P ≤ 0.01) were significantly higher in the receptacles of ‘Violet d’Hyéres’ cultivar (73.0, 17.2, 15.4 and 12.2 mg 100 g−1 of fresh weight, respectively). The antioxidant activity was notably phenolic derivatives content-dependent where the higher values were observed in ‘Violet d’Hyéres’ cultivar. Results suggested that globe artichoke receptacles could represent a good source of health-promoting polyphenols with high antioxidant activity and this fact could encourage their consumption. Further investigations are needed to evaluate the variation of the considered compounds in other Tunisian cultivars
Cinétique enzymatique
No full text<p>Ce cours de <em><strong>cinétique enzymatique</strong></em> est adressé aux étudiants en médecine </p>
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
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