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Aedmaasika viljade antioksüdatiivsete omaduste mõjutamise võimalustest ja metoodilistest aspektidest nende määramisel
Get PDFIt is generally acknowledged that genotype, cultivation conditions and postharvest technologies might have an effect on some antioxidant compounds in strawberries, but the extent to which different measures impact total antioxidant capacity, is rarely reported.
Also, the importance of methodological aspects in strawberry anthocyanin determination and thereafter interpreting the health-beneficial value of different cultivars is often underestimated.
The aims of the thesis were:
to give better insight into weaknesses of the widely used pH differential method for strawberry anthocyanin determination and to suggest a reliable procedure in order to get true results;
to find out whether strawberries from commercial organic (OR) farms have higher antioxidant properties compared to fruits from commercial conventional (CONV) farms;
to determine the effect of fertilizer containing phosphite anion (HPO32-) and postharvest modified atmosphere on antioxidant properties of strawberries;
to identify genotypes with outstanding antioxidant properties among new strawberry cultivars bred for growing in the northern region.
As a result of using different molar absorption coefficients which have previously been used in published literature, the total anthocyanin content for individual strawberry cultivars differed more than 50%. When the pH differential spectroscopic method is used, pelargonidin-3-glycoside with the ε=15600 M-1cm-1 would enable most precise estimation of total anthocyanin content in strawberries.
Experiments with OR and CONV strawberries indicated that if fruits from only two production sites were studied, OR strawberries had higher total antioxidant capacity. If fruits from seven different OR and CONV farms were compared, a large variation in antioxidant compounds within both OR and CONV strawberries outplayed the effect of cultivation system. Thus, OR strawberries do not necessarily contain more antioxidants compared to CONV strawberries in Estonia.
Pre-planting phosphite treatment increased strawberry fruit anthocyanins by up to 20% and ascorbic acid content by up to 40%. Postharvest modified atmosphere was effective in maintaining higher total antioxidant capacity of ‘Polka’ and ‘Honeoye’ strawberries during 5-days storage.
’Marmolada’ could be distinguished by outstanding antioxidant properties.Tõnu Tõnutare doktoritöö käsitles aedmaasika viljade antioksüdatiivsete omaduste mõjutamise võimalusi ja metoodilisi aspekte nende määramisel.
Aedmaasika viljad sisaldavad tervisele kasulikke, antioksüdatiivsete omadustega bioaktiivseid ühendeid, millest olulisemad on antotsüaanid, askorbiinhape, ellagitanniinid, erinevad fenoolsed ühendid, foolhape, vitamiin E jt. Nende ühendite sisaldus sõltub paljudest erinevatest teguritest: sordiomadused, kasvatustehnoloogia, taime varustatus kasvamiseks vajalike toiteelementidega, säilitustingimused. Käesoleva ajani ei ole õnnestunud selgitada, kui palju nimetatud tegurid suudavad mõjutada maasika viljade antioksüdatiivseid omadusi. Sordiaretuses hinnatakse uute maasikasortide puhul eelkõige saagikust, haiguskindlust, viljade suurust ja maitset, erinevate sortide antioksüdatiivsetele omadustele on pööratud vähem tähelepanu. Antioksüdatiivsete omaduste määramisel on üheks probleemiks standardiseeritud meetodi puudumine ja seetõttu on tulemused vägagi erinevad.
Üheks käesolevas doktoritöös uuritud küsimuseks oli maasikate analüüsil kasutatava antotsüaanide kogusisalduse määramise spektromeetrilise meetodi puhul kasutatava molaarse absorptsiooni koefitsiendi korrektne valik. Sõltuvalt selle koefitsiendi väärtusest võivad esitatud antotsüaanide sisaldused erineda rohkem kui 50% võrra. Lisaks uuriti aedmaasika antioksüdatiivsete omaduste mõjutamise võimalusi kasvatus- ja säilitustehnoloogiliste võtete abil. Uurimistöös jõuti järeldusele, et Eestis mahetehnoloogiaga kasvatatud maasikatel ei pruugi olla kõrgemat antioksüdatiivset aktiivsust, võrreldes tavaviljeluses toodetud viljadega. Maasikataimede istutuseelne leotamine täiendväetises, mis sisaldas fosforit traditsioonilise fosfaatiooni asemel fosfitanioonina (PO33-), suurendas oluliselt nii maasika viljade antotsüaanide kui ka askorbiinhappe sisaldust. Säilitustehnoloogiatest uuriti töös passiivselt modifitseeritud atmosfääri mõju. Selgus, et madala hapniku- ja kõrge süsihappegaasiga säilituskeskkonna mõju oli sordispetsiifiline. Nimetatud säilituskeskkond tagas ‘Polka’ ja ‘Honeoye’ viljade antioksüdatiivse aktiivsuse säilimise 5-päevase säilitusperioodi jooksul. Doktoritöös hinnati ka Itaalia sordiaretusfirma Vivai Mazzoni Ltd poolt Põhja- ja Ida-Euroopa jaoks aretatud seitsme uue maasikasordi bioaktiivsete ühendite sisaldust ja antioksüdatiivset aktiivsust. Selgus, et askorbiinhappe ja antotsüaanide sisaldus erinevate sortide vahel erines üle kahe korra ja antioksüdatiivne aktiivsus kuni 40%. Kõige silmapaistvamaks sordiks osutus ‘Marmolada’, mida iseloomustasid nii suur askorbiinhappe- ja antotsüaanide sisaldus kui ka kõrge antioksüdatiivne aktiivsus
Enzymatic Antioxidant Systems
No full textSoil enzymes have been suggested as potential indicators of soil quality because of their essential role in soil biology. Soil enzyme activities also respond to agronomic practices such as fertilizers, amendments, vegetation cover, pesticides, allelochemicals and to preservation practices. Soil enzymes are derived primarily from leaving organisms such as soil fungi, bacteria, plant roots, microbial cells and plant and animal residues. They play a significant role in mediating biochemical transformations involving organic residue decomposition and nutrient cycling in soil. The presence of soil antioxidant enzymes has an important role in protecting soil components from the oxidative stress. Besides, enzymatic activity can be used as a sensitive index to reveal changes of soil quality due to land management, possible presence of allelochemicals and to monitor soil microorganism activity related to soil nutrient transformation. Because all biochemical transformations in soil are dependent on, or related to the presence of enzymes, studying soil enzyme activities provides insight into biochemical processes in soil. Furthermore, there is growing interest in the applications of soil enzymes as early indicators of soil quality change under contrasting agricultural management practices.Fil: Vattuone, Marta Amelia. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Sgariglia, Melina Araceli. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Soberon, Jose Rodolfo. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Sampietro, Diego Alejandro. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentin
Reactive Oxygen Species
No full textMolecular oxygen (O2) is essential for the survival of all aerobic organisms, because it acts as the final acceptor of mitochondrial electron chain. In this situation, O2 is reduced to H2O after the cytochrome-c oxidase reaction. Reactive oxygen species (ROS) are extremely reactive substances derived from the O2 that may be formed during the electron transfer reactions or through photon absorption by a sensitizer molecule and subsequent reaction either by energy or electron transfer reactions with O2. The ROS not only comprise free radicals such as superoxide (O2−•), hydroperoxyl (HO2•), hydroxyl (HO•), peroxyl (RO2•) and alkoxyl (RO•) radicals, but also non-radicals such as hydrogen peroxide (H2O2), singlet oxygen (1O2), and hypochlorous acid (HOCl). Radicals are unstable with variable reactivity. Figure 1 shows the typical ROS generation pathway. Several allelochemicals can generate an uncontrolled production and accumulation of ROS on target plants. This oxidative stress is often referred as part of harmful effects of these substances on target plants. Soil allelochemicals such as quinones or phenols may become semiquinone radicals that reduce the molecular oxygen to superoxide radical and then produce other ROS on soil matrix. It may be aided by catalytic metals such as aluminum or iron most abundant metals in soils. ROS and direct depolarization by some allelochemicals which cause cellular disruption and ultimately the cell death, can initiate the lipid peroxidation of plant root membranes. Soil allelochemicals also act as inhibitory agents of antioxidizing enzymes, such as superoxide dismutase and catalase, thus leaving the plant vulnerable to ROS mediated oxidative damage. ROS production by plant roots indicates the signal of plant defence mechanism upon microbial attack. ROS accumulates in plant cells in response to pathogen infections (causing damage to cells or finally the cell death). On the other hand, soil derived ROS e.g. H2O2, may contribute to the structural reinforcement of plant cell walls and coordinate the activation of defense genes and phytoalexin production. Many events cause ROS generation and allelochemicals production in soils, thus, soil microbiological, physicochemical and mineralogical studies often includes the ROS assessment, in soil matrix or plant roots. This chapter provides useful and sensitive tests to assess the ROS content in plant-soil system.Fil: Soberon, Jose Rodolfo. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Sgariglia, Melina Araceli. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Sampietro, Diego Alejandro. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Vattuone, Marta Amelia. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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