• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 78
  • 44
  • 6
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 154
  • 154
  • 45
  • 45
  • 24
  • 19
  • 16
  • 16
  • 15
  • 13
  • 12
  • 11
  • 11
  • 11
  • 10
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Weight losses of Green tea and Rooibos tea in an aquatic environment : The importance of leaching when estimating decomposition rates / Viktförluster av Grönt te och Rooibos te i vattenmiljö : Vikten av urlakning vid estimering av nedbrytningshastigheter

Edwartz, Johannes January 2018 (has links)
Leaching is one of the major processes occurring when organic litter is decomposed and is often completed within a few days when litter enters aquatic environments. It is important that leaching is addressed when studying microbial and invertebrate decomposition rates in order to avoid overestimations. The traditional litter bag method that has been used to measure decomposition rates in both terrestrial and aquatic environments has in recent years been challenged by the new and widely adopted tea bag index (TBI). Both methods, however, fail to bring a standardized methodology for separating and recognizing weight losses of litter due to leaching and biotic decomposition. Through a field experiment in two streams with different water discharge, this study has focused on exploring the leaching phase and post-leaching phase of the tea products used in TBI. The results unveiled that 20% of rooibos tea’s and 44% of green tea’s initial weight was lost to leaching within three days (72 hours) of the experiment. After the 72nd hour, both teas remained in a stabilized phase until the end of the experiment (120 hours). Water discharge had no significant effect on neither of the tea-weights during or after the leaching phase. This study recommends that weight loss through the leaching phase are taken into account in future studies and advocate the development of an updated TBI protocol where leaching losses are recognized. If not, overestimations of active decomposition rates will be made and may result in compromised conclusions. / Urlakning är en av de viktigaste processerna som uppstår vid nedbrytning av organiskt material och är ofta slutfört inom några dagar när materialet befinner sig i vattenmiljöer. Det är viktigt att den urlakade massan beräknas när studier fokuserade på nedbrytningshastigeter av mikrober och evertebrater genomförs, detta för att undvika en överestimering av den biotiska aktiviteten. Den traditionella metoden, där torkade växtdelar i påsar, har använts för att mäta nedbrytningshastigheter i både mark- och vattenmiljöer har under de senaste åren utmanats av det nya och allmänt accepterade tepåse-indexet (TBI). Båda metoderna misslyckas dock med att implementera en standardiserad metodik för att separera och uppskatta materialets viktförluster genom urlakning och biotisk nedbrytning. Genom ett fältexperiment i två vattendrag med olika vattenföring har denna studie fokuserat på att undersöka urlakningsfasen och den stabiliserade perioden efter urlakningen hos teprodukterna som används i TBI. Resultaten avslöjade att 20% av rooibos tes och 44% av grönt tes ursprungliga vikt förloras genom urlakning inom tre dagar (72 timmar) av experimentet. Efter den 72:a timmen förblev båda teerna i en stabiliserad fas till slutet av experimentet (120 timmar). Vattenflöde hade ingen signifikant effekt på någon av tetypernas vikter, varken för perioden under eller efter urlakningsfasen. Denna studie rekommenderar att viktminskning genom urlakningsfasen beaktas i framtida studier och förespråkar utvecklingen av ett uppdaterat TBI-protokoll för att inkludera urlakningens påverkan. Om inte, kommer överskattningar av aktiva nedbrytningshastigheter att göras och kan leda till äventyrade slutsatser.
142

Mucins in the alimentary canal : their structure and interactions with polyphenols

Davies, Heather January 2014 (has links)
The polymeric gel-forming mucins provide the structural framework of saliva and the mucus barriers that cover the mucosal surfaces of the alimentary canal. Dietary compounds may influence the barrier properties of these protective layers. The effects of green tea polyphenols, which have many health benefits but have low bioavailability and contribute to the astringency of green tea, on the structural properties of the mucins in the alimentary canal are investigated here. Using well characterised, highly purified salivary mucins MUC5B and MUC7, and porcine gastric mucins, the effects of the green tea polyphenol epigallocatechin-3-gallate (EGCG) on mucins were studied here. Using rate-zonal centrifugation coupled to agarose gel electrophoresis, atomic force microscopy and particle tracking microrheology, EGCG, at concentrations found in a cup of green tea, caused increased aggregation of MUC5B in human whole saliva, and increased aggregation and viscosity of purified MUC5B. It was revealed using recombinant proteins of the N- and C-terminal regions of MUC5B that EGCG had these effects by aggregating the terminal globular protein domains of MUC5B. In contrast, MUC5B trypsin-resistant high molecular weight glycopeptides were not aggregated by EGCG, demonstrating that the oligosaccharide-rich, highly-glycosylated regions of mucins are not involved in the EGCG-induced aggregation of mucins. EGCG also caused the majority of MUC7 in human whole saliva to aggregate, and purified MUC7 also showed substantial aggregation in the presence of EGCG.Porcine gastric mucins were also used in order to model human gastric mucins. First, the identity of the porcine gastric mucins was explored using tandem mass spectrometry and immunohistochemistry. This revealed that Muc5ac was expressed by the surface epithelium and was the prominent mucin in porcine gastric mucus. Muc6 was expressed by gastric submucosal glands, but was not a major component of the secreted mucus barrier. Porcine Muc5ac and Muc6 were shown to be aggregated by EGCG. These data demonstrate that mucins from both saliva and the stomach are substantially altered by EGCG. This may contribute to the astringency and low bioavailability of EGCG. In contrast, the green tea polyphenol epicatechin (EC) did not cause aggregation of salivary mucins or porcine gastric mucins, suggesting that the galloyl ring of EGCG (which is absent in EC) is important for its aggregation of mucins, and that EC has different mechanisms of astringency. The structure of the mucins in the alimentary canal was studied using Raman spectroscopy, Raman optical activity (ROA) and Tip-enhanced Raman spectroscopy (TERS). The secondary structure of the oligosaccharide-rich regions of mucins was shown to be largely disordered, with some contribution of poly-proline II helix. The N- and C-terminal regions of MUC5B were largely β-sheet in structure, with some disordered structure also present in the C-terminal region. Raman spectroscopy could reliably distinguish between MUC5B glycoforms, demonstrating the sensitivity of this technique to mucin glycosylation and secondary structure. The first TERS spectra along the length of a MUC5B chain are reported, and suggest that patterns may exist in the glycosylation of MUC5B. Therefore, Raman spectroscopies are novel tools that shed new light on mucin structure and in future may be useful for studying the changes to mucin structure during interactions, such as those with polyphenols.
143

Effects of a blend of green tea and curcuma extract supplementation on lipopolysaccharide-induced inflammation in horses and ponies

Starzonek, Janine 23 November 2020 (has links)
Einleitung: Verschiedene Erkrankungen gehen bei Pferden mit einer erhöhten Entzündungsbereitschaft einher. Das entzündliche Geschehen kann dabei in engem Zusammenhang mit dem Auftreten von Stress des endoplasmatischen Retikulums (ER) stehen. Im Zuge der Immunantwort entsteht eine Signalkaskade, die über Entzündungsmarker quantifiziert werden kann. Bei der Expression verschiedener Entzündungsmediatoren rückt insbesondere die Leber in den Fokus. Die anti-inflammatorische und ER-Stress-modifizierende Wirkung von oralen Polyphenolen aus einem Grüntee-Kurkuma-Extrakt (GKE) wurde bereits in anderen Tierspezies, wie z.B. Wiederkäuern oder Schweinen nachgewiesen. Ziel der Studie: Das Ziel der vorliegenden Studie war die Überprüfung der Effekte einer GKE-Supplementierung auf eine Lipopolysaccharid (LPS)-induzierte Entzündung bei Pferden und Ponys. Die Hypothese war, dass die Supplementierung des GKE zu einer Reduktion der entzündlichen Reaktion und des Zellstresses bei Pferden und Ponys führt. Tiere, Material und Methoden: In einer randomisierten, placebo-kontrollierten Studie wurden fünf gesunde adulte Warmblutpferde (Angaben in Mittelwert ± Standardabweichung, Alter 19 ± 5 Jahre; Körpermasse (KM) 589 ± 81 kg) und sechs gesunde adulte Shetlandponys (Angaben in Mittelwert ± Standardabweichung, Alter 9 ± 3 Jahre; KM 126 ± 8 kg) einbezogen. Die tägliche Basisration bestand aus Heu (2 kg/100 kg KM). Im Cross-over erhielten die Tiere für 21 Tage 10 g eines GKE (20% Polyphenolgehalt) nach Angaben des Herstellers, oder alternativ ein Placebo (Kalziumcarbonat) zusammen mit 1 kg (Pferde) oder 0,2 kg (Ponys) eines kommerziellen Ergänzungsfuttermittels für Pferde. Nach der 21-tägigen Supplementierungsphase wurde bei allen Tieren zur Induktion eines moderaten, generalisierten Entzündungsgeschehens LPS (10 ng/kg KM) intravenös appliziert. 24 Stunden vor und 12 Stunden nach der LPS-Challenge wurden Blutproben und Lebergewebe entnommen. Die Entnahme des Lebergewebes erfolgte minimalinvasiv unter Ultraschallkontrolle. Während der anschließenden 3-monatigen Wash-out Phase erhielten alle Tiere ausschließlich Heu zur freien Aufnahme. Hiernach fand im Cross-over Verfahren ein Wechsel der Fütterungsgruppen statt. Eine erneute LPS-Challenge und die anschließende Probennahme wurden nach den oben genannten Kriterien durchgeführt. In allen Blutproben wurden die Parameter Serum Amyloid A (SAA), Haptoglobin (Hp) und Retinol-bindendes Protein 4 (RBP4) gemessen. Mittels RT-qPCR wurden in allen Leberbioptaten die mRNA-Level ausgewählter Entzündungsmarker bestimmt (Hp, TNF-α, IL-1β, IL-6, CD68, FGF21, NF-kB, ATF4). Zusätzlich erfolgte eine histologische Untersuchung auf entzündliche Reaktionen im Gewebe. Die Daten, mit Ausnahme der immunhistochemischen Auswertungen, wurden unter Verwendung der kommerziellen Software Statistica® statistisch ausgewertet. Die Daten wurden mittels des Shapiro-Wilks-Testes auf Normalverteilung überprüft. Da die Daten nicht normalverteilt waren, wurde der Wilcoxon-Test für nicht-parametrische Daten angewendet. Das Signifikanzniveau lag bei p < 0,05. Die Darstellung der Daten erfolgt als Median und dem 25./75. Perzentil. Ergebnisse: Vor der LPS-Challenge lagen alle Werte für SAA ≤ 2,6 mg/l. Nach der LPS-Challenge stiegen die Werte signifikant an (Angabe Median und in Klammern 25./75. Perzentil, Placebo-Gruppe: 98,4 (70,2/118) μg/ml, Zeit p = 0,008; GKE-Gruppe: 70,7 (46,8/111) μg/ml, Zeit p = 0,003). Innerhalb der GKE-Gruppe stieg der Wert für Hp im Serum nach der LPS-Challenge signifikant an (Zeit p = 0,005). Es konnten keine weiteren signifikanten Unterschiede in den Blutparametern im Vergleich der GKE-Gruppe zur Placebogruppe nach LPS Stimulation gefunden werden. Im Lebergewebe zeigte sich nach der LPS-Challenge für die GKE-Gruppe eine 2,6-fach geringere mRNA-Expression für das pro-inflammatorische Zytokin IL-1β im Vergleich zur Placebogruppe (Supplementierung p = 0,04). Die mRNA-Level von CD68 (Zeit p = 0,04) und Hp (Zeit p = 0,03) zeigten nach der LPS-Challenge im Lebergewebe einen signifikanten Anstieg innerhalb der Placebogruppe. Innerhalb der GKE-Gruppe zeigten sich keine Veränderungen durch die LPS-Challenge. Ein signifikanter Unterschied zwischen der Placebo- und der GKE Gruppe nach LPS wurde nicht gefunden. Andere Parameter im Lebergewebe, wie z.B. Transkriptionsfaktor NF-κB und die Zytokine IL-6 und TNF-α, zeigten keine signifikanten Veränderungen nach der LPS-Challenge in beiden Fütterungsgruppen. Für die Ergebnisse der Immunhistochemie konnten keine signifikanten Unterschiede in Abhängigkeit zur LPS-Challenge oder der Fütterung gezeigt werden. Schlussfolgerung: Die LPS-Challenge induzierte eine generalisierte Entzündung bei Pferden und Ponys. Die Supplementierung eines GKE für 21 Tage zeigte über die Reduktion des Entzündungsmarkers IL-1β in der Leber ein anti-inflammatorisches Potential. Andere Blut- und Leberparameter zeigten keinen Supplementierungseffekt. Somit konnte kein umfassender anti-inflammatorischer Effekt der GKE Supplementierung festgestellt werden.:1 Introduction 2 Literature review 2.1 Inflammation 2.1.1 Acute phase reaction 2.1.1.1 Serum amyloid A 2.1.1.2 Haptoglobin 2.1.1.3 Retinol-binding protein 4 2.1.2 Transcription factor NF-κB 2.1.2.1 Pro-inflammatory cytokines (Il-1β, IL-6, TNF-α) 2.1.3 Macrophages 2.1.3.1 Cluster of differentiation 68 2.2 Stress of the endoplasmic reticulum 2.2.1 Fibroblast growth factor 21 2.2.2 Activating transcription factor 4 2.3 Oxidative stress 2.4 Polyphenols 2.4.1 Green tea 2.4.2 Curcuma 2.4.3 Bioavailability 2.4.4 Anti-inflammatory effects 2.4.5 Antioxidative effects 3 Publication 3.1 Effects of a blend of green tea and curcuma extract supplementation on lipopolysaccharide-induced inflammation in horses and ponies 4 Discussion 4.1 Effects of the LPS challenge 4.1.1 Induction of inflammation by LPS 4.1.2 Induction of ER stress and oxidative stress by LPS 4.2 Effects of the GCE supplementation 4.2.1 Anti-inflammatory effects 4.2.2 Reduction of ER stress and oxidative stress 4.2.3 Comparison of in vivo effects in equines and farm animals 4.3 Daily dosages of polyphenols 4.4 Conclusion 5 Zusammenfassung 6 Summary 7 References 8 Appendix 8.1 List of presentations as part of this thesis 8.2 Further publications 8.2.1 Published articles 8.2.2 Published conference contributions 9 Acknowledgement / Introduction: Different medical conditions are linked with an inflammatory status in horses and ponies. Inflammation can be induced by endoplasmic reticulum (ER) stress, leading to an immune response which can be measured by several markers of the signalling cascade. The liver plays an important role as production site of these inflammatory markers. The influence of feeding a polyphenol-rich supplement consisting of green tea and curcumin extract (GCE) on ER stress and inflammation has been already described in several species such as cattle and pigs. Aim of the study: The aim of the study was to investigate the effect of a GCE supplementation on lipopolysaccharide (LPS)-induced inflammation in horses and ponies. It was hypothesized that the GCE supplementation will reduce inflammatory reactions and cell stress compared to the placebo group. Animals, material and methods: In a randomized, placebo controlled study, five healthy adult warmblood horses (mean (±SD) age 19 ± 5 years, mean (±SD) body weight (BW) 589 ± 81 kg) and six healthy adult Shetland ponies (mean (±SD) age 9 ± 3 years and mean (±SD) BW 126 ± 8 kg) were included. Animals were fed daily with meadow hay (2 kg/ 100 kg BW). In a cross-over design, animals were supplemented for 21 days with 10 g of a GCE (20% total polyphenol content) according to manufacturer’s instructions or a placebo (calcium carbonate) in a mixture with 1 kg (horses) or 0.2 kg (ponies) of a commercial feed for horses. After supplementation for 21 days, all animals underwent an intravenous LPS (10 ng/kg BW) challenge to induce a moderate systemic inflammation. 24 hours before and 12 hours after the LPS challenge, blood and liver samples were collected. Liver tissue was taken transcutaneously under ultrasound control. Subsequently, a 3-months-lasting wash-out period was conducted where the animals were fed with meadow hay ad libitum. A change of feeding groups according to the cross-over design was performed. A second LPS challenge and sample collection were performed according to the above-mentioned protocol. All blood samples were analysed for serum amyloid A (SAA), haptoglobin (Hp) and Retinol-binding protein 4 (RBP4). RT-qPCR was used to analyse liver mRNA levels of selected markers of inflammation (Hp, TNF-α, IL-1β, IL-6, CD68, FGF21, NF-kB, ATF4). In addition, liver tissue was histologically examined for inflammatory responses. All data except for immunohistochemical results were statistically assessed with a commercial software package (Statistica). Data were checked for normal distribution using the Shapiro-Wilks test. As data set was not normally distributed the Wilcoxon test for non-parametric data was used for analyses. Level of significance was set at P < 0.05. Data are presented as median and 25./75. percentile. Results: All SAA values before LPS were ≤ 2.6 mg/L. After LPS challenge, all SAA values were significantly higher compared to baseline (data expressed as medians and 25./75. Percentile in brackets, placebo group: 98.4 (70.2/118) μg/mL, time P = 0.008; GCE group: 70.7 (46.8/111) μg/mL, time P = 0.003). GCE group showed a significant increase for serum Hp after LPS challenge (time P = 0.005). Other significant differences in blood parameters comparing placebo and GCE group after LPS could not be found. In the liver, the pro-inflammatory cytokine IL-1β showed a 2.6-fold lower mRNA level after LPS challenge in the GCE group compared to placebo group (supplementation P = 0.04). Hepatic mRNA levels of CD68 (time P = 0.04) and Hp (time P = 0.03) increased significantly in the placebo group, but not in the GCE supplementation group. A significant difference between the two feedings groups after LPS could not be found. Other liver parameters, such as transcription factor NF-κB and the cytokines IL-6 and TNF-α, were not different after LPS challenge in both feeding groups. Immunohistochemical results showed no difference between GCE and placebo group after LPS challenge. Conclusion: The LPS challenge induced inflammation in the horses and ponies. Feeding a GCE for 21 days showed some potential to alter LPS-induced systemic inflammatory responses by reducing mRNA levels of the inflammatory marker IL-1β in liver tissue. Nevertheless, an overall anti-inflammatory effect by GCE was missing, since other blood and liver parameters were not affected by the GCE supplementation.:1 Introduction 2 Literature review 2.1 Inflammation 2.1.1 Acute phase reaction 2.1.1.1 Serum amyloid A 2.1.1.2 Haptoglobin 2.1.1.3 Retinol-binding protein 4 2.1.2 Transcription factor NF-κB 2.1.2.1 Pro-inflammatory cytokines (Il-1β, IL-6, TNF-α) 2.1.3 Macrophages 2.1.3.1 Cluster of differentiation 68 2.2 Stress of the endoplasmic reticulum 2.2.1 Fibroblast growth factor 21 2.2.2 Activating transcription factor 4 2.3 Oxidative stress 2.4 Polyphenols 2.4.1 Green tea 2.4.2 Curcuma 2.4.3 Bioavailability 2.4.4 Anti-inflammatory effects 2.4.5 Antioxidative effects 3 Publication 3.1 Effects of a blend of green tea and curcuma extract supplementation on lipopolysaccharide-induced inflammation in horses and ponies 4 Discussion 4.1 Effects of the LPS challenge 4.1.1 Induction of inflammation by LPS 4.1.2 Induction of ER stress and oxidative stress by LPS 4.2 Effects of the GCE supplementation 4.2.1 Anti-inflammatory effects 4.2.2 Reduction of ER stress and oxidative stress 4.2.3 Comparison of in vivo effects in equines and farm animals 4.3 Daily dosages of polyphenols 4.4 Conclusion 5 Zusammenfassung 6 Summary 7 References 8 Appendix 8.1 List of presentations as part of this thesis 8.2 Further publications 8.2.1 Published articles 8.2.2 Published conference contributions 9 Acknowledgement
144

Vliv epigalokatechin galátu na redukci hmotnosti - systematická rešerše / Influence of epigalokatechin gallate on weight reduction - a systematic review

Janda, Marek January 2022 (has links)
Introduction: This thesis investigates the effect of isolated epigallocatechin-3-gallate on weight reduction in the adult population. An overview of Czech and foreign literature was provided on topics of obesity, the possibility of using green tea in its treatment and the positive effects of green tea on human health, followed by a systematic review and meta-analysis. Methodology: Using a three-phase systematic search strategy, published studies were searched in the Scopus database using predefined keywords. The aim of the search was to find randomized placebo-controlled studies lasting at least 8 weeks, which examined the effect of isolated EGCG in the absence of other active substances on the change of body parameters. The extracted data from the primary studies were then evaluated using meta-analysis and forest plot. As a result, a standardized mean difference with a 95 % confidence interval was calculated using a random effect model. Results: Six1 studies met the inclusion criteria, one2 of which was excluded due to insufficient evaluation in the critical appraisal of methodological quality. The remaining 5 studies provided a total sample of 325 participants who were diagnosed with a change in BMI induced by EGCG consumption. The result was a standardized average difference of -0.01, 95 % CI:...
145

Incorporation of selected plant extracts into edible chitosan films and the effect on the antiviral, antibacterial and mechanical properties of the material

Amankwaah, Collins 08 August 2013 (has links)
No description available.
146

Effects of Climate and Atmospheric Nitrogen Deposition on Early to Mid-Term Stage Litter Decomposition Across Biomes

Kwon, TaeOh, Shibata, Hideaki, Kepfer-Rojas, Sebastian, K. Schmidt, Inger, S. Larsen, Klaus, Beier, Claus, Berg, Björn, Verheyen, Kris, Lamarque, Jean-Francois, Hagedorn, Frank, Eisenhauer, Nico, Djukic, Ika, Network, TeaComposition 11 December 2023 (has links)
Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12- month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1– 3.5% and of the more stable substrates by 3.8–10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4–2.2% and that of low-quality litter by 0.9–1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.
147

Influência do processamento, de antioxidantes e da estocagem sobre a estabilidade oxidativa lipídica do ovo / Influence of processing, antioxidants and storage on oxidative stability of egg lipids

Carvalho, Michelle Garcêz de 01 November 2012 (has links)
O ovo é consumido in natura ou processado, e usado como matéria-prima em diversos produtos. A pasteurização e a atomização são os principais processamentos aplicados ao ovo. Diferentes condições de processamento, embalagem e estocagem podem afetar a estabilidade oxidativa lipídica e reduzir a proteção antioxidante natural do ovo. O uso de embalagens onde não haja contato do ovo com a luz e oxigênio, estocagem em temperaturas baixas e uso de antioxidantes podem prevenir a oxidação lipídica. Atualmente, os antioxidantes sintéticos são cada vez mais substituídos por antioxidantes naturais ou feita uma associação entre eles. O alecrim (Rosmarinus officinalis L.) e o chá verde (Camelia sinensis L) constam entre os vegetais com grande potencial antioxidante. Com base no exposto, os objetivos do trabalho foram: a) Padronizar o método do fosfomolibdênio para avaliação da capacidade antioxidante total da fração lipídica (CATL) do ovo; b) Investigar o efeito da pasteurização e da atomização do ovo no que se refere à capacidade antioxidante e à estabilidade oxidativa da fração lipídica do ovo; c) Avaliar a estabilidade oxidativa de ácidos graxos e a capacidade antioxidante do ovo integral pasteurizado atomizado, estocado a 5ºC, por 90 dias; d) Verificar por meio de teste de concentração de antioxidantes, a estabilidade oxidativa lipídica do ovo integral pasteurizado atomizado adicionado da mistura de extrato de alecrim, extrato de chá verde e BHA (butilato de hidroxianisol); e) Otimizar a concentração da mistura de extrato de alecrim, extrato de chá verde e BHA a ser adicionada ao ovo líquido integral pasteurizado, posteriormente atomizado, pelo modelo matemático proposto pela metodologia de superfície de resposta; f) Investigar o efeito da mistura otimizada de extrato de alecrim, extrato de chá verde e BHA na estabilidade oxidativa lipídica do ovo integral pasteurizado atomizado, estocado sob as temperaturas de 5°C e 25ºC, por 90 dias. O método do fosfomolidênio para medir a CATL do ovo apresentou adequação analítica, indicada pela equação de regressão (y = 13,705x + 0,0808), coeficiente de determinação (R2 = 0,9931), limite de detecção (0,005mg &#945;-tocoferol/ mL), limite de quantificação (0,017mg &#945;-tocoferol/ mL), coeficiente de correlação (r = 0,9965), sendo que a precisão não indicou dispersão ao redor da média. A CATL diminuiu com o progresso do processamento e o inverso foi observado quanto aos lipídios, 7-CETO (7-cetocolesterol) e TBARS (substâncias reativas ao ácido tiobarbitúrico). O ovo integral pasteurizado atomizado (OIPA) mantido sob condições de estocagem consideradas ideais permaneceu estável em relação à hidratação, a CATL e as TBARS. Pelo teste de concentração de antioxidantes, foram ensaiadas dez misturas (alecrim, chá verde e BHA) no OIPA e refletiu na sua estabilidade oxidativa lipídica, verificada pelas TBARS, CATL, CT-F (capacidade redutora pelo reativo de Folin - Ciocalteau), AGL (ácidos graxos livres) e AS-233 (substâncias absorvidas a 233 nm). Os resultados mostraram que a metodologia de superfície de resposta (RSM) foi adequada para descrever a formação dos AGL e AS-233 no OIPA, podendo serem usadas para fins preditivos. A otimização da mistura de antioxidantes baseou-se no modelo matemático obtido com as AS-233, onde foi proposto como sistema antioxidante 150ppm de BHA, 600ppm de alecrim e 300ppm de chá verde. As condições de estocagem adotadas e a adição dos antioxidantes foram efetivas para manter estável o OIPA, sendo mais efetivo quando estocado a 5°C. Concluíu-se que o método do fosfomolibdênio apresentou adequação analítica. A pasteurização não afetou os parâmetros analisados (lipídios, TBARS, CATL e 7-CETO), mas a atomização provocou diminuição significativa da CATL, e elevação dos lipídios, TBARS e 7-CETO. Foi mantida a hidratação e a estabilidade oxidativa do OIPA estocado por 90 dias a 5°C, indicando que as condições de embalagem e estocagem foram efetivas. Pelo modelo matemático proposto pela RSM foi constatado que apenas os AGL e AS-233 podem ser usados para fins preditivos, optando-se pela otimização da concentração da mistura de antioxidantes, usando apenas o modelo matemático obtido nas AS-233. Com a presença ou não de antioxidantes, o OIPA estocado a 5°C, ao longo dos 90 dias, apresentou-se mais estável quanto à hidratação e à oxidação lipídica. / Egg is consumed in natura or processed and is used as raw material in various food products. The pasteurization and spray-drying processes are the main processing applied to the egg. Different processing conditions, packaging and storage can affect the lipid oxidative stability and may reduce the natural antioxidant protection of this product. The use of packages in which the egg has no contact with light and oxygen, storage at low temperatures, and the use of antioxidants can prevent lipid oxidation. Currently, synthetic antioxidants have been increasingly replaced by natural antioxidants or an association between synthetic and natural antioxidants is adopted by food companies. Rosemary (Rosmarinus officinalis L.) and green tea (Camellia sinensis L) are among the vegetables that present the highest antioxidant potential. Based on the above-mentioned considerations, the objectives of this research were: a) To standardize the method of phosphomolybdenum to evaluate the total antioxidant capacity of lipid fraction (CATL) egg; b)To investigate the effect of pasteurization and spray-drying on the antioxidant capacity and oxidative stability of the lipid fraction of egg; c) To assess the oxidative stability of fatty acids and the antioxidant capacity of whole egg subjected to pasteurization followed by spray-drying, stored at 5ºC for 90 days, d) To evaluate the by testing the concentration of antioxidants, oxidative stability of the lipid fraction of egg subjected to pasteurization and spray drying, added with a mixture of rosemary and green tea extracts and BHA (butylated hydroxyanisole); e) To optimize the concentration of the mixture composed of rosemary and green tea extracts and BHA to be added to pasteurized liquid egg (and further subjected to spray-drying) by using Response Surface Methodology; f) To investigate the effect of the addition of this optimized mixture of antioxidants on of the lipid fraction of spray-dried egg, stored at temperatures of 5 and 25°C for 90 days. The phosphomolybdenum method CATL of egg presented analytical suitability once it presented a high coefficient of determination (R2 = 0,9931), a regression equation expressed as y = 13.705 + 0.0808 x, a limit of detection of 0.005 mg &#945;- tocopherol/mL, a limit of quantitation of 0.017 mg &#945;-tocopherol/mL, a significant and high correlation coefficient (r = 0.9965), and the accuracy did not indicate dispersion around the mean. The CATL decreased with the progress of processing and the reverse was observed for the lipids, 7-CETO (7-ketocholesterol) and TBARS (thiobarbituric acid reactive substances). The pasteurized spray-dried egg (OIPA), which was kept under ideal storage conditions, remained stable in relation to moisture content, CATL and TBARS. In order to test the concentration of antioxidants to be added to OIPA, a total of 10 mixtures (rosemary, green tea and BHA) were assayed. The addition of antioxidants resulted in a higher oxidative stability of the lipid fraction as measured by TBARS, CATL, CT-F (reduction capacity by using the Folin-Ciocalteau reagent), AGL (free fat acids) and AS-233 (substances that absorb at 233 nm). The results showed that the response surface methodology (RSM) was adequate to describe the development of free fat acids and AS-233 in OIPA, and the RSM model proposed for AS-233 can be used for prediction purposes. The optimization of the antioxidant mixture based on the mathematical model proposed for AS-233 indicated that the mixture of 150ppm of BHA, 600ppm of rosemary extract and 300ppm of green tea extract was the best combination of antioxidants. The adopted storage conditions and the addition of antioxidants to OIPA were effective to maintain the response variables stable, and the stability was higher when OIPA was stored at 5°C. It was concluded that the method of phosphomolybdenum suitability presented analytically. The pasteurization did not affect the analyzed parameters (lipids, TBARS, CATL and 7-CETO), but the spray-drying caused a significant decrease CATL, and an increase in lipids, TBARS and 7-CETO. The hydration and the oxidative stability of OIPA remained stable for 90 days at 5°C, indicating that the packaging and storage conditions were effective. The RSM models proposed for free fat acids and AS-233 could be used for predictive purposes; however, the optimization procedure was performed taken into account only the AS-233 model. The OIPA stored at 5°C for 90 days, with or without the addition of the antioxidant mixture, was more stable in relation to hydration and lipid oxidation.
148

Estudo químico e avaliação da atividade antioxidante de chá-verde brasileiro (camellia sinensis var. assamica) cultivar iac-259 / Components study and antioxidant activity evaluation of Brazilian green tea (Camellia sinensis var. assamica IAC-259 cultivar)

Saito, Samuel Takashi January 2007 (has links)
O chá-verde brasileiro, obtido a partir das partes aéreas de Camellia sinensis var. assamica, teve sua produção recentemente implantada no Brasil devido ao emergente consumo. As principais atividades farmacológicas atribuídas a esta planta estão relacionadas à atividade antioxidante, quimiopreventiva e antitumoral. Neste trabalho foi desenvo lvido e validado método por cromatografia líquida de alta eficiência (CLAE) para avaliar o perfil dos constituintes majoritários [galato de epigalocatequina (EGCG), epigalocatequina, cafeína, galato de epicatequina (ECG) e epicatequina] do chá-verde brasileiro coletado na primavera e verão, e utilizando diferentes sistemas de extração. A resposta foi linear na faixa de 37-185 μg/ml para cafeína, 99-500 μg/ml para EGC, 20-100 μg/ml para catequina, 30-150 μg/ml para epicatequina, 150-800 μg/ml para EGCG, 20-105 μg/ml para galato de galocatequina e 40-205 μg/ml para ECG (r > 0,9999 para todos os compostos). Foi, também, avaliada a atividade antioxidante in vitro através do método fotocolorimétrico do DPPH· e do método enzimático da hipoxantina/xantina oxidase. Todos os sistemas de extração testados e seus respectivos extratos liofilizados apresentaram rendimento superior a 30%, sendo que o melhor sistema teve rendimento médio de 36,29%, e se mostrando mais eficiente na extração de EGCG e ECG. As amostras do verão apresentaram melhor atividade antioxidante em comparação às da primavera. Os teores dos componentes ECG e EGCG foram os únicos que correlacionaram com a atividade antioxidante in vitro (DPPH·). A análise estatística não mostrou diferença significativa (a = 0,05) nos teores de catequinas totais entre as estações primavera e verão. / The Brazilian green tea, produced from Camellia sinenis var. assamica, have been cultivated in Brazil recently because the rise at its consumption. The main pharmacological activities attributed to this plant are related to antioxidant activity as chemopreventive and anti-cancer agent. Herein, a new HPLC method was developed and validated to evaluate the profile of the major Brazilian green tea constituents [epigallocatechin gallate (EGCG), epigallocatechin, caffeine, epicatechin gallate (ECG) and epicatechin] between spring and summer, using different extraction systems. The response was linear over a range of 37-185 μg.mL-1 for caffeine, 99-500 μg.mL-1 for epigallocatechin, 20-100 μg.mL-1 for catechin, 30-150 μg.mL-1 for epicatechin, 150-800 μg.mL-1 for EGCG, 20-105 μg.mL-1 for gallocatechin gallate and 40- 205 μg.mL-1 for ECG (r > 0.9999 for all compounds). Likewise, the in vitro antioxidant activity was evaluated using DPPH· assay and hipoxanthine/xanthine oxidase assay. The extractors systems to produce the freeze-drying extract had presented yield up of 30%. The best system an average yield of 36.26% showed more efficient to extract EGCG and ECG. The summer samples presented better antioxidant activity when compared with spring samples. Only ECG and EGCG contents presented correlation with in vitro antioxidant activity (DPPH· assay). The statistic analysis did not show significant difference (a = 0.05) in total catechin content between spring and summer seasons.
149

Estudo químico e avaliação da atividade antioxidante de chá-verde brasileiro (camellia sinensis var. assamica) cultivar iac-259 / Components study and antioxidant activity evaluation of Brazilian green tea (Camellia sinensis var. assamica IAC-259 cultivar)

Saito, Samuel Takashi January 2007 (has links)
O chá-verde brasileiro, obtido a partir das partes aéreas de Camellia sinensis var. assamica, teve sua produção recentemente implantada no Brasil devido ao emergente consumo. As principais atividades farmacológicas atribuídas a esta planta estão relacionadas à atividade antioxidante, quimiopreventiva e antitumoral. Neste trabalho foi desenvo lvido e validado método por cromatografia líquida de alta eficiência (CLAE) para avaliar o perfil dos constituintes majoritários [galato de epigalocatequina (EGCG), epigalocatequina, cafeína, galato de epicatequina (ECG) e epicatequina] do chá-verde brasileiro coletado na primavera e verão, e utilizando diferentes sistemas de extração. A resposta foi linear na faixa de 37-185 μg/ml para cafeína, 99-500 μg/ml para EGC, 20-100 μg/ml para catequina, 30-150 μg/ml para epicatequina, 150-800 μg/ml para EGCG, 20-105 μg/ml para galato de galocatequina e 40-205 μg/ml para ECG (r > 0,9999 para todos os compostos). Foi, também, avaliada a atividade antioxidante in vitro através do método fotocolorimétrico do DPPH· e do método enzimático da hipoxantina/xantina oxidase. Todos os sistemas de extração testados e seus respectivos extratos liofilizados apresentaram rendimento superior a 30%, sendo que o melhor sistema teve rendimento médio de 36,29%, e se mostrando mais eficiente na extração de EGCG e ECG. As amostras do verão apresentaram melhor atividade antioxidante em comparação às da primavera. Os teores dos componentes ECG e EGCG foram os únicos que correlacionaram com a atividade antioxidante in vitro (DPPH·). A análise estatística não mostrou diferença significativa (a = 0,05) nos teores de catequinas totais entre as estações primavera e verão. / The Brazilian green tea, produced from Camellia sinenis var. assamica, have been cultivated in Brazil recently because the rise at its consumption. The main pharmacological activities attributed to this plant are related to antioxidant activity as chemopreventive and anti-cancer agent. Herein, a new HPLC method was developed and validated to evaluate the profile of the major Brazilian green tea constituents [epigallocatechin gallate (EGCG), epigallocatechin, caffeine, epicatechin gallate (ECG) and epicatechin] between spring and summer, using different extraction systems. The response was linear over a range of 37-185 μg.mL-1 for caffeine, 99-500 μg.mL-1 for epigallocatechin, 20-100 μg.mL-1 for catechin, 30-150 μg.mL-1 for epicatechin, 150-800 μg.mL-1 for EGCG, 20-105 μg.mL-1 for gallocatechin gallate and 40- 205 μg.mL-1 for ECG (r > 0.9999 for all compounds). Likewise, the in vitro antioxidant activity was evaluated using DPPH· assay and hipoxanthine/xanthine oxidase assay. The extractors systems to produce the freeze-drying extract had presented yield up of 30%. The best system an average yield of 36.26% showed more efficient to extract EGCG and ECG. The summer samples presented better antioxidant activity when compared with spring samples. Only ECG and EGCG contents presented correlation with in vitro antioxidant activity (DPPH· assay). The statistic analysis did not show significant difference (a = 0.05) in total catechin content between spring and summer seasons.
150

Estudo químico e avaliação da atividade antioxidante de chá-verde brasileiro (camellia sinensis var. assamica) cultivar iac-259 / Components study and antioxidant activity evaluation of Brazilian green tea (Camellia sinensis var. assamica IAC-259 cultivar)

Saito, Samuel Takashi January 2007 (has links)
O chá-verde brasileiro, obtido a partir das partes aéreas de Camellia sinensis var. assamica, teve sua produção recentemente implantada no Brasil devido ao emergente consumo. As principais atividades farmacológicas atribuídas a esta planta estão relacionadas à atividade antioxidante, quimiopreventiva e antitumoral. Neste trabalho foi desenvo lvido e validado método por cromatografia líquida de alta eficiência (CLAE) para avaliar o perfil dos constituintes majoritários [galato de epigalocatequina (EGCG), epigalocatequina, cafeína, galato de epicatequina (ECG) e epicatequina] do chá-verde brasileiro coletado na primavera e verão, e utilizando diferentes sistemas de extração. A resposta foi linear na faixa de 37-185 μg/ml para cafeína, 99-500 μg/ml para EGC, 20-100 μg/ml para catequina, 30-150 μg/ml para epicatequina, 150-800 μg/ml para EGCG, 20-105 μg/ml para galato de galocatequina e 40-205 μg/ml para ECG (r > 0,9999 para todos os compostos). Foi, também, avaliada a atividade antioxidante in vitro através do método fotocolorimétrico do DPPH· e do método enzimático da hipoxantina/xantina oxidase. Todos os sistemas de extração testados e seus respectivos extratos liofilizados apresentaram rendimento superior a 30%, sendo que o melhor sistema teve rendimento médio de 36,29%, e se mostrando mais eficiente na extração de EGCG e ECG. As amostras do verão apresentaram melhor atividade antioxidante em comparação às da primavera. Os teores dos componentes ECG e EGCG foram os únicos que correlacionaram com a atividade antioxidante in vitro (DPPH·). A análise estatística não mostrou diferença significativa (a = 0,05) nos teores de catequinas totais entre as estações primavera e verão. / The Brazilian green tea, produced from Camellia sinenis var. assamica, have been cultivated in Brazil recently because the rise at its consumption. The main pharmacological activities attributed to this plant are related to antioxidant activity as chemopreventive and anti-cancer agent. Herein, a new HPLC method was developed and validated to evaluate the profile of the major Brazilian green tea constituents [epigallocatechin gallate (EGCG), epigallocatechin, caffeine, epicatechin gallate (ECG) and epicatechin] between spring and summer, using different extraction systems. The response was linear over a range of 37-185 μg.mL-1 for caffeine, 99-500 μg.mL-1 for epigallocatechin, 20-100 μg.mL-1 for catechin, 30-150 μg.mL-1 for epicatechin, 150-800 μg.mL-1 for EGCG, 20-105 μg.mL-1 for gallocatechin gallate and 40- 205 μg.mL-1 for ECG (r > 0.9999 for all compounds). Likewise, the in vitro antioxidant activity was evaluated using DPPH· assay and hipoxanthine/xanthine oxidase assay. The extractors systems to produce the freeze-drying extract had presented yield up of 30%. The best system an average yield of 36.26% showed more efficient to extract EGCG and ECG. The summer samples presented better antioxidant activity when compared with spring samples. Only ECG and EGCG contents presented correlation with in vitro antioxidant activity (DPPH· assay). The statistic analysis did not show significant difference (a = 0.05) in total catechin content between spring and summer seasons.

Page generated in 0.1728 seconds