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Academic literature on the topic 'Polyphenol'

Author: Grafiati

Published: 4 June 2021

Last updated: 22 June 2023

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Journal articles on the topic "Polyphenol"

Maisto, Maria, Elisabetta Schiano, Ettore Novellino, Vincenzo Piccolo, Fortuna Iannuzzo, Emanuela Salviati, Vincenzo Summa, Giuseppe Annunziata, and Gian Carlo Tenore. "Application of a Rapid and Simple Technological Process to Increase Levels and Bioccessibility of Free Phenolic Compounds in Annurca Apple Nutraceutical Product." Foods 11, no. 10 (May 17, 2022): 1453. http://dx.doi.org/10.3390/foods11101453.

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Insoluble bound polyphenols (ISBP) are polyphenolic compounds linked to the food matrix with different interactions limiting both their water extractability and consequent bioaccessibility. The health-promoting potential of polyphenols is historically known and well-demonstrated; specifically, Annurca apple polyphenols were studied both in vitro and in vivo for their effect in controlling cholesterol plasma levels. The aim of the study was the preparation of nutraceutical products based on Annurca apple polyphenolic fraction through the application of a technological process (acid treatment) able to release the ISBP from Annurca apple food matrix and increase polyphenol bioaccessibility. Lyophilized annurca apple (LAA) underwent acid treatment (ATLAA), and differences in released polyphenol levels were analysed by DAD-HPLC. Free-polyphenol levels in samples treated under acid conditions were higher than in untreated ones; in particular, for oligomeric flavan-3-ols (+168% procyanidin B2, +42.97% procyanidin B1 and B2, +156.99% procyanidin C1), catechin (+512.20%), and gallic acid (+707.77%). Furthermore, ATLAA underwent an in vitro gastrointestinal digestion to evaluate the bioaccessibility of contained polyphenols, in comparison to the untreated Annurca apple. The bioaccessibility study indicates a valuable preservation of polyphenolic fraction compared to the control.

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McDougall, Gordon J. "Phenolic-enriched foods: sources and processing for enhanced health benefits." Proceedings of the Nutrition Society 76, no. 2 (November 2, 2016): 163–71. http://dx.doi.org/10.1017/s0029665116000835.

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Polyphenols are ubiquitous secondary products present in many plant foods. Their intake has been associated with health benefits ranging from reduced incidence of CVD, diabetes and cancers to improved neurodegenerative outcomes. Major dietary sources include beverages such as coffee, teas and foods such as chocolate. Fruits are also major sources and berries in particular are a palatable source of a diverse range of polyphenol components. There are a number of ways that polyphenol uptake could be increased and healthier polyphenol-rich foods could be produced with specific compositions to target-specific health effects. Firstly, we could exploit the genetic diversity of plants (with a focus on berries) to select varieties that have enhanced levels of specific polyphenols implicated in disease mitigation (e.g. anthocyanins, tannins or flavonols). Working with variation induced by environmental and agronomic factors, modern molecular breeding techniques could exploit natural variation and beneficially alter polyphenol content and composition, although this could be relatively long term. Alternatively, we could employ a synthetic biology approach and design new plants that overexpress certain genes or re-deploy more metabolic effort into specific polyphenols. However, such ‘polyphenol-plus’ fruit could prove unpalatable as polyphenols contribute to sensorial properties (e.g. astringency of tannins). However, if the aim was to produce a polyphenol as a pharmaceutical then ‘lifting’ biosynthetic pathways from plants and expressing them in microbial vectors may be a feasible option. Secondly, we could design processing methods to enhance the polyphenolic composition or content of foods. Fermentation of teas, cocoa beans and grapes, or roasting of cocoa and coffee beans has long been used and can massively influence polyphenol composition and potential bioactivity. Simple methods such as milling, heat treatment, pasteurisation or juicing (v. pureeing) can have notable effects on polyphenol profiles and novel extraction methods bring new opportunities. Encapsulation methods can protect specific polyphenols during digestion and increase their delivery in the gastrointestinal tract to target-specific health effects. Lastly we could examine reformulation of products to alter polyphenol content or composition. Enhancing staple apple or citrus juices with berry juices could double polyphenol levels and provide specific polyphenol components. Reformulation of foods with polyphenol-rich factions recovered from ‘wastes’ could increase polyphenol intake, alter product acceptability, improve shelf life and prevent food spoilage. Finally, co-formulation of foods can influence bioavailability and potential bioactivity of certain polyphenols. Within the constraints that certain polyphenols can interfere with drug effectiveness through altered metabolism, this provides another avenue to enhance polyphenol intake and potential effectiveness. In conclusion, these approaches could be developed separately or in combination to produce foods with enhanced levels of phenolic components that are effective against specific disease conditions.

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Akhter, A., S. Zaman, U. Ali, Y. Ali, and M. A. Jalil Miah. "Isolation of Polyphenolic Compounds from the Green Coconut (cocos nucifera) Shell and Characterization of their Benzoyl Ester Derivatives." Journal of Scientific Research 2, no. 1 (December 29, 2009): 186–90. http://dx.doi.org/10.3329/jsr.v2i1.2659.

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Polyphenolic compounds were isolated from the aqueous extract of green coconut shell. Benzoyl ester derivatives were prepared with these polyphenols. Monobenzoyl and dibenzoyl derivatives of a polyphenol were separated and characterized. Keywords: Green coconut shell; Cocos nucifera; Polyphenol. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i1.2659 J. Sci. Res. 2 (1), 186-190 (2010)

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Jakobek, Lidija, Martina Skendrović Babojelić, Jasmin Lesičar, Jasna Šic Žlabur, Sandra Voća, Ivana Buljeta, and Jozo Ištuk. "Polyphenol content, profile, and distribution in old, traditional apple varieties." Croatian journal of food science and technology 12, no. 1 (May 29, 2020): 110–17. http://dx.doi.org/10.17508/cjfst.2020.12.1.14.

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Apples are an important source of polyphenols in the human diet. They have also shown many potentially beneficial effects on human health. Old, traditional apple varieties grown in the past could also be valuable varieties but little is known about their polyphenolic compounds and characteristics in general. The aim of this study was to collect 25 old, traditional apple varieties, to determine their polyphenolic profile and the amounts of total polyphenols in the peel and flesh, and to compare them with a commercial variety. To the best of our knowledge, some of those varieties have never been studied before (‘Mašanka’, ‘Bobovac’, ‘Batulenka’, ‘Krastavka’). Total polyphenols were determined by using the Folin-Ciocalteu method and individual polyphenol identification was done by using an RP-HPLC. The flesh contained 170 to 941 mg kg-1 fresh weight (FW) of total polyphenols, and the peel contained 931 to 3791 mg kg-1 FW. In comparison to the commercial variety, the peel of all old varieties had higher polyphenol content, while the flesh of only some old varieties was richer in polyphenols. Principal component analysis showed possible clustering. Eighteen individual polyphenols were distributed in apple peel and flesh. The dominant polyphenol subgroups in the peel were flavonols (18 to 80 %) and flavan-3-ols (6 to 66 %), and in the flesh those subgroups were phenolic acids (41 to 85 %) and flavan-3-ols (3-49 %).

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Vasantha Rupasinghe, H. P., and Chris Kean. "Polyphenol concentrations in apple processing by-products determined using electrospray ionization mass spectrometry." Canadian Journal of Plant Science 88, no. 4 (July 1, 2008): 759–62. http://dx.doi.org/10.4141/cjps07146.

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Liquid chromatography coupled with electrospray ionization and triple quadrupole mass spectrometry (ESI-MS/MS) was used to determine the concentrations of polyphenols in apple processing by-products collected from commercial juice and pie manufacturing plants. Apple pomace (cultivar Gravenstein) resulting from juice processing contained a total polyphenol concentration of 43 mg 100 g-1 dry matter (DM), and was mainly constituted of phloridzin and quercetin-3-O-galactoside. The major polyphenolic compound in apple seeds (cultivar Idared) was phloridzin (64 mg 100 g-1 DM), representing 84% of total polyphenols (76 mg 100 g-1 DM). The predominant polyphenolic compounds in apple cores (cultivar Idared) were phloridzin, chlorogenic acid, and epicatechin, which represented 77% of the total polyphenols (40 mg 100 g-1 DM). The total polyphenol concentrations in the skin of Northern Spy and Idared were 322 and 401 mg 100 g-1, respectively. The major polyphenol sub-classes detected in apple skins were flavonols (151-154 mg 100 g-1 DM), dihydrochalcones (48-59 mg 100 g-1 DM), flavan-3-ols (32-38 mg 100 g-1 DM), phenolic acids (40-59 mg 100 g-1 DM) and anthocyanins (29-114 mg 100 g-1 DM). Key words: Malus × domestica, apple, polyphenols, flavonoids, by-products, LC-MS/MS

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Kalompatsios, Dimitris, Vassilis Athanasiadis, Dimitrios Palaiogiannis, Stavros I. Lalas, and Dimitris P. Makris. "Valorization of Waste Orange Peels: Aqueous Antioxidant Polyphenol Extraction as Affected by Organic Acid Addition." Beverages 8, no. 4 (November 7, 2022): 71. http://dx.doi.org/10.3390/beverages8040071.

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Waste orange peels (WOP) are a food processing residue rich in bioactive polyphenols. However, data on aqueous extraction processes for efficient polyphenol recovery are rather limited. The present study dealt with the optimization of WOP polyphenols, using a batch stirred-tank mode and water as solvent. After a preliminary single-factor examination, the implementation of response surface methodology revealed that optimum extraction time and temperature were 60 min and 55 °C, respectively. Under these conditions, the extraction afforded a total polyphenol yield of 26.13 ± 0.78 mg gallic acid equivalents per g dry mass. The use of aqueous solutions of citric, tartaric and lactic acid showed that total polyphenol yield may be significantly increased with 1% tartaric acid or equally with 2.5% citric acid. However, the effect on individual polyphenolic constituents was rather negligible, as determined by high-performance liquid chromatography. The discrepancies observed in the antioxidant properties of the extracts produced with water and acidified water were putatively attributed to some differences in the polyphenolic composition. The extraction methodology proposed is environmentally green and of low cost, and it could certainly be used as an effective means of recovering WOP polyphenols.

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Lakka, Achillia, Stavros Lalas, and Dimitris P. Makris. "Hydroxypropyl-β-Cyclodextrin as a Green Co-Solvent in the Aqueous Extraction of Polyphenols from Waste Orange Peels." Beverages 6, no. 3 (August 10, 2020): 50. http://dx.doi.org/10.3390/beverages6030050.

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There is, to-date, an expanding interest concerning the use of cyclodextrins as green food-grade co-solvents in the aqueous extraction of polyphenols, however, data regarding polyphenol extraction from waste orange peels (WOP) are lacking. On this ground, hydroxypropyl β-cyclodextrin (HP-β-CD), a highly water-soluble cyclodextrin, was used to develop a simple and straightforward methodology for the effective recovery of WOP polyphenols. Process optimization by response surface showed that maximum total polyphenol recovery (26.30 ± 1.49 mg gallic acid equivalents g−1 dry mass) could be accomplished with 15 mM HP-β-CD at 40 °C. On the other hand, integration of ultrasonication pretreatment was found unsuitable, as it resulted in reduced polyphenol yield. Examination of solvent acidity indicated that polyphenol extraction may be enhanced at pH 4, but the difference was non-significant (p > 0.05) compared to yields attained at pH 2, 3, and 5. Extraction of WOP polyphenols with HP-β-CD was shown to provide significantly higher hesperidin yield compared to 60% (v/v) aqueous ethanol, which suggested selectivity of HP-β-CD toward this polyphenolic metabolite.

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Lachman, J., M. Orsák, and V. Pivec. "Antioxidant complex of bioflavonoids and ascorbic acid in apples (Malus pumila Mill.) – a review." Czech Journal of Food Sciences 18, No. 4 (January 1, 2000): 153–58. http://dx.doi.org/10.17221/8335-cjfs.

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In this review article it is given an information about the composition of flavonoid complex of apples (Malus pumila Mill.). It is discussed the influence of extrinsic and intrinsic factors on polyphenolic antioxidant content (varietal differences, influence of locality, year, maturity, pre-harvest treatment, storage, technological ways of processing) and the relation between the polyphenol content and the resistance of apple varieties. During storage there is an apparent decrease of both ascorbic acid and polyphenols. Contents of anthocyanins and chalcones are in positive correlation with resistance of apple trees to low and variable temperatures. During maturation of apple fruits synthesis and accumulation of polyphenols, esp. anthocyanins, and ascorbic acid was determined. Meanwhile polyphenols are substrates of polyphenol oxidases in the process of enzymic browning, ascorbic acid is a natural inhibitor of this browning deterioration. Process of enzymic browning of apple fruits and juices could be inhibited with ascorbic and citric acid addition to apple products. Polyphenol content could be influenced by pre-harvest and technological procedures.

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Clarke, Erin D., Megan E. Rollo, Clare E. Collins, Lisa Wood, Robin Callister, Mark Philo, Paul A. Kroon, and Rebecca L. Haslam. "The Relationship between Dietary Polyphenol Intakes and Urinary Polyphenol Concentrations in Adults Prescribed a High Vegetable and Fruit Diet." Nutrients 12, no. 11 (November 9, 2020): 3431. http://dx.doi.org/10.3390/nu12113431.

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Urinary polyphenol metabolites are potential biomarkers of dietary polyphenol intake. The current study aims to evaluate associations between total diet, vegetable and fruit polyphenol intakes with urinary polyphenol metabolite concentrations in a sample of adults prescribed a diet rich in vegetables and fruit. Thirty-four participants completed a 10-week pre-post study. Participants were asked to consume Australian recommended daily vegetable and fruit serves and attend measurement sessions at baseline and at weeks 2 and 10. Two 24-h diet recalls were collected at each time-point and polyphenol intakes were calculated using the Phenol-Explorer database. Spot urine samples, collected at each time-point, were analyzed for 15 polyphenol metabolites using liquid chromatography-mass spectroscopy. Spearman’s correlation analyzes assessed the strength of relationships between urinary and dietary polyphenols. Linear mixed models were used to investigate relationships between polyphenol excretion and intake. Total urinary polyphenols were significantly correlated with total polyphenol intakes at week 10 (rs = 0.47) and fruit polyphenols at week 2 (rs = 0.38). Hippuric acid was significantly correlated with vegetable polyphenols at baseline (rs = 0.39). Relationships were identified between individual polyphenol metabolites and vegetable and fruit polyphenols. Linear mixed model analyzes identified that for every 1 mg increase in polyphenol intakes, urinary polyphenol excretion increased by 16.3 nmol/g creatinine. Although the majority of relationships were not sufficiently strong or consistent at different time-points, promising relationships were observed between total urinary polyphenols and total polyphenol intakes, and hippuric acid and vegetable polyphenols.

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Fayeulle, Noémie, Sébastien Preys, Jean-Michel Roger, Renaud Boulanger, Clotilde Hue, Véronique Cheynier, and Nicolas Sommerer. "Multiblock Analysis to Relate Polyphenol Targeted Mass Spectrometry and Sensory Properties of Chocolates and Cocoa Beans." Metabolites 10, no. 8 (July 29, 2020): 311. http://dx.doi.org/10.3390/metabo10080311.

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Chocolate quality is largely due to the presence of polyphenols and especially of flavan-3-ols and their derivatives that contribute to bitterness and astringency. The aim of the present work was to assess the potential of a quantitative polyphenol targeted metabolomics analysis based on mass spectrometry for relating cocoa bean polyphenol composition corresponding chocolate polyphenol composition and sensory properties. One-hundred cocoa bean samples were transformed to chocolates using a standard process, and the latter were attributed to four different groups by sensory analysis. Polyphenols were analyzed by an ultra-high-performance liquid chromatography (UPLC) system hyphenated to a triple quadrupole mass spectrometer. A multiblock method called a Common Component and Specific Weights Analysis (CCSWA) was used to study relationships between the three datasets, i.e., cocoa polyphenols, chocolate polyphenols and sensory profiles. The CCSWA multiblock method coupling sensory and chocolate polyphenols differentiated the four sensory poles. It showed that polyphenolic and sensory data both contained information enabling the sensory poles’ separation, even if they can be also complementary. A large amount of variance in the cocoa bean and corresponding chocolate polyphenols has been linked. The cocoa bean phenolic composition turned out to be a major factor in explaining the sensory pole separation.

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Dissertations / Theses on the topic "Polyphenol"

Warminski, Edward Edmund. "Polyphenol-protein precipitation." Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324615.

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JoÌˆbstl, Elisabeth. "Polyphenol interactions in tea." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408304.

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Rooney, C. "Polyphenol intake, dietary patterns and psychological status." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680508.

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Increasing evidence has suggested that dietary consumption may have the potential to influence mental health. However, few experimental studies have examined the effect of polyphenol-rich foods on psychological health. Furthermore, minimal studies exist on consumer attitudes towards polyphenol-rich foods. Thus, the main aims of this thesis were to investigate the effect of polyphenol-rich foods (FV, berries and dark chocolate) on psychological health, and to examine the behaviours, attitudes and knowledge consumers have with regards to the consumption of these foods. Firstly, results from a systematic review suggested that current evidence surrounding fruit and vegetables (FV) and psychological well-being is inconclusive. The review highlighted the need for future randomised controlled trials to investigate the relationship further. Secondly, a randomised controlled trial (PPhIT) showed mixed findings with regards to the effect of an eight week polyphenol-rich dietary pattern (FV, berries and dark chocolate) on psychological health. Improvements were observed for certain outcomes, including depressed mood and mental health (quality of life), but not for others (e.g. self-esteem and body-image). The dietary intervention led to significant increases in nutritional biomarkers, indicating good participant compliance. Overall, participants showed favourable attitudes towards the polyphenol-rich diet. Whilst a number of barriers towards the study diet foods were detected at baseline, the intervention significantly reduced some of these (e.g. ease, willingness, awareness). Similarly, a second ReT (n=30 adults), highlighted various barriers and facilitators towards FV consumption. However, in contrast to PPhIT, the four week intervention did not significantly modify these. This study also detected a lack of knowledge regarding what constitutes a portion of FV. The inconsistent findings from this thesis surrounding the effect of polyphenol-rich foods on psychological health suggest further research is warranted. Future research on the capacity for dietary interventions to reduce barriers towards polyphenol-rich foods may also be of value.

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Omar, Ulfat Mohammed. "The bioactive properties of pomegranate polyphenol (Punicalagin)." Thesis, University of Surrey, 2014. http://epubs.surrey.ac.uk/810111/.

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Plant polyphenols are reported to have bioactive properties, which may be used for protection against diseases. Therefore, the aim of this research was to investigate the bioactive activities of a pomegranate tannin polyphenol compound, punicalagin. In particular, the antioxidant, antihypertensive and anticancer mechanisms were investigated. Punicalagin was found III pomegranate husk but not in pomegranate juice when analysed by HPLC and LC-MS. Antioxidant mechanisms involved hydrogen peroxide scavenging, ferrous chelating and reducing ability. Higher hydrogen peroxide scavenging activity was achieved by 0.1 mg/ml from both punicalagin and pomegranate juice when compared with butylated hydroxytoluene (BHT) or trolox (p :S0.05). Punicalagin and pomegranate juice exhibited ferrous chelating ability significantly lower than Ethylenediaminetetraacetic acid. Cell toxicity induced by tert-butylhydroperoxide (3 mM) was significantly inhibited by punicalagin (5 and 10 !!M) in Caco-2 cells; these results were confinned by cell morphology. Punicalagin protection was achieved by inhibiting cellular reactive oxygen species (ROS) as well as malondialdehyde levels. Glutathione level was significantly increased in stressed cells pretreated with both concentration of punicalagin, indicating good antioxidant activity for punicalagin. Punicalagin (1-60 !!M) increased nitric oxide production in endothelial cells (EA.hy926) through decreased ROS levels and increased endothelial nitric oxide synthase enzyme (eNOS) activation. Activation of eNOS enzyme was achieved by an II - increase of cellular calcium concentration. At the same examined concentration of punicalagin (1-60 f-tM), the activity of angiotensin converting enzyme (ACE) was significantly inhibited. The dual action of punicalagin as nitric oxide synthase inducer and ACE inhibitor showed antihypertensive effect. Punicalagin (50 and 75 f-tM) showed toxic effects on the colon cancer cell line (Caco-2) but not on a normal colon cell line (HCEC); both results were confinned by morphological studies. In the presence of punicalagin, cytoplasmic ROS production decreased, indicating antioxidant activity whereas superoxide radicals released from mitochondria increased due to mitochondrial dysfunction. Annexin V and caspase family (caspase 9, 8 and 3) activation confinned that cell death occurred via apoptosis pathway by both concentrations of punicalagin. The cell cycle was attested by punicalagin in the G liS-phase at the concentrations tested. The above findings indicating that punicalagin has antioxidant, antihypertensive and anticarcinogenic activity.

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Burton, Stephanie Gail. "Biocatalytic and biomimetic studies of polyphenol oxidase." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1004088.

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Mushroom polyphenol oxidase (EC 1.14.18.1) was investigated to determine its potential for application as a biocatalyst in the synthesis of o-quinones, in organic medium. In order to determine the kinetic properties of the biocatalyst, a system was devised which comprised an immobilised polyphenol oxidase extract, functioning in chloroform. The system was hydrated by the addition of buffer. A simple method for the consistent measurement of reaction rates in this heterogenous system was designed and used to obtain detailed enzyme kinetic data relating to optimisation of reaction conditions and substrate specificity. The aqueous content of the system was optimised using p-cresol as a substrate. A crude, immobilised extract of Agaricus bisporus was used to hydroxylate and oxidise a range of selected p-substituted phenolic substrates, yielding, as the sale products, o-quinones. These products were efficiently reduced to catechols by extracting the reaction mixtures with aqueous ascorbic acid solution. The biocatalytic system was also successfully utilised to produce L-DOPA, the drug used to treat Parkinson's disease, from L-acetyl tyrosine ethyl ester (ATEE). Michaelis-Menten kinetics were used to obtain apparent Km and V values with respect to the selected phenolic substrates, and the kinetic parameters obtained were found to correlate well with the steric requirements of the substrates and with their hydrophobicity. In the course of the investigation, a novel ¹H NMR method was used to facilitate measurement of the UV molar absorption coefficients of the o-quinones in reaction mixtures, thus avoiding the necessity to isolate these unstable, water-sensitive products. The biocatalytic system was extended to a continuous process, in which the immobilised enzyme was shown to function successfully in the chloroform medium for several hours, with high conversion rates. Modifications, involving partial purification and the addition of a surfactant, were investigated to determine their effect on the kinetic parameters. The results obtained using partially purified enzyme indicated that the removal of extraneous protein and/or melanoid material lead to a reduced capacity for conversion of sterically demanding substrates. The addition of the anionic detergent, sodium dodecyl sulphate (SOS), enhanced the ability of the biocatalyst to bind and oxidise sterically demanding substrates. These effects are attributed to changes in the polar state of groups within the protein binding pocket, which result in altered flexibility and hydrophobicity. Computer modelling of several biomimetic dinuclear copper complexes also indicated the importance of flexibility for effective biocatalysis. Novel binuclear copper (II complexes, containing a flexible biphenyl spacer and imidazole or benzimidazole donors, were prepared and analysed using NMR, UV, AA and cyclic voltammetric techniques. The complexes were also shown, in a detailed kinetic study, to mimic the catecholase activity of polyphenol oxidase by oxidising 3,5-di-tertbutylcatechol, and to catalyse the coupling of the phenolic substrate 2,4-di-tert-butylphenol. However, the complexes were apparently too flexible to react with smaller substrates. These biomimetic complexes provided valuable insights into the nature of the dinuclear copper binding site.

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Molina, Bacca Aurora Esther <1990&gt. "Olive Mill Wastewater Valorisation Through Polyphenol Adsorption." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7396/1/Molina_Bacca_Aurora_Esther_Tesi.pdf.

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Due to the negative environmental impact of the Olive Mill Wastewaters (OMW), research is done in order to treat and valorize them. In this work, different OMW from different Italian regions (Liguria and Puglia) and harvests (from 2012 to 2014) were tested in order to recover polyphenols (PCs), molecules with a high added value because of their beneficial properties. The solid phase used for PCs recovery was the resin Amberlite XAD16; the desorption solvent was acidified ethanol. An HPLC method for total PCs content quantification was developed using a C18 column. A new, repeatable and reliable column packing method was developed. The packing quality was evaluated with step-change fluid dynamic analysis tests using NaCl 0.04M as tracer. Also, to avoid clogging problems in the packed columns an OMW pre-treatment was designed, capable to remove 98% of the solids. Several breakthrough tests were performed to evaluate the influence of linear velocity and column length (0.52m and 2.0m). A repeatability test was performed in order to evaluate the stability of the process. The process was modeled using a plug flow with axial dispersion model with solid-liquid mass transfer; implemented in COMSOL3.5a. The desorption curves were obtained with subsequent solvent regeneration. Antioxidant activity tests were performed with the desorption product using the ABTS method. On the basis of economic considerations, two new ion-exchange resins were tested (IRA958Cl and IRA 67Cl). IRA958Cl showed the best performance. Two breakthrough tests at different linear velocities were conducted with this resin. In order to recover specific high added value molecules (tyrosol and hydroxytyrosol) from the actual OMW, experiments were performed in collaboration with the Fachhoschule Nordwestschweiz (FHNW) using a Cyclodextrin-based polyurethane polymer, synthetized by the FHNW research group. Then, in order to increase the purity of tyrosol in the desorption fractions several organic solvents were tested.

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Ibars, Serra Maria. "Polyphenol effects on central leptin sensitivity in obesity." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/457127.

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L’obesitat és un problema de salut en augment i suposa un risc per al desenvolupament de malalties cròniques. Les estratègies per reduir i prevenir l’obesitat no han sigut satisfactòries el que fa necessari el desenvolupament d’alternatives terapèutiques. Nombrosos estudis en animals i humans demostren que els polifenols tenen propietats protectores en front a trastorns metabòlics per la qual cosa aquests compostos bioactius poden ser útils per a reduir l’obesitat i malalties metabòliques associades. La leptina és una hormona encarregada de la regulació del balanç energètic al sistema nerviós central on activa les neurones POMC i inhibeix les AgRP produint sacietat i promovent la despesa energètica. No obstant això, l’acció de la leptina en l’obesitat es troba afectada. L’objectiu principal d’aquesta tesi és identificar polifenols que millorin la sensibilitat a la leptina en situacions d’obesitat i que tingui com a resultat la pèrdua de pes. En aquesta tesi demostrem com el consum crònic d’un extracte de pinyol de raïm ric en proantocianidines millora la senyalització de la leptina a través de l’augment de l’expressió gènica del neuropèptid POMC i redueix la ingesta energètica sense mostrar canvis al pes corporal. A més, s’ha investigat el potencial d’altres polifenols amb efectes complementaris a les proantocianidines per tal d’estimular la pèrdua de pes. Els resultats presentats mostren que el resveratrol és efectiu reduint el pes i el greix corporal i la hiperleptinèmia en animals obesos, actuant com a agent sensibilitzador de la leptina. D’altra banda, es demostra el potencial de fruites estacionals riques en polifenols en la modulació de la senyalització de la leptina en condicions normals i d’obesitat. Finalment, s’explica el rol d’una nova diana per modular l’activitat neuronal de les neurones AgRP. Els resultats d’aquesta recerca aporten nous coneixements pel disseny d’aliments funcionals que combinin diferents compostos bioactius amb el potencial de poder ser utilitzats com a teràpia anti-obesitat.
La obesidad es un problema de salud en aumento y supone un riesgo para el desarrollo de enfermedades crónicas. Las estrategias para reducir y prevenir la obesidad no han sido satisfactorias lo que hace necesario el desarrollo de alternativas terapéuticas. Numerosos estudios en animales y humanos demuestran que los polifenoles tienen propiedades protectoras frente a trastornos metabólicos por lo que estos compuestos bioactivos pueden ser útiles para reducir la obesidad y enfermedades metabólicas asociadas. La leptina es una hormona encargada de la regulación del balance energético en el sistema nervioso central donde activa las neuronas POMC e inhibe las AgRP produciendo saciedad y promoviendo el gasto energético. Sin embargo, la acción de la leptina en la obesidad se encuentra afectada. El objetivo principal de esta tesis es identificar polifenoles que mejoren la sensibilidad a la leptina en situaciones de obesidad y que tenga como resultado la pérdida de peso. En esta tesis demostramos como el consumo crónico de un extracto de pepita de uva rico en proantocianidinas mejora la señalización de la leptina a través del aumento de la expresión génica del neuropéptido POMC y reduce la ingesta energética sin mostrar cambios en el peso corporal. Además, se ha investigado el potencial de otros polifenoles con efectos complementarios a las proantocianidinas para estimular la pérdida de peso. Los resultados presentados muestran que el resveratrol es efectivo reduciendo el peso y la grasa corporal y la hiperleptinémia en animales obesos, actuando como agente sensibilizador de la leptina. Por otra parte, se demuestra el potencial de frutas estacionales ricas en polifenoles en la modulación de la señalización de la leptina en condiciones normales y de obesidad. Finalmente, se explica el rol de una nueva diana para modular la actividad neuronal de las neuronas AgRP. Los resultados de esta investigación aportan nuevos conocimientos para el diseño de alimentos funcionales que combinen diferentes compuestos bioactivos con el potencial de poder ser utilizados como terapia anti-obesidad.
Obesity is an increasing health problem and a major risk factor for a number of chronic diseases. Up to now, strategies to reduce and prevent obesity were unsuccessful. Therefore, novel approaches to treat obesity need to be developed. In this sense, several animal and human studies demonstrate that polyphenols protect against metabolic disorders including diabetes and cardiovascular disease. Thus, polyphenols emerge as bioactive compounds useful to reduce obesity and its associated metabolic diseases. Energy balance is regulated by leptin in the central nervous system, particularly in the hypothalamus where it activates POMC and inhibits AgRP neurons to produce satiety and promote energy expenditure. However, leptin action appears to be suppressed in obesity which is reflected by increased appetite and reduced energy expenditure. The aim of this thesis was to identify polyphenols that improve leptin sensitivity under obesogenic environments, which could ultimately result in a loss of body weight. We show that a chronic intake of a grape seed proanthocyanidin extract improves leptin signaling by increasing POMC gene expression and reduces food intake without decreasing body weight in obese animals. Furthermore, we investigated other polyphenols that could complement the effects of proanthocyanidins by enhancing body weight loss. Our results show that high doses of resveratrol effectively reduce body weight, fat mass and correct hyperleptinemia in obese animals acting as a leptin sensitizer compound. Additionally, we demonstrate the potential of seasonal fruits rich in polyphenols to modulate hypothalamic leptin signaling and downstream effectors in normal conditions and during obesity. Finally, the role of a novel target to modulate AgRP neurons activity is explained. The outcome of this research provides insights into the design of functional foods that combine bioactive compounds which could potentially be used as anti-obesity therapy.

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Boshoff, Aileen. "The biotransformation of phenolic pollutants using polyphenol oxidase." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1004035.

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The potential of using mushroom polyphenol oxidase (EC 1.14.18.1) as a biocatalyst for the biotransformation of phenols to produce catechols in an aqueous medium was investigated. Polyphenol oxidase is characterised by two distinct reactions i.e., the ortho-hydroxylation of phenols to catechols (cresolase activity) and the subsequent oxidation of catechols to orthoquinones (catecholase activity). In order to facilitate the development of a process to produce catechols, the accumulation of catechol as a true intermediate product released in the reaction system needed to be investigated, as its release had been disputed due to the oxidation of catechols to o-quinones. Using LC-MS, catechol products were successfully identified as true intermediate products formed during biocatalytic reactions in water.

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Ferrari, Paola. "Designing novel colloidal materials from polyphenol-polymer complexes." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:3b16509b-12bd-40e1-a55a-f795a405eda6.

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This thesis explores the utilization of physico-chemical interactions between natural polyphenols and biocompatible polymers to design novel materials and complex colloidal dispersions and emulsions. These usually unwanted interactions and the resulting insoluble complexes are important in the creation of structures that could potentially be used in the design of novel foodstuffs. The theme of this thesis is therefore the interactions of polyphenols with polymers and emulsion stability and properties. The results are as follows. Chapter 3 presents a study on the interaction of polymer-polyphenol and the fabrication of new colloidal particles using the self-association of polymer-polyphenol complexes. The phase diagram of the physical appearance of mixtures of polyvinylpyrrolidone (PVP) with catechins and tannic acid has been explored and we have characterized the different structures by using a combination of light microscopy, UV-Vis and IR spectroscopy and dynamic light scattering techniques. The molar ratio between polymers and polyphenols has been found to play an important role in defining the structure of the complexes and their stability. By further optimizing the reaction conditions it is possible to obtain various structures resulting in colloids, microgels, and macroscopically gelled interfaces, which find applications in emulsion stabilization as explored in the following chapters. In Chapter 4 emulsification techniques and consideration on emulsion stability and formulation are investigated. Novel biodegradable surfactant free emulsions stabilized by non-covalently associated micro-gel particles made from PVP and TA have been successfully prepared. The strong interaction between PVP and TA, driven by hydrophobic interactions and hydrogen bonding between phenolic and pyrrolidinone rings, leads to formation of microgels during the emulsification process. The molar ratio between TA and PVP was found to play an important role in determining the mechanism of emulsion stabilisation. At low molar ratio a shell of PVP-TA microgels is formed and over time wrinkles have been observed on these shells, while at high molar ratio [TA]/[PVP] we observe Pickering emulsions stabilised by microgel particles and the continuous phase is a dispersion of microgel particles. The structure and stability of the systems have been investigated by light scattering, confocal and light transmission microscopy. The presence of TA leads to halochromism of the emulsions at high pH and the absence of surfactants makes these emulsions particularly desirable in terms of biodegradability. Chapter 5 focuses on the rheological properties of emulsions stabilised by gel particles and on the relationship between oil volume fraction and rheological behaviour. The rheological properties of emulsions and complex fluids are of pivotal importance in relation to their technical applications. These properties depend strongly on the emulsions composition, oil-phase volume fraction, microscopic droplet structure, and interfacial interactions. Our rheological tests showed that PVP-TA particles stabilised emulsions behave like flocculated dispersions and polymeric gels confirming the qualitative observation on emulsion gelation observed in the experiments carried out in the previous chapter. Chapter 6 introduces a new technique, microfluidics. Microfluidics devices were designed and built with the purpose of making monodisperse emulsions stabilized by PVP-TA complexes. The emulsions produced with microfluidics devices were found to be monodisperse rather than the polydisperse ones resulting from bulk emulsification processes. The basic theory behind the effect of microfluidic scaling affects the hydrodynamics is outlined. Experimental details on the design process and on how to use photo-lithography and soft-lithography to build microfluidics devices are given. Finally we have demonstrated how our microfluidics devices can be successfully used to make monodisperse emulsions stabilised by PVP-TA and double emulsions (oil in water in oil emulsions).

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Books on the topic "Polyphenol"

United States. National Aeronautics and Space Administration., ed. The tribological behavior of polyphenol ether and polyphenol thioether aromatic lubricants. [Washington, DC]: National Aeronautics and Space Administration, 1987.

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Romani, Annalisa, Vincenzo Lattanzio, and Stéphane Quideau, eds. Recent Advances in Polyphenol Research. Chichester, UK: John Wiley & Sons, Ltd, 2014. http://dx.doi.org/10.1002/9781118329634.

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Jukanti, Aravind. Polyphenol Oxidases (PPOs) in Plants. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-5747-2.

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Cheynier, Véronique, Pascale Sarni-Manchado, and Stéphane Quideau, eds. Recent Advances in Polyphenol Research. Oxford, UK: Wiley-Blackwell, 2012. http://dx.doi.org/10.1002/9781118299753.

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Daayf, Fouad, and Vincenzo Lattanzio, eds. Recent Advances in Polyphenol Research. Oxford, UK: Wiley-Blackwell, 2008. http://dx.doi.org/10.1002/9781444302400.

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Halbwirth, Heidi, Karl Stich, Véronique Cheynier, and Stéphane Quideau, eds. Recent Advances in Polyphenol Research. Chichester, UK: John Wiley & Sons, Ltd, 2019. http://dx.doi.org/10.1002/9781119427896.

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Yoshida, Kumi, Véronique Cheynier, and Stéphane Quideau, eds. Recent Advances in Polyphenol Research. Chichester, UK: John Wiley & Sons, Ltd, 2017. http://dx.doi.org/10.1002/9781118883303.

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Patel, Usha R. Polyphenol oxidase activity assay based on fibre optics. Manchester: UMIST, 1997.

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Hemingway, Richard W., and Peter E. Laks, eds. Plant Polyphenols. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3476-1.

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Book chapters on the topic "Polyphenol"

Pengelly, Andrew. "Polyphenols - tannins and flavonoids." In The constituents of medicinal plants, 41–58. 3rd ed. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789243079.0003.

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Abstract Polyphenol compounds are those with two or more benzene rings, with varying degrees of hydroxylation in each ring. The name has become almost synonymous with dietary antioxidants. In this chapter, readers were introduced to lignans and stilbenes, both examples of polyphenol compounds. The focus of this chapter is on the two largest subcategories of polyphenols such as tannins and flavonoids.

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Whitaker, John R. "Polyphenol Oxidase." In Food Enzymes, 271–307. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4757-2349-6_9.

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Haslam, Edwin, Terence H. Lilley, Edward Warminski, Hua Liao, Ya Cai, Russell Martin, Simon H. Gaffney, Paul N. Goulding, and Genevieve Luck. "Polyphenol Complexation." In ACS Symposium Series, 8–50. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0506.ch002.

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Steffens, John C., Eitan Harel, and Michelle D. Hunt. "Polyphenol Oxidase." In Genetic Engineering of Plant Secondary Metabolism, 275–312. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2544-8_11.

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Marquès, L., A. Fleuriet, and J. J. Macheix. "Fruit Polyphenol Oxidases." In ACS Symposium Series, 90–102. Washington, DC: American Chemical Society, 1995. http://dx.doi.org/10.1021/bk-1995-0600.ch007.

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Cai, Ya, Simon H. Gaffney, Terence H. Lilley, and Edwin Haslam. "Carbohydrate — Polyphenol Complexation." In Chemistry and Significance of Condensed Tannins, 307–22. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-7511-1_19.

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Lewis, Norman G., and Laurence B. Davin. "Stereo Selectivity in Polyphenol Biosynthesis." In Plant Polyphenols, 73–95. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3476-1_5.

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Baik, B. K., S. E. Ullrich, and Z. Quinde-Axtell. "Polyphenols, Polyphenol Oxidase, and Discoloration of Barley-Based Food Products." In Color Quality of Fresh and Processed Foods, 388–414. Washington, DC: American Chemical Society, 2008. http://dx.doi.org/10.1021/bk-2008-0983.ch027.

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Billaud, C., E. Regaudie, N. Fayad, Florence Richard-Forget, and Jacques Nicolas. "Effect of Cyclodextrins on Polyphenol Oxidation Catalyzed by Apple Polyphenol Oxidase." In ACS Symposium Series, 295–312. Washington, DC: American Chemical Society, 1995. http://dx.doi.org/10.1021/bk-1995-0600.ch023.

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Heim, Kelly C. "Natural Polyphenol and Flavonoid Polymers." In Antioxidant Polymers, 23–53. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118445440.ch2.

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Conference papers on the topic "Polyphenol"

Felicia, Suciu, Roșca Adrian Cosmin, Lupu Carmen, Popescu Antoanela, and Badea Victoria. "DETERMINATION OF POLYPHENOLIC COMPOUNDS OF LYSIMACHIA NUMMULARIA L." In GEOLINKS Conference Proceedings. Saima Consult Ltd, 2021. http://dx.doi.org/10.32008/geolinks2021/b1/v3/08.

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"The history of medicinal plants is associated with the evolution of civilization. In all regions of the world, the history of nations shows that these plants have always occupied an important place in medicine, in cosmetic products, and culinary preparations. The paper aims to determine the total polyphenols in different parts of the species Lysimachia nummularia L. In our study, we focused on the extraction of polyphenolic compounds in different solvents. The solvents used in the extraction were: 40% ethanol, concentrated methanol, in water. The total polyphenol content was determined by spectrophotometric methods, a method from the European Pharmacopoeia 10.0, with minor modifications. The total polyphenol content of different extracts varied depending on the extraction process. Different parts of the plant and different solvents were used in the determinations carried out to establish the optimal extraction method for the organs of Lysimachia nummularia L."

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Sharifimehr, Shahrzad, Supratim Ghosh, and Ramaswami Sammynaiken. "Development of Protein–polyphenol Conjugates via Free Radical Grafting Method: Evaluation of Physicochemical and Functional Properties." In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/bpzg5215.

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Lipid oxidation is a common phenomenon in emulsions that can be controlled by different techniques. Since proteins are beneficial emulsifiers but with low antioxidant ability, they are used in combination with an antioxidant compound such as polyphenols. Strong interaction between the protein and the polyphenol makes this combination more effective. In this study, soluble fraction of faba protein concentrate (FPC) was conjugated with tannic acid via the free radical grafting, and the structural and functional characteristics of the conjugates were determined in comparison with the mixture of the protein and tannic acid, and the pure protein. After dialysis, the amount of protein and polyphenol from the conjugated materials was significantly reduced, indicating that the unreacted peptides and polyphenol left the solutions. The reduction of the free amino and thiol groups in the protein specified the establishment of a strong interaction between the protein and tannic acid remaining in the solution. Moreover, the conjugate showed high ABTS, hydroxyl radical scavenging activity and ferric reducing power than the protein alone. As the purpose of making the conjugate was to be used as a multilayer film around the oil droplets, the film formation ability of the conjugates was investigated using Langmuir-Blodgett technique. Depending on the size of the trough and the nature of the compounds being used, the concentration and surface pressure required to form a strong film will vary. All samples showed an extended gas state of the film that changed abruptly and directly into a solid state below a critical surface area. Such LB film of the protein-tannic acid conjugate will be used to test its free radical scavenging ability so that its ability to prevent lipid oxidation in emulsions can be predicted.

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Gratl, V., E. Zini, T. Letschka, M. Stefanini, R. Velasco, S. Vezzulli, S. Sturm, and H. Stuppner. "Polyphenol composition of disease-resistant grapevine hybrids." In 67th International Congress and Annual Meeting of the Society for Medicinal Plant and Natural Product Research (GA) in cooperation with the French Society of Pharmacognosy AFERP. © Georg Thieme Verlag KG, 2019. http://dx.doi.org/10.1055/s-0039-3399842.

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Mapelli, Sergio, Gianpiero Ventimiglia, Cesare Sala, and Silvana Castelli. "Biogas Production from Exhausted Pomace after Polyphenol Recovery." In 2019 7th International Renewable and Sustainable Energy Conference (IRSEC). IEEE, 2019. http://dx.doi.org/10.1109/irsec48032.2019.9078239.

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Panasyuk, A. L., E. I. Kuzmina, and O. S. Egorova. "ENSURING OF PINK WINES STABILITY TO POLYPHENOL TURBIDITY." In Aktualnye voprosy industrii napitkov. Izdatelstvo i tipografiya "Kniga-memuar", 2018. http://dx.doi.org/10.21323/978-5-6041190-3-7-2018-2-100-103.

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Ottombrino, A., F. Fratianni, and F. Nazzaro. "Antibacterial properties of polyvinyl alcohol-rosemary polyphenol blends." In MICROBES IN APPLIED RESEARCH - Current Advances and Challenges. WORLD SCIENTIFIC, 2012. http://dx.doi.org/10.1142/9789814405041_0041.

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Czosnowska, Barbara, and Magdalena Franczyk-Żarów. "Determination of total polyphenol content in fermented products." In 2nd International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland: ENVIRONMENT – PLANT – ANIMAL – PRODUCT. Publishing House of The University of Life Sciences in Lublin, 2023. http://dx.doi.org/10.24326/icdsupl2b002.

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XIA, Wen-xu, Ping ZHAO, Jia-bin WANG, Zhan-juan LI, and Nanju Alice LEE. "Antimicrobial Activities of Polyphenol Extract of Peanut Skins." In 2nd International Conference on Biomedical and Biological Engineering 2017 (BBE 2017). Paris, France: Atlantis Press, 2017. http://dx.doi.org/10.2991/bbe-17.2017.35.

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Keyhani, Jacqueline, and Ezzatollah Keyhani. "Polyphenol oxidase in golden chanterelle (Cantharellus cibarius) mushroom." In Proceedings of the III International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2009). WORLD SCIENTIFIC, 2010. http://dx.doi.org/10.1142/9789814322119_0025.

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Bellaga, S., L. Ben Haj Said, and K. Allaf. "Partial drying of apple fruits to improve freeze/thaw quality during long term frozen storage." In 21st International Drying Symposium. Valencia: Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/ids2018.2018.8372.

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Apple samples were submitted to partially drying prior to freezing. Then, quality assessments were achieved in order to evaluate the quality of these various frozen samples during frozen-storage. Significant positive effects of water content were observed on thaw exudate water and total color difference of dehydrofrozen/thawed apples. Total polyphenol content and total flavonoid content losses were important for samples without any dehydration pretreatment. They noticeably decreased when water content decreased during the whole period of storage. Thus, a partial removal of water prior to freezing is a relevant way to maintain the stability of fruit quality during long-term frozen-storage. Keywords: Apple fruits; dehydrofreezing; frozen storage; color; polyphenol

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Reports on the topic "Polyphenol"

Wu, Joseph M. Cellular Targets of Dietary Polyphenol Resveratrol. Fort Belvoir, VA: Defense Technical Information Center, September 2006. http://dx.doi.org/10.21236/ada462814.

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Steffens, John C., and Eithan Harel. Polyphenol Oxidases- Expression, Assembly and Function. United States Department of Agriculture, January 1995. http://dx.doi.org/10.32747/1995.7571358.bard.

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Polyphenol oxidases (PPOs) participate in the preparation of many plant products on the one hand and cause considerable losses during processing of plant products on the other hand. However, the physiological functions of plant PPO were still a subject of controversy at the onset of the project. Preliminary observations that suggested involvement of PPOs in resistance to herbivores and pathogens held great promise for application in agriculture but required elucidation of PPO's function if modulation of PPO expression is to be considered for improving plant protection or storage and processing of plant products. Suggestions on a possible role of PPO in various aspects of chloroplast metabolism were also relevant in this context. The characterization of plant PPO genes opened a way for achieving these goals. We reasoned that "understanding PPO targeting and routing, designing ways to manipulate its expression and assessing the effects of such modifications will enable determination of the true properties of the enzyme and open the way for controlling its activity". The objective of the project was to "obtain an insight into the function and biological significance of PPOs" by examining possible function(s) of PPO in photosynthesis and plant-pest interactions using transgenic tomato plants; extending our understanding of PPO routing and assembly and the mechanism of its thylakoid translocation; preparing recombinant PPOs for use in import studies, determination of the genuine properties of PPOs and understanding its assembly and determining the effect of PPO's absence on chloroplast performance. Results obtained during work on the project made it necessary to abandon some minor objectives and devote the effort to more promising topics. Such changes are mentioned in the 'Body of the report' which is arranged according to the objectives of the original proposal. The complex expression pattern of tomato PPO gene family was determined. Individual members of the family are differentially expressed in various parts of the plant and subjected to developmentally regulated turnover. Some members are differentially regulated also by pathogens, wounding and chemical wound signals. Wounding systemically induces PPO activity and level in potato. Only tissues that are developmentally competent to express PPO are capable of responding to the systemic wounding signal by increased accumulation of PPO mRNA. Down regulation of PPO genes causes hyper susceptibility to leaf pathogens in tomato while over expression regulation of PPO expression in tomato plants is their apparent increased tolerance to drought. Both the enhanced disease resistance conferred by PPO over expression and the increased stress tolerance due to down regulation can be used in the engineering of improved crop plants. Photosynthesis rate and variable fluorescence measurements in wild type, and PPO-null and over expressing transgenic tomato lines suggest that PPO does not enable plants to cope better with stressful high light intensities or reactive oxygen species. Rather high levels of the enzyme aggravate the damage caused under such conditions. Our work suggests that PPO's primary role is in defending plants against pathogens and herbivores. Jasmonate and ethylene, and apparently also salicylate, signals involved in responses to wounding and defense against herbivores and pathogens, enhance markedly and specifically the competence of chloroplasts to import and process pPPO. The interaction of the precursor with thylakoid membranes is primarily affected. The routing of PPO shows other unusual properties: stromal processing occurs in two sites, resulting in intermediates that are translocated across thylakoids by two different mechanisms - a DpH- and a Sec-dependent one. It is suggested that the dual pattern of processing and routing constitutes a'fail safe' mechanism, reflecting the need for a rapid and flexible response to defense challenges. Many of the observations described above should be taken into consideration when manipulation of PPO expression is contemplated for use in crop improvement.

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Castillo-Pichardo, Linette. Grape Polyphenol Signaling to Regulate Breast Cancer Metastasis. Fort Belvoir, VA: Defense Technical Information Center, September 2009. http://dx.doi.org/10.21236/ada516581.

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Harvey, Benjamin G., Michael E. Wright, Andrew G. Guenthner, Scott Compel, Matthew Davis, Kevin Lamison, Lee Cambrea, Heather Meylemans, Sean McCormick, and Thomas Groshens. Cyanate Ester Composite Resins Derived from Renewable Polyphenol Sources. Fort Belvoir, VA: Defense Technical Information Center, March 2011. http://dx.doi.org/10.21236/ada557386.

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Ghosh, Pooja, Sultana Parveen, Susmitnarayan Chaudhury, and Swagata Dasgupta. Polyphenol loaded nanoparticles as antiglycating agents: A case study with human serum albumin. The Israel Chemical Society, March 2023. http://dx.doi.org/10.51167/acm00041.

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Lamartiniere, Coral A. Polyphenols and Prostate Cancer Chemoprevention. Fort Belvoir, VA: Defense Technical Information Center, March 2005. http://dx.doi.org/10.21236/ada437686.

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Lamartiniere, Coral A. Polyphenols and Prostate Cancer Chemoprevention. Fort Belvoir, VA: Defense Technical Information Center, April 2007. http://dx.doi.org/10.21236/ada472702.

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Lamartiniere, Coral A. Polyphenois and Prostate Cancer Chemoprevention. Fort Belvoir, VA: Defense Technical Information Center, March 2006. http://dx.doi.org/10.21236/ada460489.

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Steffens, John, Eithan Harel, and Alfred Mayer. Coding, Expression, Targeting, Import and Processing of Distinct Polyphenoloxidases in Tissues of Higher Plants. United States Department of Agriculture, November 1994. http://dx.doi.org/10.32747/1994.7613008.bard.

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Polyphenol oxidase (PPO) catalyzes the oxidation of phenols to quinones at the expense of O2. PPOs are ubiquitous in higer plants, and their role in oxidative browning of plant tissues causes large annual losses to food production. Despite the importance of PPOs to agriculture, the function(s) of PPOs in higher plants are not understood. Among other roles, PPOs have been proposed to participate in aspects of chloroplast metabolism, based on their occurrence in plastids and high Km for O2. Due to the ability of PPO to catalyze formation of highly reactive quinones, PPOs have also been proposed to be involved in a wide array of defensive interactions with insect, bacterial, and fungal pests. Physiological and biochemical studies of PPO have provided few answers to the major problems of PPO function, subcellular localization, and biochemical properties. This proposal achieved the following major objectives: cloning of PPO cDNAs in potato and tomato; characterization of the tomato PPO gene family; antisense downregulation of the tomato PPO gene family; and reduction in post-harvest enzymic browning of potato through expression of antisense PPO genes under the control of tuber-specific promoters. In addition, we established the lumenal localization of PPO, characterized and clarified the means by which PPOs are imported and processed by chloroplasts, and provided insight into the factors which control localization of PPOs. This proposal has thereby provided fundamental advances in the understanding of this enzyme and the control of its expression.

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Cobrinik, David E. Effect on Green Tea Polyphenols on Breast Cancer Signaling. Fort Belvoir, VA: Defense Technical Information Center, April 1999. http://dx.doi.org/10.21236/ada367380.

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