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Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia e Ciência de Alimentos, Escola de Química e Alimentos, 2008. / Submitted by Caroline Silva (krol_bilhar@hotmail.com) on 2012-09-13T19:06:33Z No. of bitstreams: 1 avaliao da atividade antifngica e antimicotoxinas de extratos de farelo de arroz cebola e microalga chlorella.pdf: 988335 bytes, checksum: 8413be9e7b4208c1612064781396a048 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2012-09-24T22:59:35Z (GMT) No. of bitstreams: 1 avaliao da atividade antifngica e antimicotoxinas de extratos de farelo de arroz cebola e microalga chlorella.pdf: 988335 bytes, checksum: 8413be9e7b4208c1612064781396a048 (MD5) / Made available in DSpace on 2012-09-24T22:59:35Z (GMT). No. of bitstreams: 1 avaliao da atividade antifngica e antimicotoxinas de extratos de farelo de arroz cebola e microalga chlorella.pdf: 988335 bytes, checksum: 8413be9e7b4208c1612064781396a048 (MD5) Previous issue date: 2008 / A contaminação fúngica acarreta alterações na qualidade nutricional e no valor econômico dos produtos alimentícios podendo causar danos patológicos em plantas, animais e humanos. A identificação da atividade antifúngica e antimicotoxinas, em extratos de diferentes fontes que exibem propriedades de inibir naturalmente o crescimento de fungos e subseqüente produção de micotoxinas (metabólitos secundários produzidos por fungos toxigênicos), abre a perspectiva de empregar de forma mais eficiente os tecidos vegetais empregando-os como conservadores naturais. Entre os compostos com propriedades inibidoras de crescimento fúngico e produção de micotoxinas, naturalmente presentes em alimentos, destacam-se os compostos fenólicos, que por sua estrutura química dificultam a atividade de enzimas metabólicas de microrganismos. As matérias-primas escolhidas foram: o farelo de arroz, a cebola e a microalga Chlorella phyrenoidosa. Aos três tecidos são atribuídas propriedades funcionais, sendo que os dois primeiros são abundantes na região sul e comercializados com baixo valor agregado. A chlorella é empregada em dietas especiais como fonte de compostos bioativos especialmente aminoácidos essenciais e compostos antioxidantes. Este trabalho teve como objetivo determinar o teor de compostos fenólicos, a atividade antifúngica sobre o desenvolvimento dos fungos dos gêneros Rhyzopus sp., Aspergillus oryzae, Aspergillus flavus, e Fusarium graminearum e a atividade antimicotoxinas sobre o fungo Aspergillus flavus, em extratos de farelo de arroz, cebola e Chlorella. Os compostos fenólicos da cebola foram extraídos em três sistemas solventes: aquoso, metanólico e acetato de etila. Os compostos fenólicos do farelo de arroz e da chlorella foram extraídos com metanol, sendo quantificados colorimetricamente com reagente de Folin-Ciocalteau. O conteúdo de fenóis totais nos vegetais variou de 68 μgfenóis.g-1 em extrato aceto-etílico de cebola a 3012 μgfenóis.g-1 em extrato aquoso de cebola. Os extratos foram triados sobre os fungos Rhyzopus sp e Aspergillus oryzae que foram os modelos para estimar a inibição de crescimento fúngico. Esporos de Aspergillus flavus foram utilizados para estudar o efeito inibidor da produção de aflatoxina B1 e B2. Os extratos testados apresentaram algum grau de inibição do desenvolvimento fúngico, sendo a chlorella a que apresentou maior inibição em relação aos outros extratos, em todos os fungos testados, chegando a 31% de inibição/μg fenol total. Após o 7°, 14° e 21° dia de incubação foram realizadas extrações de micotoxinas do meio de crescimento pelo método adaptado de TANAKA et al., (2000). O extrato fenólico de Chlorella inibiu totalmente a produção de micotoxinas em relação ao controle. Estes resultados mostram que a ação antifúngica está naturalmente presente em alguns tecidos vegetais e que encontrar a forma de extraí-los e aplicá-los como conservadores de alimentos é muito promissor para agregar valor aos alimentos, principalmente aqueles de baixo valor comercial. / The fungal contamination cause alterations in nutritional quality and economic value of food products and can cause pathological damages in plants, animals and humans. The identification of the antifungal activity and antimycotoxin in extracts of sources different that show properties of naturally inhibiting the fungal growth and subsequent mycotoxins production (metabolites secondary produced by toxic fungal), open the perspective of employing in the more efficient form the vegetable tissue employing them like natural conservatives. Between compounds with properties inhibiting of fungal growth and mycotoxins production, naturally present in foods, stand out the phenolics, what for your chemical structure make difficult the activity of metabolic enzymes of microrganisms. The chosen raw materials were: the rice bran, the onion and the microalga Chlorella phyrenoidosa. To three tissues functional properties are attributed being that two first ones are abundant in the south region and marketed with low collected value. The Chlorella is employed in special diets like source of bioactives compounds and antioxidant compounds. This objective study was determine the tenor of phenolics compounds, the antifungal activity on the development of the fungal Rhyzopus sp, Aspergillus oryzae, Aspergillus flavus and Fusarium graminearum and antimycotoxin activity on the fungal Aspergillus flavus, in extracts of bran of rice, onion and Chlorella. The phenolic compounds of the onion were extracted in three solvent systens: aqueous, methanolic and ethila acetate. The phenolic compounds of the bran of rice and of the Chlorella were extracted with methanol, and quantified with reagent of Folin-Ciocalteau. The total phenolics levels in vegetables ranged between 68 μgphenolicg-1 in aceto-ethylic extract of anion and 3012 μgphenolic g-1 in aqueous extract of onion. The extracts was used in antifungal tests against strains of Rhyzopus sp and Aspergillus oryzae that were the models to appreciate the inhibition of fungal growth. Spores of Aspergillus flavus were used to study the inhibiting effect of the aflatoxins B1 and B2 production. The tested extracts presented some degree of inhibition of the fungal development, being the Chlorella Who presented tested bigger inhibition regasding other extracts, in all the fungal, is reaching 31% of inhibition/μgphenolic . After 7°, 14 and 21° Day of incubation were carried out extractions of mycotoxins from growth médium were determined by TANAKA et al., method (2000). The phenolic extract of chlorella inhibited totally the mycotoxins production regarding the control. These results show that the antifungal activity is present naturally in some vegetable tissues and that to find the formo of extracting to apply as conservatives of foods is very promising to values collect to the foods, principally those of low commercial value.

Sorghum grains contain phenolic compounds that have been shown to have many favourable effects. In this study the levels of phenolic compounds in condensed tannin and condensed tannin-free sorghums have been determined and the antimicrobial activity of phenolic extracts from bran fractions of the respective sorghums has been further evaluated against pathogenic bacteria Bacillus cereus ATCC 1178, Escherichia coli ATCC 25922 and Listeria monocytogenes ATCC 7644. Defatted bran fractions prepared from a condensed tannin sorghum variety (red) and a condensed tannin-free sorghum variety (white) were analysed for their content of total phenols and condensed tannins. Total phenols were determined using the Folin-Ciocalteu method and condensed tannins with the vanillin-HCL method. Total phenols and condensed tannins of the bran fractions were extracted with aqueous acetone (75 % v/v) and acidified methanol (1% HCL v/v in methanol) respectively, using a bran-to-solvent ratio of 1:4 (w/v). Red sorghum bran contained a higher amount of total phenols and condensed tannins (33.18 mg tannic acid equivalent/g and 117.98 mg catechin equivalent/g of the bran fractions, respectively) than white sorghum bran (6.81 mg tannic acid equivalent/g and 8.52 mg catechin equivalent/g of the bran fractions, respectively). Freeze-dried sorghum crude phenolic extracts (CPE) obtained from defatted bran fractions of condensed tannin and condensed tannin-free sorghum varieties were evaluated for their antimicrobial activities against Bacillus cereus ATCC 1178, Escherichia coli ATCC 25922 and Listeria monocytogenes ATCC 7644 pathogenic bacteria. The extracts were tested at 1, 2, 4 and 20 % concentrations (w/v) in methanol using the paper disc diffusion method and absolute methanol was used as a control. The condensed tannin-free sorghum CPE at concentrations 1, 2 and 4 % had no inhibitory effects on the bacteria tested but was effective against Gram-positive bacteria, B. cereus ATCC 1178 and L. monocytogenes ATCC 7644 at a concentration of 20 %. The condensed tannin sorghum CPE was effective against B. cereus ATCC 1178 and L. monocytogenes ATCC 7644 at concentrations 1 , 2 , 4 and 20 %. None of the tested sorghum extracts inhibited the Gram-negative bacteria, E. coli ATCC 25922. Phenolic extracts from condensed tannin sorghum may be used as antimicrobial agents to prevent the growth of Gram-positive bacteria, B. cereus ATCC 1178 and L. monocytogenes ATCC 7644. / Dissertation (MSc (Food Science and Technology))--University of Pretoria, 2007. / Food Science / unrestricted

Please read the abstract in the section 00front of this document Copyright 1997, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beta, T 1997, Processing of polyphenol-rich sorghums for food, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-08032007-125938 / > / Thesis (PhD (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2016 / In this study, antioxidant activity methodologies were evaluated in terms of analytical performances. The total antioxidant activity from Athrixia phylicoides leaves (Bush tea) determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH•) method, cupric ion reducing power (CUPRAC) method and cyclic voltammetry (CV). Folin-Ciocalteu method was used to quantify total phenolic content (TPC) in Athrixia phylicoides leaves. The influence of chemical and physical parameters on the total phenolic content and antioxidant activity determination were investigated. Results from direct sample and crude sample were compared. Antioxidant activity and phenolic content from Athrixia phylicoides leaves were compared with those from commercialised green tea, black tea and rooibos tea using two chosen antioxidant capacity method with acceptable characteristics. Results from the evaluation of the methods demonstrated excellent recoveries (99 to 103%) consistently, good linearity within the calibration concentration range (R2 = 0.997) and repeatable low coefficient of variation < 5% were indicative of good precision except for CV method. The average total antioxidant activity of various extracts of Athrixia phylicoides leaves ranged from 0.039 to 0.122 mg/mL (EC50), 0.031 to 0.233 mg/mL (EC50) and 339 to 429 mV (anodic potential) for DPPH method, CUPRAC method and CV method, respectively. The total antioxidant activity values for each Athrixia phylicoides samples determined by CUPRAC method were higher than the values produced by DPPH and CV methods. The highest antioxidant activities in the DPPH and CUPRAC methods were found in water extracts (direct sample). However, concentrated samples for DPPH method and CV gave a different trend with the methanol extract (crude sample) displaying the highest antioxidant capacity. Increasing the infusion time only increased total antioxidant activity determined by CUPRAC method, whilst DPPH and CV methods had the highest antioxidant activity in the lowest infusion time (3 min). Even though the results are inconclusive with regard to the effect of solid to solvent ratio effect on the total antioxidant activity, 1:150 ratio and 1:100 ratio extracts for both CUPRAC and DPPH methods and for CV gave the highest antioxidant capacities, respectively. The total antioxidant activities in pure antioxidant standards and in the teas were ranked in the following order by both CUPRAC and DPPH methods: Quercetin > catechin > Trolox and Chinese green tea > Joko black tea > Athrixia phylicoides leaves > Laager rooibos tea, respectively. Comparative study showed the necessity of employing more than one method, as each method for the same sample yielded different results. CUPRAC and DPPH methods displayed higher sensitivity and repeatability as compared to the CV method with poor precision.

Thesis (MSc. (Chemistry)) -- University of Limpopo, 2016 / In this study, antioxidant activity methodologies were evaluated in terms of analytical performances. The total antioxidant activity from Athrixia phylicoides leaves (Bush tea) determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH•) method, cupric ion reducing power (CUPRAC) method and cyclic voltammetry (CV). Folin-Ciocalteu method was used to quantify total phenolic content (TPC) in Athrixia phylicoides leaves. The influence of chemical and physical parameters on the total phenolic content and antioxidant activity determination were investigated. Results from direct sample and crude sample were compared. Antioxidant activity and phenolic content from Athrixia phylicoides leaves were compared with those from commercialised green tea, black tea and rooibos tea using two chosen antioxidant capacity method with acceptable characteristics. Results from the evaluation of the methods demonstrated excellent recoveries (99 to 103%) consistently, good linearity within the calibration concentration range (R2 = 0.997) and repeatable low coefficient of variation < 5% were indicative of good precision except for CV method. The average total antioxidant activity of various extracts of Athrixia phylicoides leaves ranged from 0.039 to 0.122 mg/mL (EC50), 0.031 to 0.233 mg/mL (EC50) and 339 to 429 mV (anodic potential) for DPPH method, CUPRAC method and CV method, respectively. The total antioxidant activity values for each Athrixia phylicoides samples determined by CUPRAC method were higher than the values produced by DPPH and CV methods. The highest antioxidant activities in the DPPH and CUPRAC methods were found in water extracts (direct sample). However, concentrated samples for DPPH method and CV gave a different trend with the methanol extract (crude sample) displaying the highest antioxidant capacity. Increasing the infusion time only increased total antioxidant activity determined by CUPRAC method, whilst DPPH and CV methods had the highest antioxidant activity in the lowest infusion time (3 min). Even though the results are inconclusive with regard to the effect of solid to solvent ratio effect on the total antioxidant activity, 1:150 ratio and 1:100 ratio extracts for both CUPRAC and DPPH methods and for CV gave the highest antioxidant capacities, respectively. The total antioxidant activities in pure antioxidant standards and in the teas were ranked in the following order by both CUPRAC and DPPH methods: Quercetin > catechin > Trolox and Chinese green tea > Joko black tea > Athrixia phylicoides leaves > Laager rooibos tea, respectively. Comparative study showed the necessity of employing more than one method, as each method for the same sample yielded different results. CUPRAC and DPPH methods displayed higher sensitivity and repeatability as compared to the CV method with poor precision.

Edible pulse seeds are good sources of food ingredients. Germination has been regarded as an effective process to further improve nutrient digestibility and accessibility of pulse seeds. Our aim was to observe the effect of germination on proximate composition, physicochemical attributes, and phenolic profiles of chickpea (Cicer arietinum L.), lentil (Lens culinaris Merr.), and yellow pea (Pisum sativum L.). In addition, mechanisms of how germination affects the antioxidant activity of phenolic compounds were proposed. Chemical composition, thermal, pasting, and moisture adsorption properties of pulse flours were investigated over 6 days of germination. Protein contents increased by 3 percent points for all pulses over germination. However, lentil had the highest protein content. Lipid contents decreased over germination with chickpea having the greatest decline, from 8.00 to 5.90 g/100g (d.b.). Total starch decreased in lentil and yellow pea during germination. Thermal properties of pulse flours changed slightly, while pasting properties varied among pulses. The highest final viscosities for chickpea, lentil, and yellow pea flours were 1061, 981, and 1052 cP and were observed after 2, 1, and 0 days of germination, respectively. Moisture adsorption isotherms showed improved water adsorption capabilities after germination. Soluble free (SFPs) and polar soluble bound phenolic compounds (PSBPs) were extracted from germinated pulse seeds. Their antioxidant activities were evaluated using both the in vitro system and stripped soybean oil (SSO)-in-water emulsions. Liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry and size-exclusion chromatography with multiangle-light-scattering and refractive-index detection were employed to analyze the phenolic composition and molar mass, respectively. Antioxidant activities of SFPs increased in both in vitro and SSO-in-water emulsion system, however, much lower than those of PSBPs based on SSO-in-water emulsion system. The effect of germination on PSBPs in SSO-in-water emulsion varied between pulses. By virtue of chemometric analysis, nine phenolic compounds were speculated as the pivotal phenolic compounds responsible for the antioxidant activity of PSBPs. In particular, the molar masses of PSBPs had a positive relationship with their antioxidant activity. Protective and co-antioxidative principles were proposed as reasons for the variability of antioxidant activities of PSBPs in oil-in-water emulsions with germination. / Hatch project number ND01593

<p> It has been shown that the hydroxy compounds la-4a possess triplet states which are substantially shorter-lived than those of their methoxy analogs (lb-4b). In each case the efficient quenching of the excited carbonyl triplet state has been attributed to intramolecular phenolic hydrogen abstraction. Evidence for this is found in the detection of biradical species generated from triplet decay, primary hydrogen-deuterium kinetic isotope effects and thermodynamic parameters which support both atom transfer (enthalpy) and high degrees of order (entropy) in the transition state necessary for the proposed abstraction process. The difference in triplet lifetimes (16 ns to 1135 ns) is due almost exclusively to varying degrees of difficulty in obtaining a transition state geometry in which the phenoxy hydrogen is properly lined up for intramolecular hydrogen abstraction. </p> / Thesis / Master of Science (MSc)

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