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Doctoral Thesis
DOI
10.11606/T.75.2014.tde-02022015-161613
Document
Author
Full name
Natália Ellen Castilho de Almeida
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2014
Supervisor
Committee
Cardoso, Daniel Rodrigues (President)
Boscolo, Mauricio
Colnago, Luiz Alberto
Curvelo, Antonio Aprigio da Silva
Rodrigues Filho, Edson
Title in Portuguese
Reatividade das lupulonas, terpenos, flavonoides prenilados e compostos contendo grupos tióis livre frente aos radicais formados durante o envelhecimento da cerveja
Keywords in Portuguese
cerveja
flavonoides prenilados
lupulonas
radical 1-hidroxietila
reatividade
terpenos
tióis
Abstract in Portuguese
A reatividade das lupulonas, terpenos, flavonoides prenilados e compostos contendo grupos tióis livre foi avaliada frente ao radical 1-hidroxietila (HER) para melhor conhecer o balanço redox da cerveja. As constantes de velocidade aparentes (kap) para a reação entre HER e os substratos supracitados foram obtidas via cinética de competição utilizando a armadilha química 4-POBN como competidor e monitorando-se o aduto radical formado por RPE. A partir dos valores obtidos de kap (108 L mol-1 s-1 para as lupulonas, 105 a 107 L mol-1 s-1 para terpenos, 109 L mol-1 s-1 para os flavonoides prenilados, e 108 a 109 L mol-1 s-1 para tióis) e pelas concentrações médias destes compostos na cerveja, pôde-se inferir que a extensão da degradação térmica destes compostos na bebida aumenta na ordem: lupulonas > tióis > flavonoides prenilados > terpenos. Os produtos de reação foram identificados por espectrometria de massas, e através de investigações eletroquímicas e cálculos ab initio empregando-se DFT se propôs um mecanismo de reação. Os produtos de degradação pela reação com HER foram: derivados hidroxilados e compostos de adição do radical HER para as lupulonas; derivados hidroxilados para os terpenos; derivados de adição do radical HER para os flavonoides prenilados; e dissulfetos para os tióis. Em experimento similar foram determinadas as kap para a reação entre metil ésteres derivados de ácidos graxos insaturados e esteróis com o HER, cujos valores de kap variaram de (2,7 ± 0,1) x 107 até (5,2 ± 0,1) x 107 L mol-1 s-1 para o metil docosahexanoato e ergosterol, respectivamente. Os dados cinéticos aqui obtidos contribuem para um melhor conhecimento da degradação térmica oxidativa da cerveja, bem como sugerem que os polifenóis prenilados podem conferir um significativo efeito antioxidante ao organismo humano quando do seu consumo e absorção.
Title in English
Reactivity of lupulones, terpenes, prenylated flavonoids and thiol-containing compounds towards radicals formed during the beer aging
Keywords in English
1-hydroxyethyl radical
beer
lupulones
prenylated flavonoids
reactivity
terpenes
thiols
Abstract in English
The reactivity of lupulones, terpenes, prenilated flavonoids and thiol-containing compounds was evaluated towards the 1-hydroxyethyl radical (HER) to provide a better knowledge of the redox balance of beer. The apparent rate constants (kap) for the reaction between HER and the substrates were obtained through a competitive kinetic approach using the spin-trap 4-POBN as a competitor and by monitoring the radical adduct by EPR. From the obtained values of kap (108 L mol-1 s-1 for lupulones, from 105 to 107 L mol-1 s-1 for terpenes, 109 L mol-1 s-1 for prenylated flavonoids, and from 108 to 109 L mol-1 s-1 thiol compounds) and the average concentrations of these compounds in beer, it is possible to infer that the extension of the thermal degradation on the beverage is enhanced according to: lupulones > thiol compounds > prenylated flavonoids > terpenes. The reaction products were identified by mass spectrometry, and by electrochemical investigations and ab initio (DFT) calculation, a reaction mechanism has been proposed. The degradation products for the reaction with HER were: hydroxide derivatives and HER addition products for the lupulones; hydroxide derivatives for terpenes; HER addition derivatives for prenylated flavonoids; and disulfides for thiol cmpounds. In similar experiments it was determined the kap for the reaction among methyl ester derivatives of unsaturated fatty acids and sterols with HER, with kap values ranging from (2.7 ± 0.1) x 107 to (5.2 ± 0.1) x 107 L mol-1 s-1 for the methyl docosahexanoate and ergosterol, respectively. The obtained kinetic data may contribute for a better knowledge of the thermal oxidative degradation of beer, as well as may suggest that prenylated polyphenols could present a significant antioxidant effect in the human body through its consumption and absorption.
 
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Publishing Date
2015-02-03
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • Almeida, NEC, et al. Reactivity of Beer Bitter Acids Toward the 1-Hydroxyethyl Radical as Probed by Spin-Trapping Electron Paramagnetic Resonance (EPR) and Electrospray Ionization−Tandem Mass Spectrometry (ESI−MS/MS) [doi:10.1021/jf104797d]. Journal of Agricultural and Food Chemistry [online], 2011, vol. 59, p. 4183-4191.
  • Almeida, NEC, Nascimento, E. S. P., and Cardoso, Daniel R. On the Reaction of Lupulones, Hops β-Acids, with 1-Hydroxyethyl Radical [doi:10.1021/jf302708c]. Journal of Agricultural and Food Chemistry [online], 2012, vol. 60, p. 10649-10656.
  • DE ALMEIDA, NATÁLIA E. C., et al. Beer thiol-containing compounds and redox stability: a kinetic study of 1-hydroxyethyl radical scavenging ability [doi:10.1021/jf402159a]. Journal of Agricultural and Food Chemistry [online], 2013, vol. 1, p. 130905190554001-1.
  • Almeida, NEC, et al. Reatividade e mecanismo de degradação de lupulonas frente ao radical 1-hidroxietila. In 34a. Reunião Anual da Sociedade Brasileira de Química, Florianópolis - SC, 2011. Livro de Resumos - 34a. Reunião Anual da Sociedade Brasileira de Química.São Paulo - SP : Sociedade Brasileira de Química, 2011. Resumo.
  • Almeida, NEC, and CARDOSO, D. R. Reactivity of beer bitter acids towards 1-hydroxyethyl radical as probed by spin-trapping ESI-MS. In 3o. Congresso BrMass, Campinas SP, 2009. 30. Congresso BrMass., 2009. Abstract. Available from: http://www.brmass.br.
  • Almeida, NEC, e CARDOSO, D. R. Estudo do mecanismo de degradação térmica de iso-alfa-ácidos em cerveja. In 33a Reunião Anual da Sociedade Brasilieira de Química, Águas de Lindóia - SP, 2010. Livro de Resumos - 33a Reunião Anual da Sociedade Brasilieira de Química. : Sociedade Brasilieira de Química, 2010. Resumo.
  • Almeida, NEC, e Cardoso, Daniel R. Reactivity of reduced iso-a-acids towards 1-hydroxyethyl radical as probed by spin-trapping/ESI-MS competitive kinetic approach. In VIII Brazilian Meeting on Chemistry of Food and Beverages, São Carlos - SP, 2010. Book of Abstracts - VIII Brazilian Meeting on Chemistry of Food and Beverages., 2010. Resumo.
  • Almeida, NEC, Nascimento, E. S. P., and CARDOSO, D. R. A Combined Spin-Trapping EPR and HPLC-MS Approach to Study the Reactivity of Bioactive Compounds Towards Free Radicals. In HPLC 2012: 38th International Symposium on High Performance Liquid Phase Separations and Related Techniques, Anaheim, CA, 2012. HPLC 2012: 38th International Symposium on High Performance Liquid Phase Separations and Related Techniques. : CASSS, 2012. Abstract.
  • de Almeida, Nata?lia E. C., et al. Beer redox stability conferred by thiol-containing peptides and proteins: A kinetic study of 1-hydroxyethyl radical scavenging ability. In 75th Annual Meeting of ASBC, Tucson, Arizona, US, 2013. 75th Annual Meeting of ASBC., 2013. Resumo. Dispon?vel em: http://www.asbcnet.org/meetings/pdfs/2013ProgBk.pdf.
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