On the Stability of the Bioactive Flavonoids Quercetin and Luteolin under Oxygen-Free Conditions (Articolo in rivista)

Type
Label
  • On the Stability of the Bioactive Flavonoids Quercetin and Luteolin under Oxygen-Free Conditions (Articolo in rivista) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1007/s00216-011-5504-3 (literal)
Alternative label
  • Ramesova, Sárka; Sokolová, Romana; Degano, Ilaria; Zabka, Ján; Bulícková, Jana; Gál, Miroslav (2012)
    On the Stability of the Bioactive Flavonoids Quercetin and Luteolin under Oxygen-Free Conditions
    in Analytical & bioanalytical chemistry (Print); Springer, Heidelberg (Germania)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Ramesova, Sárka; Sokolová, Romana; Degano, Ilaria; Zabka, Ján; Bulícková, Jana; Gál, Miroslav (literal)
Pagina inizio
  • 975 (literal)
Pagina fine
  • 982 (literal)
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  • 402 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali
  • 8 (literal)
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  • 2 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, v.v.i. Dolejskova 3, 18223 Prague, Czech Republic; Department of Chemistry and Industrial Chemistry, University of Pisa, Via Risorgimento 35, 56100 Pisa, Italy; (literal)
Titolo
  • On the Stability of the Bioactive Flavonoids Quercetin and Luteolin under Oxygen-Free Conditions (literal)
Abstract
  • The natural flavonoid compounds quercetin (3,3',4',5,7-pentahydroxyflavone) and luteolin (3',4',5,7-tetrahydroxyflavone) are important bioactive compounds with antioxidative, anti-allergic, and anti-inflammatory properties. However, both are unstable when exposed to atmospheric oxygen, which causes degradation and complicates their analytical determinations. The oxidative change of these flavonoids was observed and followed by UV-visible spectrophotometry, both in aqueous and ethanolic solutions. The distribution of the degradation products in aqueous media was monitored by LC-MS and LC-DAD analysis. The amounts of oxidative reaction products increase with the exposure time. The oxidative degradation reduces the pharmacological efficiency of these antioxidants and renders analytical determination inaccurate. The oxidative changes in flavonoid test solutions can explain the inconsistent dissociation constants reported in the literature. Dissociation constants of quercetin and luteolin were determined both by alkalimetric titration and by UV-visible spectrophotometry under deaerated conditions. The values pK (1) = 5.87 +/- 0.14 and pK (2) = 8.48 +/- 0.09 for quercetin, and pK (1) = 5.99 +/- 0.32 and pK (2) = 8.40 +/- 0.42 for luteolin were found. (literal)
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