Kinetic Study of Flavonoid Reactions with Stable Radicals

The antiradical activities of some flavonols (kaempferol, quercetin, robinetin, quercetagetin, and myricetin), flavones (apigenin, baicalein, and luteolin), flavanones (naringenin and dihydroquercetin), and flavanols [(+)-catechin and (−)-epicatechin] were determined by measuring the reaction kineti...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2004-05, Vol.52 (10), p.2816-2820
Main Authors: Butković, Vjera, Klasinc, Leo, Bors, Wolf
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biphenyl Compounds
Catechin - chemistry
Flavanones - chemistry
Flavonoids - chemistry
Flavonols - chemistry
Food industries
Free Radicals - chemistry
Fundamental and applied biological sciences. Psychology
General aspects
Kinetics
Methods of analysis, processing and quality control, regulation, standards
Picrates - chemistry
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Summary:The antiradical activities of some flavonols (kaempferol, quercetin, robinetin, quercetagetin, and myricetin), flavones (apigenin, baicalein, and luteolin), flavanones (naringenin and dihydroquercetin), and flavanols [(+)-catechin and (−)-epicatechin] were determined by measuring the reaction kinetics with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and α,γ-bisdiphenylene-β-phenylallyl (BDPA) radicals. The reactions, which follow the mixed second-order rate law, were investigated under pseudo-first-order conditions by use of a large excess of flavonoids, and their stoichiometry was determined by spectrophotometric titration. The results confirm stoichiometric factors of 1, 2, and 3 for flavonoids with one, two, and three hydroxyl groups in the B-ring, respectively, excluding kaempferol, which, despite a single OH group in the B-ring, has a factor of 2, which is explained by the 3-OH group supporting the reaction with free radicals. Structure−activity considerations indicate for the present series of flavonoids the importance of multiple OH substitutions and conjugation. The logarithms of reaction rate constants with the OH, DPPH, and BDPA radicals correlate well with the reduction potential of the flavonoids. Keywords: Flavonoids; antiradical activity; reaction rate constants; DPPH and BDPA radicals; correlation with reduction potential; structure−activity relationship (SAR)
ISSN:0021-8561
1520-5118
DOI:10.1021/jf049880h