Relationship Between the Structures of Flavonoids and Oxygen Radical Absorbance Capacity Values: A Quantum Chemical Analysis

Various radical-scavenging activities (RSA) assessment assays are based on discrete mechanisms and on using different radical sources. Few studies have analyzed the structural significance of flavonoids in their peroxyl radical activities in the oxygen radical absorbance capacity (ORAC) assay. In th...

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Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-02, Vol.117 (8), p.1784-1794
Main Authors: Zhang, Di, Liu, Yixiang, Chu, Le, Wei, Ying, Wang, Dan, Cai, Shengbao, Zhou, Feng, Ji, Baoping
Format: Article
Language:English
Subjects:
Absorbance
Assaying
Assessments
Atomic and molecular physics
Catalytic Domain
Electronics
Enthalpy
Exact sciences and technology
Flavonoids
Flavonoids - chemistry
Fluorescence and phosphorescence
radiationless transitions, quenching (intersystem crossing, internal conversion)
Molecular properties and interactions with photons
Molecular Structure
Oxidation
Physics
Quantum Theory
Radiationless transitions, quenching
Radicals
Reactive Oxygen Species - chemistry
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Summary:Various radical-scavenging activities (RSA) assessment assays are based on discrete mechanisms and on using different radical sources. Few studies have analyzed the structural significance of flavonoids in their peroxyl radical activities in the oxygen radical absorbance capacity (ORAC) assay. In this study, the RSA of 13 flavonoids in two ORAC assays with different probes (fluorescein and pyrogallol red) were investigated. Neither O–H bond dissociation enthalpy nor ionization potential values of flavonoids correlated with ORAC values. The proton affinity (PA) and electron transfer enthalpy (ETE) values, which were obtained via the sequential proton-loss electron-transfer mechanism, were significantly associated with the ORACpyrogallol Red and ORACfluorescein assays, respectively. Thus, PA represented the kinetic aspect of RSA, whereas ETE reflected the RSA extent. The PA values and the most acidic sites of flavonoids were affected by intramolecular electronic interactions, H-bonding, 3-hydroxyl group in the C ring, and conjugation systems. The stability of the deprotonated flavonoid determined the ETE value. Apart from the PA and ETE values in the first oxidation step of flavonoids, the PA and ETE values in the second oxidation step also affected the ORAC values of flavonoids.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp307746c