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

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• 作者：Di Zhang ; Yixiang Liu ; Le Chu ; Ying Wei ; Dan Wang ; Shengbao Cai ; Feng Zhou ; Baoping Ji
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：February 28, 2013
• 年：2013
• 卷：117
• 期：8
• 页码：1784-1794
• 全文大小：653K
• 年卷期：v.117,no.8(February 28, 2013)
• ISSN：1520-5215

文摘

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鈥揌 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 ORAC_{pyrogallol聽Red} and ORAC_fluorescein 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.