Food Science and Technology Programme, Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Republic of Singapore.
Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore , 117543 , Singapore.
J Agric Food Chem. 2019 Apr 17;67(15):4346-4354. doi: 10.1021/acs.jafc.8b06689. Epub 2019 Apr 8.
Dietary flavonoids are known as scavengers of reactive oxygen species such as hypochlorous acid. In spite of the abundant scavenging capacity data reported, few reports have addressed the relationship between the scavenging capacity and structures of different flavonoids. We characterized the reaction products of five flavonoids (apigenin, quercetin, naringenin, ampelopsin, and epicatechin) with hypochlorous acid and found that primary chlorination reaction occurred on the A-ring (C6 or C8) and/or C-rings but not on B-rings. Correlation of the hypochlorous acid scavenging capacity (IC values) and the structural features of flavonoids revealed that the hydroxyl groups in the A-ring and B-ring can enhance the scavenging capacity, whereas the C(2)C(3) double bond has a negative impact on the HClO scavenging capacity. Combining the SAR analysis and chemical study, we proposed that the reaction mechanism between flavonoids and HClO should be an electrophilic substitution reaction. Density functional theory (DFT) results are consistent with the selectivity of chlorination on the flavonoids. Our findings highlight the importance of considering specific reactive oxygen species when measuring radical scavenging capacity of dietary antioxidants.
膳食类黄酮是众所周知的活性氧（如次氯酸）清除剂。尽管已有大量的清除能力数据被报道，但很少有报道涉及不同类黄酮的清除能力与结构之间的关系。我们对五种类黄酮（芹菜素、槲皮素、柚皮苷、蛇葡萄素和表儿茶素）与次氯酸的反应产物进行了表征，发现主要的氯化反应发生在 A 环（C6 或 C8）和/或 C 环上，但不在 B 环上。次氯酸清除能力（IC 值）与类黄酮结构特征的相关性表明，A 环和 B 环上的羟基可以增强清除能力，而 C(2)C(3)双键对 HClO 的清除能力有负面影响。结合 SAR 分析和化学研究，我们提出了类黄酮与 HClO 之间的反应机制应该是亲电取代反应。密度泛函理论（DFT）的结果与类黄酮上氯化的选择性一致。我们的研究结果强调了在测量膳食抗氧化剂的自由基清除能力时，考虑特定活性氧的重要性。
