Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO 80523, USA.
Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA.
Int J Mol Med. 2018 Jul;42(1):658-664. doi: 10.3892/ijmm.2018.3615. Epub 2018 Apr 3.
Quercetin has been demonstrated to produce DNA damage in the presence of metal ions. In the present study, 7 natural and 5 semi‑synthetic glycosylated flavonoids were utilized to investigate the cupric ion (Cu2+)‑dependent DNA damage in vitro. The reaction mixture, containing single‑stranded DNA, different concentrations of flavonoids and cupric ion in the buffer, was incubated at three different temperatures. DNA damage was then assessed by gel electrophoresis followed by densitometric analysis. The reaction mixture with quercetin at 4, 20 and 54˚C induced DNA damage in a concentration‑ and temperature‑dependent manner. Furthermore, only the reaction at 54˚C resulted in DNA damage in flavonoids with glucosyl substitution of the hydroxyl group at the 3‑position on the C ring in quercetin. By contrast, loss of the hydroxyl group at the 3‑position on the C ring, or at the 3'‑ or 4'‑position on the B ring of quercetin, did not portray DNA damage formation at the investigated experimental temperatures. In addition, the experimental results suggested that the hydroxyl group at the 3‑position on the C ring produced the strongest capability to induce DNA damage in the presence of cupric ions. Furthermore, hydroxyl groups at the 3'‑ or 4'‑position on the B ring were only able to induce DNA damage at higher temperatures, and were less efficient in comparison with the hydroxyl group at the 3‑position on the C ring. Cupric ion chelating capacity was also assessed with spectroscopic analysis, and quercetin presented the largest chelating capacity among the tested flavonoids. Hydroxyl radical formation was assessed with a luminol reaction, and quercetin presented faster consumption of luminol. These results suggest that the 3‑position hydroxyl group of the C ring is required to induce DNA damage at low temperatures. Furthermore, the results of the present study also indicated that the presence of cupric ions will decrease the activity of the glycosylated quercetins, in terms of their ability to induce DNA damage.
槲皮素在存在金属离子的情况下已被证明会造成 DNA 损伤。在本研究中，利用 7 种天然和 5 种半合成糖苷化类黄酮来研究铜离子（Cu2+）在体外对 DNA 的损伤作用。在含有单链 DNA、不同浓度黄酮类化合物和缓冲液中铜离子的反应混合物在三种不同温度下孵育。然后通过凝胶电泳和密度分析评估 DNA 损伤。在 4、20 和 54°C 下，槲皮素的反应混合物以浓度和温度依赖的方式诱导 DNA 损伤。此外，只有在 54°C 的反应中，在 C 环上 3 位羟基被葡萄糖基取代的黄酮类化合物才会导致 DNA 损伤。相比之下，C 环上 3 位的羟基缺失，或 C 环上 3'或 4'位的羟基缺失，在研究的实验温度下不会导致 DNA 损伤形成。此外，实验结果表明，C 环上 3 位的羟基在存在铜离子的情况下产生最强的诱导 DNA 损伤的能力。此外，B 环上 3'或 4'位的羟基仅能在较高温度下诱导 DNA 损伤，且与 C 环上 3 位的羟基相比效率较低。还通过光谱分析评估了铜离子螯合能力，槲皮素在测试的黄酮类化合物中表现出最大的螯合能力。通过发光氨反应评估了羟基自由基的形成，槲皮素对发光氨的消耗更快。这些结果表明，C 环上 3 位的羟基在低温下诱导 DNA 损伤是必需的。此外，本研究的结果还表明，铜离子的存在会降低糖苷化槲皮素诱导 DNA 损伤的能力。
