Abstract This study reports the synthesis and antibacterial evaluation of two novel complexes, [Cd (Q) (Bpy) (CH3COO)2, complex 1] and [Cd (Q) (Phen) (CH3COO)2, complex 2], based on quercetin ligand. The method of synthesis was by reacting natural flavonoid quercetin (Q) with a good chelator (Bpy = 2,2’-bipyridine, Phen= 1,10-phenanthroline and Q = quercetin) and metal ions. The produced metal complexes were studied in the solid state by Fourier-transform infrared (FTIR) spectroscopy and in solution by UV-Vis absorption. Further analysis included high resolution mass spectrometry (HRMS) for confirmation. To understand the nature and coordination of quercetin and its metal complexes, density functional theory (DFT) calculation was performed. The scavenging (DPPH radical), antibacterial, MTT, enzymatic and non-enzymatic antioxidant activity assay, cytotoxicity assay (fluorescence study) were done and quercetin was used for comparison. Both complex 1 and complex 2 induced loss of cell viability via impairment of metabolic activity, leakage of intracellular proteins, and increased oxidative stress. The free-radical scavenging activity of complex 2 (IC50 340.175 µg/mL) was statistically significantly more potent than that of complex 1. The MIC values of complex 2 (7.80 µg/mL Escherichia coli, 15.62 µg/mL Staphylococcus aureus) were higher as compared to complex 1 and quercetin in both test microorganisms. There was inhibition of cell proliferation in Escherichia coli treated with 2 µg/mL of complex 2, whereas Staphylococcus aureus did not show inhibition at this concentration. The cytotoxicity screening on MG 63 cell line showed that the compounds were safe up to 500 mg/L.

中文翻译：

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季镉 (II)-槲皮素复合物与 1,10-菲咯啉或 2,2'-联吡啶配体的合成、表征、抗菌和细胞毒性评估

摘要 本研究报告了两种新型复合物 [Cd (Q) (Bpy) (CH3COO)2, 复合物 1] 和 [Cd (Q) (Phen) (CH3COO)2, 复合物 2] 的合成和抗菌评价，基于槲皮素配体。合成方法是将天然黄酮类槲皮素 (Q) 与良好的螯合剂（Bpy = 2,2'-联吡啶，Phen = 1,10-菲咯啉和 Q = 槲皮素）和金属离子反应。通过傅里叶变换红外 (FTIR) 光谱法在固态下和在溶液中通过 UV-Vis 吸收研究生成的金属配合物。进一步的分析包括用于确认的高分辨率质谱 (HRMS)。为了了解槲皮素及其金属配合物的性质和配位，进行了密度泛函理论 (DFT) 计算。清除（DPPH自由基）、抗菌、MTT、酶促和非酶促抗氧化活性测定，进行细胞毒性试验（荧光研究）并使用槲皮素进行比较。复合物 1 和复合物 2 均通过代谢活性受损、细胞内蛋白质泄漏和氧化应激增加诱导细胞活力丧失。复合物 2 (IC50 340.175 µg/mL) 的自由基清除活性在统计学上显着高于复合物 1。复合物 2（7.80 µg/mL 大肠杆菌，15.62 µg/mL 金黄色葡萄球菌）的 MIC 值更高与两种测试微生物中的复合物 1 和槲皮素相比。在用 2 µg/mL 复合物 2 处理的大肠杆菌中，细胞增殖受到抑制，而金黄色葡萄球菌在该浓度下没有表现出抑制作用。对 MG 63 细胞系的细胞毒性筛选表明，化合物浓度高达 500 mg/L 时是安全的。