槲皮素与锌离子结合性质及抗氧化活性研究

目的 研究槲皮素与其锌离子（Zn²⁺）配合物的抗氧化性能。方法 通过紫外/可见分光光度法测定槲皮素与Zn²⁺的结合比例及结合常数，结合核磁共振技术确定其结合位点，以1，1-二苯基苯肼（DPPH）为探针，比较研究槲皮素与其Zn²⁺配合物的抗氧化性能。结果 当槲皮素中低于2个酚羟基被中和时，槲皮素与Zn²⁺的饱和结合比为2：1；当超过3个酚羟基被中和时，槲皮素与Zn²⁺的结合比为1：1，此时槲皮素-Zn²⁺的表观结合常数为2.42×10⁶ M^-1。槲皮素的3''-O、4''-O参与了与Zn²⁺的配位。槲皮素-Zn²⁺配合物清除DPPH自由基的活性比槲皮素本身高出2.3倍。结论 Zn²⁺可与槲皮素形成稳定的配合物，且其比槲皮素本身具有更高效的抗氧化性能，这为传统中药槲皮素的应用提供了新思路。

Studies on the binding properties of Zn2+ ion to quercetin and the antioxidant activities

Objective To study the anti-oxidation properties of Zn²⁺-quercetin complexes. Methods The binding stoichiometric ratios and the binding constant of Zn²⁺ to quercetin were measured with UV-Vis spectroscopy. The binding sites on quercetin were determined via ¹H NMR spectroscopy. The antioxidant activities of Zn²⁺-quercetin complexes were compared to quercetin by scavenging DPPH radical method. The binding ratio of Zn²⁺ to quercetin depends on neutralization of phenol groups of quercetin. Results The binding ratio of Zn²⁺ to quercetin is 1:2 when less than two OH groups were deprotonated. The binding ratio is 1:1 when more than three OH groups were deprotonated. The apparent binding constant is 2.42×10⁶ M^-1 for the 1:1 Zn²⁺-quercetin complex. The 3''-OH and 4''-OH of quercetin are involved in the Zn²⁺ binding. The scavenging DPPH radical activity of Zn²⁺-quercetin complex is 2.3 times of quercetin. Conclusion These results provide a new insight to expand applications of this traditional Chinese medicine.