黄杞苷保护DNA氧化损伤的活性及其可能机制

Protection Effect of Engeletin Towards DNA Against Oxidative Damage and Its Possible Mechanisms

关键词:  黄杞苷  自由基  DNA氧化  Fe²⁺络合  机制

Key words:  engeletin  free radical  DNA oxidative damage  Fe²⁺-binding  mechanism

摘要:

目的 研究黄杞苷保护DNA氧化损伤的活性与可能机制。方法 采用DNA保护分析法、超氧自由基（·O₂^-）清除法、Ferrozine显色法，探讨其保护DNA氧化损伤的活性与可能机制，并通过紫外可见光谱（UV-vis spectra）考察其与Fe²⁺络合的变化。结果 在DNA保护分析法、·O₂^-自由基清除法、Ferrozine显色法中，黄杞苷在一定浓度范围内，表现出浓度依赖性。其IC₅₀值分别（60.3±9.9），（44.5±7.6），（159.7±19.9）μg·mL^-1。UV-vis光谱分析表明，黄杞苷与Fe²⁺混合后，在波长475 nm处出现新的峰，摩尔消光系数为102.5 L·mol^-1·cm^-1。结论 黄杞苷能较好地保护DNA，免受羟基自由基（·OH）诱导的氧化损伤。其保护作用由直接清除ROS和间接清除ROS 2个途径实现。黄杞苷直接清除ROS，可能与氢转移和电子转移有关；间接清除ROS可能通过络合Fe²⁺的方式，阻断·OH自由基生成。不过，受3-位鼠李糖基的空间位阻影响，其Fe²⁺络合能力较弱。

Abstract:

OBJECTIVE To study engeletin's protective effect towards DNA against oxidative damage in vitro, and further to explore the possible mechanisms. METHODS Protective effect of engeletin was measured using DNA protection assay, ·O₂^--scavenging assay, and Fe²⁺-binding colorimetry assay. Its Fe²⁺-binding were also analyzed by UV-vis spectra. RESULTS In the DNA protection assay, ·O₂^--scavenging assay, and Fe²⁺-binding colorimetry assay, engeletin increased the percentages dose-dependently, and the IC₅₀ values were (60.3±9.9), (44.5±7.6), (159.7±19.9) μg·mL^-1, respectively. When engeletin mixed with Fe²⁺, there was a new peak at 475 nm with molar extinction coefficient 102.5 L·mol^-1·cm^-1 in UV-vis spectra. CONCLUSION Engeletin can effectively protect DNA from oxidative damage induced by ·OH. The protective effect may be fulfilled through direct ROS-scavenging which is via electron-transfer (ET) and H⁺-transfer (HAT) pathways, and indirect pathway (i.e. Fe²⁺-binding to blocking ·OH- production). However, its Fe²⁺-binding reaction is sterically hindered by the huge rhamnose residue at 3-position.