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

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.