Polyphenol Antioxidants Inhibit Peroxynitrite-Mediated DNA Damage In Vitro and in E. coli

Peroxynitrite causes oxidative DNA damage that can lead to cancer, cardiovascular, and neurodegenerative diseases. Polyphenol compounds have been extensively studied for their ability to prevent oxidative stress and DNA damage, but the cellular mechanisms for this behavior remain uncertain. We examined the ability of polyphenol compounds to inhibit peroxynitrite-mediated DNA damage in vitro and in Escherichia coli (AB1157) using gel electrophoresis, UV-vis spectroscopy, cellular DNA damage assays, and cell viability assays. Plasmid DNA gel electrophoresis studies show that polyphenols inhibit peroxynitrite-mediated DNA damage (IC₅₀ values of 13.4-1122 μM), activity that directly correlates with polyphenol redox potential. UV-vis kinetic studies also show peroxynitrite decomposition rates 2 to 27 times faster upon polyphenol addition. Polyphenols with gallol groups (IC₅₀ values of 13.4-158 μM) prevent significantly more DNA damage than their catechol analogs (IC₅₀ values of 68-1122 μM). Polyphenols with carboxylic acid groups decompose peroxynitrite five times faster than their methyl esters, indicating that carboxylate groups accelerate peroxynitrite decomposition. Polyphenol antioxidants also prevent cell death and cellular DNA damage upon peroxynitrite challenge in E. coli, confirming that polyphenols promote cell survival primarily by preventing DNA damage. This work represents the first combined in vitro and cellular study to determine the relationships between polyphenol structure and antioxidant prevention of peroxynitrite-mediated oxidative stress, information crucial for guiding studies of polyphenol antioxidant disease prevention.