Photoelectron Spectroscopic and Computational Study of the Deprotonated Gallic Acid and Propyl Gallate Anions.

Antioxidants play important roles in eliminating reactive oxygen species (ROS), which have been associated with various degenerative diseases, such as cancer, aging, and inflammatory diseases. Gallic acid (GA) and propyl gallate (PG) are well-known antioxidants and have been widely studied in vitro and in vivo. The biological antioxidant abilities of GA and PG are related to the electronic structure of their dehydro-radicals. In this work, we report a combined photoelectron spectroscopic and computational study of the deprotonated gallic acid anion, [GA - H] - , and deprotonated propyl gallate anion, [PG - H] - . Adiabatic electron affinities of the dehydro-gallic acid radical, [GA - H]· and of the dehydro-propyl gallate radical, [PG - H]·, are measured to be 2.90 ± 0.05 eV and 2.85 ± 0.05 eV, respectively, and compared to computational results.