Free radical scavenging activity of gallic acid toward various reactive oxygen, nitrogen, and sulfur species: a DFT approach.

Gallic acid is a well-recognized naturally occurring compound possessing antioxidant activities. The free radical scavenging ability of gallic acid for fifty reactive species, such as oxygen, nitrogen, and sulfur-containing species, has been studied using the formal hydrogen atom transfer mechanism. The theoretical studies have been conducted in the gas phase and aqueous solution at M05-2X/6-311++G** level using the density functional theory (DFT) calculations. The relative damaging potential of all the reactive species has been compared by investigating their hydrogen atom and electron affinity. Furthermore, a comparison of their relative reactivity was made by evaluating several global chemical reactivity descriptors. Additionally, the feasibility of scavenging the species by gallic acid has been studied by computing the redox potentials and equilibrium constants for the overall process in the aqueous solution.