Anthranilic acid as a secondary antioxidant: Implications to the inhibition of ^·OH production and the associated oxidative stress

The protection exerted by anthranilic acid against oxidative stress was investigated using the Density Functional Theory. It was found to be a rather poor primary antioxidant, not efficient as a peroxyl radical scavenger, albeit it may be able of scavenging other, more reactive, free radicals. On the contrary, it was found to be an excellent secondary antioxidant, through metal chelation. Anthranilic acid is proposed to be a proper ^·OH-inactivating ligand, with ways of action that depend on the strength of the reductant. It is able of chelating Cu(II) ions and fully prevent them from reduction by not too strong reductants such as the ascorbate ion. Accordingly, it is predicted to behave as an efficient antioxidant for in vitro experiments using Cu(II)-ascorbate mixtures as oxidant. On the other hand, anthranilic acid is able of downgrading the production of ^·OH in biological systems, where stronger reductants such as the superoxide radical anion are present, but only partially. However, under such conditions it would be efficient for deactivating this radical as it is formed through Fenton-like reactions. Accordingly, anthranilic would be an efficient protector against the ^·OH associated oxidative stress through its secondary antioxidant activity.