Polyphenols: well beyond the antioxidant capacity: gallic acid and related compounds as neuroprotective agents: you are what you eat!

Gallic acid (3,4,5-trihydroxybenzoic acid) is a phenolic acid widely distributed in many different families of higher plants, both in free state, and as a part of more complex molecules, such as ester derivatives or polymers. In nature, gallic acid and its derivatives are present in nearly every part of the plant, such as bark, wood, leaf, fruit, root and seed. They are present in different concentrations in common foodstuffs such as blueberry, blackberry, strawberry, plums, grapes, mango, cashew nut, hazelnut, walnut, tea, wine and so on. After consumption, about 70% of gallic acid is adsorbed and then excreted in the urine as 4-O-methylgallic acid. Differently, the ester derivatives of gallic acid, such as catechin gallate ester or gallotannins, are hydrolyzed to gallic acid before being metabolized to methylated derivatives. Gallic acid is a well known antioxidant compounds which has neuroprotective actions in different models of neurodegeneration, neurotoxicity and oxidative stress. In this review, we discuss about the neuroprotective actions of gallic acid and derivatives and their potential mechanisms of action.