Protocatechuic acid (3, 4-Dihydroxybenzoic acid) (3, 4-dihydroxybenzoic acid) is a natural phenolic compound found in many edible and medicinal plants. Recent studies indicate that it could be used as a protective agent against cardiovascular diseases and neoplasms. The mechanism of its action is mostly associated with antioxidant activity, including inhibition of generation as well as scavenging of free radicals and up-regulating enzymes which participate in their neutralization.

Methyl 3,4-dihydroxybenzoate (Protocatechuic acid methyl ester) is a major metabolite of antioxidant polyphenols found in green tea. Antioxidant and anti-inflammatory effect.