Methyl-3-O-methyl gallate and gallic acid from the leaves of Peltiphyllum peltatum: isolation and comparative antioxidant, prooxidant, and cytotoxic effects in neuronal cells.

Methyl-3-O-methyl gallate (M3MG) is a rare natural product with close structural similarity to gallic acid. In the present report, the isolation of M3MG from Peltiphyllum peltatum leaves and its comparative antioxidant, prooxidant, and cytotoxicity to neuronal SH-SY5Y cells are discussed. When tested in concentrations up to 1 mM, M3MG consistently showed antioxidant activity without prooxidant effect both in cell and cell-free assay models. In contrast to M3MG, gallic acid showed a copper-dependent prooxidant effect that resulted in DNA damage, increased the level of intracellular reactive oxygen species, and induced cytotoxicity in neuronal cells. The identification of M3MG in P. peltatum leaves is furtherz evidence of the great antioxidant potential and nutritional value of the plant.