Vanillylmandelic acid-d is the deuterium labeled Vanillylmandelic acid. Vanillylmandelic acid is the endproduct of epinephrine and norepinephrine metabolism. Vanillylmandelic acid can be used as an indication of the disorder in neurotransmitter metabolism as well. Vanillylmandelic acid has antioxidant activity towards DPPH radical with an IC50 value of 33 μM[1].