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.In Vitro: Vanillylmandelic acid has antioxidant activity, the IC50 value is determined as the amount of VMA required to reduce 50% of the starting concentration of free radical is 33*10-6 M in the UV-Vis decolourisation DPPH assay.In Vivo: Vanillylmandelic acid (intra-arterial injection over 1 min; 1, 10 and 100 mg/kg; the 60 min-observation period) produces a significant difference between vanillylmandelic acid groups and controls. Vanillylmandelic acid decreases the heart rate by 17.5%, 17.9% and 18.9% after 1, 10 and 100 mg/kg, respectively. Mean blood pressure is decreased by 13.5% in control animals as compared to 37%, 23% and 26% after 1, 10 and 100 mg/kg, respectively, in wistar rats.