Vanillylmandelic acid, the end product of the metabolism of catecholamines, epinephrine, and norepinephrine, has antioxidant activity and is commonly used to help diagnose pheochromocytoma, as well as its elevation in association with depressive symptoms.

In Vitro Protein-tyrosine Kinase Assays: Recombinant Syk is expressed in baculovirus-infected St9 cells. Assays of recombinant Syk activity are carried out using angiotensin I peptide as substrate. The enzyme activities of recombinant Syk are measured by phosphorylation of angiotensin I peptide in the presence of various concentrations of Piceatannol.