Vanillylmandelic acid (VMA) is a chemical intermediate in the synthesis of artificial vanilla flavorings[1] and is an end-stage metabolite of the catecholamines (epinephrine, and norepinephrine).

VMA synthesis is the first step of a two-step process practiced by Rhodia since the 1970s to synthesize artificial vanilla.

[1] Specifically the reaction entails the condensation of guaiacol and glyoxylic acid in an ice cold, aqueous solution with sodium hydroxide.

VMA is found in the urine, along with other catecholamine metabolites, including homovanillic acid (HVA), metanephrine, and normetanephrine.

These hormones are released into the blood during times of physical or emotional stress, which are factors that may skew the results of the test.