Final answer:
The principal urinary metabolite of adrenaline is vanillylmandelic acid (VMA), also referred to as 3-methoxy, 4-hydroxymandelic acid.
Step-by-step explanation:
The principal urinary metabolite of adrenaline, which is also known as epinephrine, is vanillylmandelic acid (VMA). This is the major excretory product of catecholamines and is formed through the metabolism of adrenaline by the enzymes Catechol-O-Methyl-Transferase (COMT) and Monoamine Oxidase (MAO) in the liver. These enzymes convert catecholamines into O-methylated and deaminated metabolites such as VMA.
Therefore, the correct answer to the question is D. 3-methoxy, 4-hydroxymandelic acid, which is another name for vanillylmandelic acid.